The Shape Expressions (ShEx) language describes RDF nodes and graph structures. A node constraint describes an RDF node (IRI, blank node or literal) and a shape describes the triples involving nodes in an RDF graph. These descriptions identify predicates and their associated cardinalities and datatypes. ShEx shapes can be used to communicate data structures associated with some process or interface, generate or validate data, or drive user interfaces.
This document defines the ShEx language. See the Shape Expressions Primer for a non-normative description of ShEx.
This document has been developed by the Shape Expressions Community Group. The specification has undergone significant development since the 1.0 version.
This version of the document represents a Candidate Release, with stable features. Comments and implementations are solicited prior to an eventual Final 2.0 Release.
The Shape Expressions language is expected to remain stable with the exception of:
The Shape Expressions (ShEx) language provides a structural schema for RDF data. This can be used to document APIs or datasets, aid in development of API-conformant messages, minimize defensive programming, guide user interfaces, or anything else that involves a machine-readable description of data organization and typing requirements.
ShEx describes RDF graph [[RDF11-CONCEPTS]] structures as sets of potentially connected Shapes.
These constrain the triples involving nodes in an RDF graph.
Node Constraints constrain RDF nodes by constraining their node kind (IRI, blank node or Literal), enumerating permissible values in value sets, specifying their datatype, and constraining value ranges of Literals.
Additionally, they constrain lexical forms of Literals, IRIs and labeled blank nodes.
Shape Expressions schemas share blank nodes with the constrained RDF graphs in the same way that graphs in RDF datasets [[!rdf11-concepts]] share blank nodes.
ShEx can be represented in JSON structures (ShExJ) or a compact syntax (ShExC). The compact syntax is intended for human consumption; the JSON structure for machine processing. This document defines ShEx in terms of ShExJ and includes a section on the ShEx Compact Syntax (ShEx).
The JSON [[!rfc4627]] Syntax serves as a serializable proxy for an abstract syntax. This specification uses a simple grammar to describe the set of JSON documents that can be interpreted as a ShEx schema.
typeName is the name of the typed data structure.
Types are referenced in the definitions of object members and in the definitions of the semantics for those data structures.member* is a list of zero or more terminals or references to other typeExpressions.Terminals are JSON strings and are indicated by all-caps, e.g. IRI.
For brevity, RDF nodes are represented as JSON strings composed as:
"http://example.org/resource"_:" and a blank node identifier, e.g. "_:blank3""'), the lexical form of the literal, U+0022, and the first matching of:
http://www.w3.org/2001/XMLSchema#string: empty string, e.g. "abc".@') and the language tag, e.g. "\"hello world\"@en-US"^^') and the lexical form of the datatype URI, e.g. "\"123\"^^http://www.w3.org/2001/XMLSchema#integer"typeExpression is one of:
typeName — an object of corresponding typearray: [ typeExpression+ ]— an array of one or more JSON values matching the typeExpression.choice: typeExpression1 | typeExpression2 | …— a choice between two or more typeExressions.?, +, * following the notation in the XML specification[[!XML]] or {m,} to indicate a that at least m elements are required.In javascript-enabled browsers, schemas with a button can be converted between the JSON representation and the compact syntax by clicking the button. The button text indicates the currently shown representation. Selecting the example and pressing "j" or "c" converts the example to the JSON (ShExJ) or compact form (ShExC). Pressing "shift J" or "shift C" converts all such examples to ShExJ or ShExC.
The following examples are excerpts from the definitions below. In the JSON notation,
signifies that a Schema has three optional components called startActs, start and shapes:
signifies that a shapeExpr is one of seven object types: ShapeOr | ShapeAnd | ….
signifies that a NodeConstraint has a nodeKind of one of the four literals followed by any number of xsFacet and an xsFacet is either a stringFacet or a numericFacet.
ShExJ is a dialect of JSON-LD [[!JSON-LD]] and the member id is used as a node identifier.
An object may be represented inline or referenced by its id which may be either a blank node or an IRI.
The JSON structure may include references to shapes and triples:
An object with a circular reference must be referenced by id. This example uses a nested shape reference on a value expression (defined below).
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint", "predicate": "http://schema.example/related",
"valueExpr": "http://schema.example/IssueShape", min: 0 } } ] }
Not captured in this JSON syntax definition is the rule that every shapeExpr referenced by a schema's shapes must have an id and no other shapeExpr may have an id. The JSON syntax definitition simplifies this by adding id:shapeExprLabel? to every shapeExpr.
JSON examples are rendered in a .json CSS style. Partial examples include ranges in a .comment CSS style to indicate text which would be substituted in a complete example. For example { "type": "ShapeAnd", "shapeExprs": [ SE1, … ] } indicates that both SE1 and … would be substituted in a complete example.
The validation process defined in this document relies on matching triple patterns in the form (subject, predicate, object) where each position may be supplied by a constant, a previously defined term, or the underscore "_", which represents a previously undefined element or wildcard.
This corresponds to a SPARQL Triple Pattern where each "_" is replaced by a unique blank node.
Matching such a triple pattern against a graph is defined by SPARQL Basic Graph Pattern Matching (BGP) with a BGP containing only that triple pattern.
ShEx validation results may be reported as an annotated ShapeMap. For illustration purposes in this specification, results of validation are represented in a table associating node/shape pairs with a pass or fail and a reason for failure:
| shape | node | result | reason |
|---|---|---|---|
| <Shape1> | <node1> | pass | |
| <Shape1> | <node2> | fail | no ex:state supplied. |
Shape expressions are defined using terms from RDF semantics [[!rdf11-mt]]:
This specification makes use of the following namespaces:
foaf:http://xmlns.com/foaf/0.1/rdf:http://www.w3.org/1999/02/22-rdf-syntax-ns#rdfs:http://www.w3.org/2000/01/rdf-schema#shex:http://www.w3.org/ns/shex#xsd:http://www.w3.org/2001/XMLSchema#The following functions access the elements of an RDF graph G containing a node n:
Consider the RDF graph G represented in Turtle:
PREFIX ex: http://schema.example/
PREFIX inst: http://inst.example/#
PREFIX foaf: http://xmlns.com/foaf/
PREFIX xsd: http://www.w3.org/2001/XMLSchema#
inst:Issue1
ex:state ex:unassigned ;
ex:reportedBy _:User2 .
_:User2
foaf:name "Bob Smith" ;
foaf:mbox <mailto:bob@example.org> .
There are two arcs out of _:User2; arcsOut(G, _:User2):
_:User2 foaf:name "Bob Smith" .
_:User2 foaf:mbox <mailto:bob@example.org> .
There is one arc into _:User2; arcsIn(G, _:User2):
inst:Issue1 ex:reportedBy _:User2 .
There are three arcs in the neighbourhood of _:User2 set, neigh(G, _:User2):
_:User2 foaf:name "Bob Smith" .
_:User2 foaf:mbox <mailto:bob@example.org> .
inst:Issue1 ex:reportedBy _:User2 .
Conformance criteria are relevant to authors and authoring tool implementers. As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
A Shape Expressions (ShEx) schema is a collection of labeled Shapes and Node Constraints. These can be used to describe or test nodes in RDF graphs. ShEx does not prescribe a language for associating nodes with shapes but several approaches are described in the ShEx Primer.
A shapes schema is captured in a Schema object:
where shapes is a mapping from shape label to shape expression.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape", … },
{ "id": "_:UserShape", … },
{ "id": "http://schema.example/EmployeeShape", … } ] }
ex:IssueShape { … }
_:UserShape { … }
ex:EmployeeShape { … }
A fixed ShapeMap is a set of pairs of a nodeSelector, an RDF node) and shapeLabel, a shape expression identifier.
The shapeLabel member is either a shapeExprLabel or the token "START" to identify the start shape expression.
When used as an argument to isValid, a nodeSelector/shapeLabel association in a ShapeMap indicates that the validation process should test whether nodeSelector satisfies the constraint given by the definition of the shapeExpr labeled by shapeLabel.
isValid: The expression isValid(G, m) indicates that for every node/shape pair (n, s) in m, s has a corresponding shape expression se and satisfies(n, se, G, m).
satisfies is defined below for each form of shape expression.
Validation of a graph G does not necessarily require the construction of a ShapeMap with every node in G. The validation semantics defined below imply a set of dependencies for validating some node as a shape. A validation process that tests every node in a graph against every shape in a schema can be considered to have an input ShapeMap associating each node with the set of all shapes in the schema.
The semantics of ShEx are independent from the construction of an input ShapeMap. https://www.w3.org/2001/sw/wiki/ShEx/ShapeMap has list of popular methods for constructing ShapeMaps.
Validation of a node against a shape in a schema requires that there is a consistent mapping from node to shape for every node and shape visited during a validation process. The remainder of this document uses m to indicate such a mapping.
A shape expression is composed of four kinds of objects combined with the algebraic operators And, Or and Not:
| shapeExpr | = | ShapeOr | ShapeAnd | ShapeNot | NodeConstraint | Shape | ShapeExternal | shapeExprRef ; |
|---|---|---|
| ShapeOr | { | id:shapeExprLabel? shapeExprs:[shapeExpr] } |
| ShapeAnd | { | id:shapeExprLabel? shapeExprs:[shapeExpr] } |
| ShapeNot | { | id:shapeExprLabel? shapeExpr:shapeExpr } |
| ShapeExternal | { | id:shapeExprLabel? } |
| shapeExprRef | = | shapeExprLabel ; |
| shapeExprLabel | = | IRI | BNODE ; |
Examples of shape expressions:
{ "type": "Shape", … }
{ … }
{ "type": "ShapeAnd", "shapeExprs": [
{ "type": "NodeConstraint", "nodeKind": "iri" },
{ "type": "ShapeOr", "shapeExprs": [
"http://schema.example/IssueShape",
{ "type": "ShapeNot", "shapeExpr": { "type": "Shape", … } }
] } ] }
IRI AND ( @<http://schema.example/IssueShape> OR NOT { … } )
In this ShapeOr's shapeExprs,"http://schema.example/IssueShape" is a reference to the shape expression with the id "http://schema.example/IssueShape".
satisfies: The expression satisfies(n, se, G, m) indicates that a node n and graph G satisfy a shape expression se with shapeMap m.
notSatisfies: Conversely, notSatisfies(n, se, G, m) indicates that n and G do not satisfy se with the given shapeMap m.
notSatisfies(n, se, G, _) indicates that no shapeMap would allow n and G to satisfy se.
satisfies(n, se, G, m) is true if and only if:
satisfies2(n, se) as described below in Node Constraints.
Note that testing if a node satisfies a node constraint does not require a graph or shapeMap.satisfies(n, se) as defined below in Shapes and Triple Expressions.satisfies(n, se2, G, m).satisfies(n, se2, G, m).notSatisfies(n, se2, G, m).satisfies(n, se2, G, m).Given the three shape expressions SE1, SE2, SE3 in a Schema Sch, such that:
satisfies(n, SE1, G, m)satisfies(n, SE2, G, m)notSatisfies(n, SE3, G, m)the following hold:
{ "type": "ShapeAnd", "shapeExprs": [ SE1, SE2 ] }{ "type": "ShapeOr", "shapeExprs": [ SE1, SE2, SE3 ] }{ "type": "ShapeNot", "shapeExpr": {
{ "type": "ShapeOr", "shapeExprs": [
SE1,
{ "type": "ShapeAnd", "shapeExprs": [ SE2, SE3 ] }
] }
} }
If Sch's shapes maps "http://schema.example/shape1" to SE1 then the following holds:
http://schema.example/shape1"
| NodeConstraint | { | id:shapeExprLabel? nodeKind:("iri" | "bnode" | "nonliteral" | "literal")? datatype:IRI? xsFacet* values:[valueSetValue]? } |
|---|---|---|
| xsFacet | = | stringFacet | numericFacet ; |
| stringFacet | = | ("length"|"minlength"|"maxlength"):INTEGER | pattern:STRING flags:STRING? ; |
| numericFacet | = | ("mininclusive"|"minexclusive"|"maxinclusive"|"maxexclusive"):numericLiteral |
| | | ("totaldigits"|"fractiondigits"):INTEGER ; | |
| numericLiteral | = | INTEGER | DECIMAL | DOUBLE ; |
| valueSetValue | = | objectValue | IriStem | IriStemRange | LiteralStem | LiteralStemRange | LanguageStem | LanguageStemRange ; |
| objectValue | = | IRI | ObjectLiteral ; |
| IriStem | { | stem:IRI } |
| IriStemRange | { | stem:(IRI | Wildcard) exclusions:[objectValue|IriStem +]? } |
| LiteralStem | { | stem:ObjectLiteral } |
| LiteralStemRange | { | stem:(ObjectLiteral | Wildcard) exclusions:[objectValue|LiteralStem +]? } |
| LanguageStem | { | stem:ObjectLiteral } |
| LanguageStemRange | { | stem:(ObjectLiteral | Wildcard) exclusions:[objectValue|LanguageStem +]? } |
| Wildcard | { | /* empty */ } |
For a node n and constraint nc, satisfies2(n, nc) if and only if for every nodeKind, datatype, xsFacet and values constraint value v present in nc nodeSatisfies(n, v).
The following sections define nodeSatisfies for each of these types of constraints:
For a node n and constraint value v, nodeSatisfies(n, v) if:
The following examples use a TripleConstraint object described later in the document. The
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint", "predicate": "http://schema.example/state",
"valueExpr": { "type": "NodeConstraint", "nodeKind": "iri" } } } ] }
ex:IssueShape {
ex:state IRI
}
<issue1> ex:state ex:HunkyDory . <issue2> ex:taste ex:GoodEnough . <issue3> ex:state "just fine" .
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue1> | pass | |
| <IssueShape> | <issue2> | fail | expected 1 ex:state property. |
| <IssueShape> | <issue3> | fail | ex:state expected to be an IRI, literal found. |
Note that <issue2> fails not because of a nodeKind violation but instead because of a Cardinality violation described below.
For a node n and constraint value v, nodeSatisfies(n, v) if n is an Literal with the datatype v and, if v is in the set of SPARQL operand data types[[!sparql11-query]], an XML schema string with a value of the lexical form of n can be cast to the target type v per XPath Functions 3.1 section 19 Casting[[!xpath-functions]].
Only datatypes supported by SPARQL MUST be tested but ShEx extensions MAY add support for other datatypes.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint", "predicate": "http://schema.example/submittedOn",
"valueExpr": {
"type": "NodeConstraint",
"datatype": "http://www.w3.org/2001/XMLSchema#date"
} } } ] }
ex:IssueShape {
ex:submittedOn xsd:date
}
<issue1> ex:submittedOn "2016-07-08"^^xsd:date . <issue2> ex:submittedOn "2016-07-08T01:23:45Z"^^xsd:dateTime . <issue3> ex:submittedOn "2016-07"^^xsd:date .
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue1> | pass | |
| <IssueShape> | <issue2> | fail | ex:submittedOn expected to be an xsd:date, xsd:dateTime found. |
| <IssueShape> | <issue3> | fail | 2016-07 is not a valid xsd:date. |
In RDF 1.1, language-tagged strings[[!rdf11-concepts]] have the datatype http://www.w3.org/1999/02/22-rdf-syntax-ns#langString.
RDF 1.0 included RDF literals with no datatype or language tag.
These are called "simple literals" in SPARQL11[[!sparql11-query]].
In RDF 1.1, these literals have the datatype http://www.w3.org/2001/XMLSchema#string.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://www.w3.org/2000/01/rdf-schema#label",
"valueExpr": {
"type": "NodeConstraint",
"datatype": "http://www.w3.org/1999/02/22-rdf-syntax-ns#langString"
} } } ] }
ex:IssueShape {
rdfs:label rdf:langString
}
<issue3> rdfs:label "emits dense black smoke"@en .
<issue4> rdfs:label "unexpected odor" .
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue3> | pass | |
| <IssueShape> | <issue4> | fail | rdfs:label expected to be an rdf:langString, xsd:string found. |
String facet constraints apply to the lexical form of the RDF Literals and IRIs and blank node identifiers (see note below regarding access to blank node identifiers).
Let lex =
Let len = the number of unicode codepoints in lex
For a node n and constraint value v, nodeSatisfies(n, v):
length" constraints, v = len,minlength" constraints, v >= len,maxlength" constraints, v <= len,pattern" constraints, v is unescaped into a valid XPath 3.1 regular expression[[!xpath-functions-31]] re and invoking fn:matches(lex, re) returns fn:true.
If the flags parameter is present, it is passed as a third argument to fn:matches.
The pattern may have XPath 3.1 regular expression escape sequences per the modified production [10] in section 5.6.1.1 as well as numeric escape sequences of the form 'u' HEX HEX HEX HEX or 'U' HEX HEX HEX HEX HEX HEX HEX HEX.
Unescaping replaces numeric escape sequences with the corresponding unicode codepoint.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/submittedBy",
"valueExpr": { "type": "NodeConstraint", "minlength": 10 } } } ] }
ex:IssueShape {
ex:submittedBy MINLENGTH 10
}
<issue1> ex:submittedBy <http://a.example/bob> . # 20 characters <issue2> ex:submittedBy "Bob" . # 3 characters
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue1> | pass | |
| <IssueShape> | <issue2> | fail | ex:submittedBy expected to be >= 10 characters,3 characters found. |
Access to blank node identifiers may be impossible or unadvisable for many use cases. For instance, the SPARQL Query and SPARQL Update languages treat blank nodes in the query, labeled or otherwise, as variables. Lexical constraints on blank node identifiers can only be implemented in systems which preserve such labels on data import.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/submittedBy",
"valueExpr": { "type": "NodeConstraint",
"pattern": "genuser[0-9]+", "flags": "i" }
} } ] }
ex:IssueShape {
ex:submittedBy ~/genuser[0-9]+/i
}
<issue6> ex:submittedBy _:genUser218 .
<issue7> ex:submittedBy _:genContact817 .
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue6> | pass | |
| <IssueShape> | <issue7> | fail | _:genContact817 expected to match genuser[0-9]+. |
When expressed as JSON strings, regular expressions are subject to the JSON string escaping rules.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/ProductShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/trademark",
"valueExpr": { "type": "NodeConstraint",
"pattern": "^/\\t\\\\\\U0001D4B8\\?$" }
} } ] }
ex:ProductShape {
ex:trademark /^\/\t\\\U0001D4B8\?$/
}
<product6> ex:trademark " \\𝒸?" . <product7> ex:trademark "\t\\\U0001D4B8?" . # Turtle literals have escape characters [tbnrf"'\]. <product8> ex:trademark "\t\\\\U0001D4B8?" .
| shape | node | result | reason |
|---|---|---|---|
| <ProductShape> | <product6> | pass | |
| <ProductShape> | <product7> | pass | |
| <ProductShape> | <product8> | fail | found "\U0001D4B8" instead of "𝒸" (codepoint U+1D4B8). |
Numeric facet constraints apply to the numeric value of RDF Literals with datatypes listed in SPARQL 1.1 Operand Data Types[[!sparql11-query]].
Numeric constraints on non-numeric values fail.
totaldigits and fractiondigits constraints on values not derived from xsd:decimal fail.
Let num be the numeric value of n.
For a node n and constraint value v, nodeSatisfies(n, v):
mininclusive" constraints, v <= num,minexclusive" constraints, v < num,maxinclusive" constraints, v >= num,maxexclusive" constraints, v > num,totaldigits" constraints, v equals the number of digits in the XML Schema canonical form[[!xmlschema-2]] of the value of n,fractiondigits" constraints, v is less than or equals the number of digits to the right of the decimal place in the XML Schema canonical form[[!xmlschema-2]] of the value of n, ignoring trailing zeros.The operators <=, <, >= and > are evaluated after performing numeric type promotion[[!xpath20]].
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/confirmations",
"valueExpr": { "type": "NodeConstraint", "mininclusive": 1 } } } ] }
ex:IssueShape {
ex:confirmations MININCLUSIVE 1
}
<issue1> ex:confirmations 1 . <issue2> ex:confirmations 2^^xsd:byte . <issue3> ex:confirmations 0 . <issue4> ex:confirmations "ii"^^ex:romanNumeral .
| shape | node | result | reason |
|---|---|---|---|
| <IssueShape> | <issue1> | pass | |
| <IssueShape> | <issue2> | pass | |
| <IssueShape> | <issue3> | fail | 0 is less than 1. |
| <IssueShape> | <issue4> | fail | ex:romanNumeral is not a numeric datatype. |
The nodeSatisfies semantics for NodeConstraint values depends on a nodeIn function defined below.
For a node n and constraint value v, nodeSatisfies(n, v) if n matches some valueSetValue vsv in v.
A term matches a valueSetValue if:
nodeIn: asserts that an RDF node n is equal to an RDF term s or is in a set defined by a IriStem, LiteralStem or LanguageStem.
The expression nodeIn(n, s) is satisfied if:
NoActionIssueShape requires a state of Resolved or Rejected:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/NoActionIssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/state",
"valueExpr": {
"type": "NodeConstraint", "values": [
"http://schema.example/Resolved",
"http://schema.example/Rejected" ] } } } ] }
ex:NoActionIssueShape {
ex:state [ ex:Resolved ex:Rejected ]
}
<issue1> ex:state ex:Resolved .
<issue2> ex:state ex:Unresolved .
| shape | node | result | reason |
|---|---|---|---|
| <NoActionIssueShape> | <issue1> | pass | |
| <NoActionIssueShape> | <issue2> | fail | ex:state expected to be ex:Resolved or ex:Rejected, ex:Unresolved found. |
An employee must have an email address that is the string "N/A" or starts with "engineering-" or "sales-" but not "sales-contacts" or "sales-interns":
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/EmployeeShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/mbox",
"valueExpr": {
"type": "NodeConstraint", "values": [
{"value": "N/A"},
{ "type": "IriStemRange", "stem": "mailto:engineering-" },
{ "type": "IriStemRange", "stem": "mailto:sales-", "exclusions": [
{ "type": "IriStem", "stem": "mailto:sales-contacts" },
{ "type": "IriStem", "stem": "mailto:sales-interns" }
] }
] } } } ] }
ex:EmployeeShape {
foaf:mbox [ "N/A"
<mailto:engineering->~
<mailto:sales->~
- <mailto:sales-contacts>~
- <mailto:sales-interns>~ ]
}
<issue3> foaf:mbox "N/A" . <issue4> foaf:mbox <mailto:engineering-2112@a.example> . <issue5> foaf:mbox <mailto:sales-835@a.example> . <issue6> foaf:mbox "missing" . <issue7> foaf:mbox <mailto:sales-contacts-999@a.example> .
| shape | node | result | reason |
|---|---|---|---|
| <EmployeeShape> | <issue3> | pass | |
| <EmployeeShape> | <issue4> | pass | |
| <EmployeeShape> | <issue5> | pass | |
| <EmployeeShape> | <issue6> | fail | "missing" is not in value set. |
| <EmployeeShape> | <issue7> | fail | <mailto:sales-contacts-999@a.example> is excluded. |
An employee must not have an email address that starts with "engineering-" or "sales-":
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/EmployeeShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/mbox",
"valueExpr": {
"type": "NodeConstraint", "values": [
{ "type": "IriStemRange", "stem": {"type": "Wildcard"},
"exclusions": [
{ "type": "IriStem", "stem": "mailto:engineering-" },
{ "type": "IriStem", "stem": "mailto:sales-" }
] }
] } } } ] }
ex:EmployeeShape {
foaf:mbox [ . - <mailto:engineering->~ - <mailto:sales->~ ]
}
<issue8> foaf:mbox 123 .
<issue9> foaf:mbox <mailto:core-engineering-2112@a.example> .
<issue10> foaf:mbox <mailto:engineering-2112@a.example> .
| shape | node | result | reason |
|---|---|---|---|
| <EmployeeShape> | <issue8> | pass | |
| <EmployeeShape> | <issue9> | pass | |
| <EmployeeShape> | <issue10> | fail | <mailto:engineering-2112@a.example> is excluded. |
A value set can have a single value in it. This is used to indicate that a specific value is required, e.g. that an ex:state must be equal to <http://schema.example/Resolved> or the rdf:type of some node must be foaf:Person.
Triple expressions are used for defining patterns composed of triple constraints. Shapes associate triple expressions with flags indicating whether triples match if they do not correspond to triple constraints in the triple expression. A triple expression is composed of TripleConstraint and tripleExprRef objects composed with grouping and choice operators.
| Shape | { | id:shapeExprLabel? closed:BOOL? extra:[IRI]? expression:tripleExpr? semActs:[SemAct]? } |
|---|---|---|
| tripleExpr | = | EachOf | OneOf | TripleConstraint | tripleExprRef ; |
| EachOf | { | id:tripleExprLabel? expressions:[tripleExpr] min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } |
| OneOf | { | id:tripleExprLabel? expressions:[tripleExpr] min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } |
| TripleConstraint | { | id:tripleExprLabel? inverse:BOOL? predicate:IRI valueExpr:shapeExpr? min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } |
| tripleExprRef | = | tripleExprLabel ; |
| tripleExprLabel | = | IRI | BNODE ; |
The satisfies semantics for a Shape depend on a matches function defined below.
For a node n, shape S, graph G, and shapeMap m, satisfies(n, S, G, m) if and only if:
neigh(G, n) can be partitioned into two sets matched and remainder such that matches(matched, expression, m).
If expression is absent, remainder = neigh(G, n).outs = remainder ∩ arcsOut(G, n).matchables = Ø (the empty set).matchables ∪ unmatchables = outs.
matches: asserts that a triple expression is matched by a set of triples that come from the neighbourhood of a node in an RDF graph.
The expression matches(T, expr, m) indicates that a set of triples T can satisfy these rules:
expr has semActs and matches(T, expr, m) by the remaining rules in this list and the evaluation of semActs succeeds according to the section below on Semantic Actions.
{ "type": "OneOf", "shapeExprs": [te1, te2, …], "min": 2, "max": 3,
"semActs": [SemAct1, SemAct2, …] }
(te1 | te2 …) {2,3} %<SemAct1>% %<SemAct2>% …
{ "type": "OneOf", "shapeExprs": [te1, te2, …], "min": 2, "max": 3 }
(te1 | te2 …) {2,3}
expr has a cardinality of min and/or max not equal to 1, where a max of -1 is treated as unbounded, and T can be partitioned into k subsets T1, T2,…Tk such that min ≤ k ≤ max and for each Tn, matches(Tn, expr, m) by the remaining rules in this list.
{ "type": "OneOf", "shapeExprs": [te1, te2, …], "min": 2, "max": 3 }
(te1 | te2 …) {2,3}
{ "type": "OneOf", "shapeExprs": [te1, te2, …] }
(te1 | te2 …)
expr is a OneOf and there is some shape expression se2 in shapeExprs such that a matches(T, se2, m).
{ "type": "OneOf", "shapeExprs": [
{ "type": "EachOf", "shapeExprs": [te3, te4, …] },
{ "type": "TripleExpression", "min": 1, "max": -1,
"predicate": "http://xmlns.com/foaf/0.1/name" }
] }
(te3 ; te4 ; …) | <http://xmlns.com/foaf/0.1/name> . +
{ "type": "EachOf", "shapeExprs": [te3, te4, …] }
te3 ; te4 ; …
{ "type": "TripleExpression", "min": 1, "max": -1,
"predicate": "http://xmlns.com/foaf/0.1/name" }
<http://xmlns.com/foaf/0.1/name> . +
expr is an EachOf and there is some partition of T into T1, T2,… such that for every expression expr1, expr2,… in shapeExprs, matches(Tn, exprn, m).
{ "type": "EachOf", "shapeExprs": [
{ "type": "TripleExpression",
"predicate": "http://xmlns.com/foaf/0.1/givenName" },
{ "type": "TripleExpression",
"predicate": "http://xmlns.com/foaf/0.1/familyName" }
] }
<http://xmlns.com/foaf/0.1/givenName> . ; <http://xmlns.com/foaf/0.1/familyName> .
{ "type": "TripleExpression",
"predicate": "http://xmlns.com/foaf/0.1/givenName" }
<http://xmlns.com/foaf/0.1/givenName> .
{ "type": "TripleExpression",
"predicate": "http://xmlns.com/foaf/0.1/familyName" }
<http://xmlns.com/foaf/0.1/familyName> .
expr is a TripleConstraint and:
expr has no valueExpr
{ "type": "TripleExpression",
"predicate": "http://xmlns.com/foaf/0.1/givenName" }
<http://xmlns.com/foaf/0.1/givenName> . ;
http://xmlns.com/foaf/0.1/givenName"or satisfies(value, valueExpr, G, m).
{ "type": "TripleConstraint", "inverse": true,
"predicate": "http://purl.org/dc/elements/1.1/author",
"valueExpr": "http://schema.example/IssueShape" }
^<http://purl.org/dc/elements/1.1/author>
@<http://schema.example/IssueShape>
expr is an tripleExprRef and satisfies(value, tripleExprWithId(tripleExprRef), G, m).
The tripleExprWithId function is defined in Triple Expression Reference Requirement below.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/EmployeeShape",
"type": "Shape", "expression": {
"type": "EachOf", "expressions": [
"http://schema.example/nameExpr",
{ "type": "TripleConstraint",
"predicate": "http://schema.example/empID",
"valueExpr": { "type": "NodeConstraint",
"datatype": "http://www.w3.org/2001/XMLSchema#integer" } } ] } },
{ "id": "http://schema.example/PersonShape",
"type": "Shape", "expression": {
"id": "http://schema.example/nameExpr",
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/name" } } ] }
<http://schema.example/EmployeeShape> {
&<http://schema.example/nameExpr> ;
<http://schema.example/empID>
<http://www.w3.org/2001/XMLSchema#integer>
}
<http://schema.example/PersonShape> {
$<http://schema.example/nameExpr>
<http://xmlns.com/foaf/0.1/name> ;
}
"http://schema.example/PersonShape"
http://schema.example/PersonShape"The semantics defined above assume two structural requirements beyond those imposed by the grammar of the abstract syntax. These ensure referential integrity and eliminate logical paradoxes such as those that arrise through the use of negation. These are not constraints expressed by the schema but instead those imposed on the schema.
A graph G is said to conform with a schema S with a ShapeMap m when:
An shapeExprRef MUST appear in the schema's shapes map and the corresponding triple expression MUST be a Shape with a shapeExpr.
The function shapeExprWithId(shapeExprRef) returns the shape's shapeExpr.
Following are two valid shapeExprRefs:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/PersonShape",
"type":"Shape", "expression": {
"id": "http://schema.example/nameExpr",
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/name"
} },
{ "id": "http://schema.example/EmployeeShape", "type":"EachOf", "shapeExprs": [
"http://schema.example/nameExpr",
{
"type":"Shape", "expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/employeeNumber" }
} ] } ] }
ex:PersonShape {
foaf:name .
}
ex:EmployeeShape ex:PersonShape AND {
ex:employeeNumber .
}
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/PersonShape",
"type":"Shape", "expression": {
"id": "http://schema.example/nameExpr",
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/name"
} },
{ "id": "http://schema.example/EmployeeShape",
"type":"Shape", "expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/dependent",
"valueExpr": "http://schema.example/PersonShape" } } ] }
ex:PersonShape {
foaf:name .
}
ex:EmployeeShape {
ex:dependent ex:PersonShape*
}
This shapeExprRef is invalid because there is no corresponding shape expression:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/S1",
"type":"Shape", "expression":
"http://schema.example/MissingShapeExpr"
} ] }
S1 {
&MissingShapeExpr
}
This shapeExprRef is invalid because the referenced object is a triple expression instead of a shape expression:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/CustomerShape",
"type":"Shape", "expression": { "type": "TripleConstraint",
"id": "http://schema.example/discountExpr",
"predicate": "http://schema.example/discount" } },
{ "id": "http://schema.example/EmployeeShape",
"type":"Shape", "expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/contactFor",
"valueExpr": "http://schema.example/CustomerShape"
} } ] }
ex:CustomerShape {
$ex:discountExpr ex:discount .
}
ex:EmployeeShape {
ex:contactFor @ex:CustomerShape
}
An tripleExprRef MUST identify a triple expression in the schema.
The function tripleExprWithId(tripleExprRef) returns the triple expression with the id tripleExprRef.
Following is a valid triple expression reference:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/PersonShape",
"type":"Shape", "expression": {
"id": "http://schema.example/nameExpr",
"type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/name"
} },
{ "id": "http://schema.example/EmployeeShape",
"type":"Shape", "expression": { "type":"EachOf", "shapeExprs": [
"http://schema.example/nameExpr",
{ "type": "TripleConstraint",
"predicate": "http://schema.example/employeeNumber" }
] } } ] }
ex:PersonShape {
foaf:name .
}
ex:EmployeeShape {
&ex:PersonShape ;
ex:employeeNumber .
}
This triple expression reference is invalid because there is no corresponding triple expression:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/S1",
"type":"Shape", "expression":
"http://schema.example/missingTripleExpr"
} ] }
S1 {
&missingTripleExpr
}
This triple expression reference is invalid because the referenced object is a shape expression instead of a triple expression:
{ "type":"Schema", "shapes": [
{ "id": "http://schema.example/CustomerShape",
"type":"ShapeAnd", "shapeExprs": [ … ]
},
{ "id": "http://schema.example/PreferredCustomerShape",
"type":"Shape", "expression": { "type":"EachOf", "expressions": [
"http://schema.example/CustomerShape",
{ "type": "TripleConstraint",
"predicate": "http://schema.example/discount" }
] } } ] }
ex:CustomerShape {
…; …
}
ex:PreferredCustomerShape {
&ex:CustomerShape ;
ex:discount .
}
A schema MUST NOT contain any shapeExpr SE which has a shape which contains a TripleConstraint with negated references, either directly or transitively, to SE.
The closure of a shapeExpr SE includes every shape S that appears directly or by shapeExprRef in
If SE is a shape S, the closure of SE is S.
A shapeExpr SE contains shape S if S appears in the closure of SE.
The closure of a tripleExpr TE includes every TripleConstraint TC that appears directly or by tripleExprRef in
If TE is a TripleConstraint TC, the closure of TE is TC.
A tripleExpr TE contains TripleConstraint TC if TC appears in the closure of TE.
A shapeExpr SE1 refers to a shapeExpr SE2 if
A reference of SE1 to SE2 is negated if S appears under an odd number of negations in shapeExpr. A negated reference is one of the following:
a shapeExprRef in a tripleExpr under a ShapeNot
This negated self-reference violates the negation requirement:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#S",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": { "type": "ShapeNot",
"shapeExpr": "http://schema.example/#S" } } }
] }
ex:S {ex:p NOT @ex:S}
This negated, indirect self-reference violates the negation requirement:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#S",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": { "type": "ShapeNot",
"shapeExpr": "http://schema.example/#T"
} } },
{ "id": "http://schema.example/#T",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#q",
"valueExpr": "http://schema.example/#S" } }
] }
ex:S {ex:p NOT @ex:T}
ex:T {ex:q @ex:S}
This is a direct negated self-reference of ex:T and violates the negation requirement:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#T",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": "http://schema.example/#S" } },
{ "id": "http://schema.example/#S",
"type": "ShapeNot",
"shapeExpr": "http://schema.example/#T" },
{ "id": "http://schema.example/#U",
"type": "Shape" }
] }
ex:T {ex:p @ex:S}
ex:S NOT @ex:T AND @ex:U
ex:U .
This doubly-negated self-reference of ex:T does not violate the negation requirement:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#T",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": "http://schema.example/#S" } },
{ "id": "http://schema.example/#S"
"type": "ShapeNot",
"shapeExpr": { "type": "ShapeNot",
"shapeExpr": "http://schema.example/#T" } },
{ "id": "http://schema.example/#U",
"type": "Shape" }
] }
ex:T {ex:p @ex:S}
ex:S NOT (NOT @ex:T AND @ex:U)
ex:U .
This is a negated self-reference of ex:T (indirectly through ex:U) and violates the negation requirement. More precisely, ex:T refers to the negation of ex:U through NOT @ex:S, and ex:U refers to the negation of ex:T trough ex:S.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#T",
"type": "Shape",
"expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": { "type": "ShapeNot",
"shapeExpr": "http://schema.example/#S" } } },
{ "id": "http://schema.example/#U",
"type": "Shape",
"expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/#q",
"valueExpr": "http://schema.example/#S" } },
{ "id": "http://schema.example/#S",
"type": "ShapeNot",
"shapeExpr": "http://schema.example/#T" }
] }
ex:T {ex:p NOT @ex:S}
ex:U {ex:q @ex:S}
ex:S NOT @ex:T AND @ex:U
This satisfies the negation requirement, as ex:U does not refer to ex:T (compared to the previous example).
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#T",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": { "type": "ShapeNot",
"shapeExpr": "http://schema.example/#S" } } },
{ "id": "http://schema.example/#U",
"type": "Shape",
"expression": { "type": "TripleConstraint",
"predicate": "http://schema.example/#q" } },
{ "id": "http://schema.example/#S",
"type": "ShapeNot",
"shapeExpr": "http://schema.example/#T" }
] }
ex:T {ex:p NOT @ex:S}
ex:U {ex:q .}
ex:S NOT @ex:T AND @ex:U
This self-reference on a predicate designated as extra violates the negation requirement:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#S":
"type": "Shape",
"extra": [ "http://schema.example/#p" ], "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": "http://schema.example/#S"
} } ] }
ex:S EXTRA ex:p {
ex:p @ex:S
}
The same shape with a negated self-reference still violates the negation requirement because the reference occurs with a ShapeNot:
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/#S",
"type": "Shape",
"extra": [ "http://schema.example/#p" ],
"expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/#p",
"valueExpr": {
"type": "ShapeNot", "shapeExpr": "http://schema.example/#S"
} } } ] }
ex:S EXTRA ex:p {
ex:p NOT @ex:S
}
Semantic actions serve as an extension point for Shape Expressions. They appear in lists in Schema's startActs and Shape, OneOf, EachOf and TripleConstraint's semActs.
A semantic action is a tuple of an identifier and some optional code:
The evaluation semActsSatisfied on a list of SemActs returns success or failure. The evaluation of an individual SemAct is implementation-dependent.
A practical evaluation of a SemAct will provide access to some context.
For instance, the http://shex.io/extensions/Test/ extension requires access to the subject, predicate and object of a triple matching a TripleConstraint.
These are used in a print function.
{ "type": "Schema", "shapes": [
{ "id": "http://a.example/S1",
"type": "Shape", "expression": {
"type": "TripleConstraint", "predicate": "http://a.example/p1",
"min": 1, "max": -1,
"semActs": [
{ "type": "SemAct", "code": " print(s) ",
"name": "http://shex.io/extensions/Test/" },
{ "type": "SemAct", "code": " print(o) ",
"name": "http://shex.io/extensions/Test/" } ] } } ] }
ex:S1 {
ex:p1 .+ %Test:{ print(s) %} %Test:{ print(o) %}
}
<http://a.example/n1> <http://a.example/p1> <http://a.example/o1> . <http://a.example/n2> <http://a.example/p1> "a", "b" . <http://a.example/n3> <http://a.example/p2> <http://a.example/o2> .
| shape | node | result | print arguments |
|---|---|---|---|
| <S1> | <n1> | pass | http://a.example/s1 http://a.example/o1 |
| <S1> | <n2> | pass | http://a.example/s1 "a" http://a.example/s1 "b" |
| <S1> | <n3> | fail |
Annotations provide a format-independent way to provide additional information about elements in a schema. They appear in lists in Shape, OneOf, EachOf and TripleConstraint's annotations.
| Annotation | { | predicate:IRI object:objectValue } |
|---|
Annotations do not affect whether a node conforms to some shape. Because they are part of the structure of the schema, they can be parsed in one ShEx format and emitted in that format or another.
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression": {
"type": "TripleConstraint",
"predicate": "http://schema.example/status",
"annotations": [
{ "type": "Annotation",
"predicate": "http://www.w3.org/2000/01/rdf-schema#comment",
"object": {"value": "Represents reported software issues."} },
{ "type": "Annotation",
"predicate": "http://www.w3.org/2000/01/rdf-schema#label",
"object": {"value": "software issue"} } ] } } ] }
ex:IssueShape {
ex:status .
// rdfs:comment "Represents reported software issues."
// rdfs:label "software issue"
}
The following examples demonstrate proofs for validations in the form of a nested list of invocations of the evaluation functions defined above.
S1 nc1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IntConstraint",
"type": "NodeConstraint",
"datatype": "http://www.w3.org/2001/XMLSchema#integer"
} ] }
ex:IntConstraint
xsd:integer
Here the shape identified by http://schema.example/IntConstraint is a shape expression consisting of a single NodeConstraint.
Per Shape Expression Semantics, "30"^^<http://www.w3.org/2001/XMLSchema#integer> satisfies IntConstraint.
This document uses this nested tree convention to indicate that the dependency of an evaluation on those nested inside it. Nesting is expressed as indentation. Here, the evaluation of satisfies NodeConstraint ("30"^^xsd:integer, S1, G, m) depends on satisfies2 NodeConstraint ("30"^^xsd:integer, S1).
Validating a shape requires evaluating it's triple expression as well as the variables and functions neigh(G, n), matched, remainder, outs, matchables and unmatchables:
S1 tc1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/UserShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/shoeSize"
} } ] }
ex:UserShape {
ex:shoeSize .
}
t1
BASE <http://a.example/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> <Alice> ex:shoeSize "30"^^xsd:integer .
It is quite common that Shapes will constrain their nested TripleConstraints with NodeConstraints. Here is an example including that, extra triples and a closed shape:
S1 tc1 nc1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/UserShape",
"type": "Shape", "expression":
"extra": ["http://www.w3.org/1999/02/22-rdf-syntax-ns#type"],
{ "type": "TripleConstraint",
"predicate": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type",
"valueExpr":
{ "type": "NodeConstraint",
"values": ["http://schema.example/Teacher"]
} } } ] }
ex:UserShape EXTRA a {
a
[ex:Teacher]
}
t1 t2 t3 t4 t5
BASE <http://a.example/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> <Alice> ex:shoeSize "30"^^xsd:integer . <Alice> a ex:Teacher . <Alice> a ex:Person . <SomeHat> ex:owner <Alice> . <TheMoon> ex:madeOf <GreenCheese> .
The non-empty matchables is permitted because the triple t3 has a predicate which appears in the "extra" list: ["http://schema.example/Teacher"].
S1 te1 tc1 nc1 te2 tc2 nc2 tc3 nc3
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/UserShape",
"type": "Shape", "expression":
{"type": "OneOf", "expressions": [
{ "type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/name",
"valueExpr":
{ "type": "NodeConstraint", "nodeKind": "literal" } },
{ "type": "EachOf", "expressions": [
{ "type": "TripleConstraint", "min": 1, "max": -1 ,
"predicate": "http://xmlns.com/foaf/0.1/givenName",
"valueExpr":
{ "type": "NodeConstraint", "nodeKind": "literal" } },
{ "type": "TripleConstraint",
"predicate": "http://xmlns.com/foaf/0.1/familyName",
"valueExpr":
{ "type": "NodeConstraint", "nodeKind": "literal" } }
] }
] }
} ] }
ex:UserShape
{
( # extra ()s to clarify alignment with ShExJ
foaf:name
LITERAL |
( # extra ()s to clarify alignment with ShExJ
foaf:givenName
LITERAL+ ;
foaf:familyName
LITERAL
)
)
}
t1 t2 t3 t4 t5 t6
BASE <http://a.example/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> <Alice> foaf:givenName "Alice" . <Alice> foaf:givenName "Malsenior" . <Alice> foaf:familyName "Walker" . <Alice> foaf:mbox <mailto:alice@example.com> . <Bob> foaf:knows <Alice> . <Bob> foaf:mbox <mailto:bob@example.com> .
Per Shape Expression Semantics, <Alice> satisfies S1 with the simple ShapeMap
m:
{ "http://a.example/Alice": "http://a.example/UserShape }
as seen in this validation.
Replacing triples 1-3 with a single foaf:name property will also satisfy the schema.
t4 t5 t6 t7
BASE <http://a.example/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> <Alice> foaf:mbox <mailto:alice@example.com> . <Bob> foaf:knows <Alice> . <Bob> foaf:mbox <mailto:bob@example.com> . <Alice> foaf:name "Alice Malsenior Walker" .
Any mixure of foaf:name with foaf:givenName or foaf:familyName will fail to satisfy the schema as there will be a matchable triple t3 that's not used in the triple expression te1.
t3 t4 t5 t6 t7
BASE <http://a.example/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
<Alice> foaf:familyName "Walker" .
<Alice> foaf:mbox <mailto:alice@example.com> .
<Bob> foaf:knows <Alice> .
<Bob> foaf:mbox <mailto:bob@example.com> .
<Alice> foaf:name "Alice Malsenior Walker" .
Adding a foaf:familyName to S1's extra would allow this graph to satisfy the schema.
S1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/UserShape",
"type": "Shape", "extra": ["http://xmlns.com/foaf/0.1/familyName"] …
} ] }
Closing S1 would also cause a validation failure if unmatchables were not empty:
S1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/UserShape",
"type": "Shape", "closed": true …
} ] }
S1 tc1 nc1 S2 tc2 nc2
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/reproducedBy",
"valueExpr":
"http://schema.example/TesterShape" } },
{ "id": "http://schema.example/TesterShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/role",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ "http://schema.example/testingRole" ] } } }
] }
ex:IssueShape
{
ex:reproducedBy
@ex:TesterShape }
ex:TesterShape
{
ex:role
[ex:testingRole] }
t1 t2
PREFIX ex: <http://schema.example/> PREFIX inst: <http://inst.example/> inst:Issue1 ex:reproducedBy inst:Tester2 . inst:Tester2 ex:role ex:testingRole .
inst:Issue1 satisfies S1 with the ShapeMap
m:
{ "http://inst.example/Issue1": "http://schema.example/IssueShape",
"http://inst.example/Tester2": "http://schema.example/TesterShape",
"http://inst.example/Testgrammer23": "http://schema.example/ProgrammerShape" }
as seen in this evaluation:
S1 tc1 nc1
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint", "min": 0, "max": -1,
"predicate": "http://schema.example/related",
"valueExpr":
"http://schema.example/IssueShape"
} } ] }
ex:IssueShape {
ex:related
@ex:IssueShape*
}
t1 t2 t3
PREFIX ex: <http://schema.example/> PREFIX inst: <http://inst.example/> inst:Issue1 ex:related inst:Issue2 . inst:Issue2 ex:related inst:Issue3 . inst:Issue3 ex:related inst:Issue1 .
inst:Issue1 satisfies S1 with the ShapeMap
m:
{ "http://inst.example/Issue1": "http://schema.example/IssueShape",
"http://inst.example/Issue2": "http://schema.example/IssueShape",
"http://inst.example/Issue3": "http://schema.example/IssueShape" }
as seen in this evaluation:
S1 te1 tc1 nc1 tc2 nc2
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/TestResultsShape",
"type": "Shape", "expression": {
"type": "EachOf", "expressions": [
{ "type": "TripleConstraint", "min": 1, "max": -1,
"predicate": "http://schema.example/val",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ {"value": "a"}, {"value": "b"}, {"value": "c"} ] } },
{ "type": "TripleConstraint", "min": 1, "max": -1,
"predicate": "http://schema.example/val",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ {"value": "b"}, {"value": "c"}, {"value": "d"} ] } }
] } } ] }
<http://schema.example/TestResultsShape>
{
<http://schema.example/val>
["a" "b" "c"]+ ;
<http://schema.example/val>
["b" "c" "d"]+
}
t1 t2 t3 t4
BASE <http://a.example/> PREFIX ex: <http://schema.example/> <s> ex:val "a" . <s> ex:val "b" . <s> ex:val "c" . <s> ex:val "d" .
<s> satisfies S1 with:
m:
{ "http://a.example/s": "http://a.example/S1 }
If tc1 consumes as many triples as it can, it consumes three and tc2 consumes one:
If we eliminate t4, either t2 or t3 must be allocated to tc2:
S1 te1 tc1 nc1 tc2 nc2 S2 tc3 nc3 S3 tc4 nc4
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/IssueShape",
"type": "Shape", "expression":
{ "type": "EachOf", "expressions": [
{ "type": "TripleConstraint",
"predicate": "http://schema.example/reproducedBy",
"valueExpr":
"http://schema.example/TesterShape" },
{ "type": "TripleConstraint",
"predicate": "http://schema.example/reproducedBy",
"valueExpr":
"http://schema.example/ProgrammerShape" }
] } },
{ "id": "http://schema.example/TesterShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/role",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ "http://schema.example/testingRole" ] } } },
{ "id": "http://schema.example/ProgrammerShape",
"type": "Shape", "expression":
{ "type": "TripleConstraint",
"predicate": "http://schema.example/department",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ "http://schema.example/ProgrammingDepartment" ] } } }
] }
ex:IssueShape {
ex:reproducedBy
@ex:TesterShape;
ex:reproducedBy
@ex:ProgrammerShape
}
ex:TesterShape {
ex:role
[ex:testingRole]
}
ex:ProgrammerShape {
ex:department
[ex:ProgrammingDepartment]
}
t1 t2 t3 t4 t5
PREFIX ex: <http://schema.example/> PREFIX inst: <http://inst.example/> inst:Issue1 ex:reproducedBy inst:Tester2 ; ex:reproducedBy inst:Testgrammer23 . inst:Tester2 ex:role ex:testingRole . inst:Testgrammer23 ex:role ex:testingRole ; ex:department ex:ProgrammingDepartment .
inst:Issue1 satisfies S1 with the ShapeMap
m:
{ "http://inst.example/Issue1": "http://schema.example/IssueShape",
"http://inst.example/Tester2": "http://schema.example/TesterShape",
"http://inst.example/Testgrammer23": "http://schema.example/ProgrammerShape" }
as seen in this evaluation:
Setting the maximum cardinality of a TripleConstraint with predicate p to zero (i.e. "max": 0 in ShExJ or {0} or {0, 0} in ShExC) asserts that matching nodes must have no triples with predicate p.
S1 te1 tc1 nc1 tc2
{ "type": "Schema", "shapes": [
{ "id": "http://schema.example/TestResultsShape",
"type": "Shape", "expression": {
"type": "EachOf", "expressions": [
{ "type": "TripleConstraint", "min": 1, "max": -1,
"predicate": "http://schema.example/p1",
"valueExpr":
{ "type": "NodeConstraint",
"values": [ {"value": "a"}, {"value": "b"} ] } },
{ "type": "TripleConstraint", "min": 1, "max": -1,
"predicate": "http://schema.example/p2", "min": 0, "max": 0 }
] } } ] }
<http://schema.example/TestResultsShape>
{
<http://schema.example/p1>
["a" "b"] ;
<http://schema.example/p2> . {0}
}
t1
BASE <http://a.example/> PREFIX ex: <http://schema.example/> <s> ex:p1 "a" .
<s> satisfies S1 with:
m:
{ "http://a.example/s": "http://a.example/S1" }
If tc1 consumes as many triples as it can, it consumes three and tc2 consumes one:
If we add a t2 which matches tc2:
t1 t2
BASE <http://a.example/> PREFIX ex: <http://schema.example/> <s> ex:p1 "a" . <s> ex:p2 5 .
every partition fails, either because matchables is non-empty or because the maximum cardinality on tc2 is exceeded:
The ShEx Compact Syntax expresses ShEx schemas in a compact, human-friendly form.
Parsing ShExC transforms a ShExC document into an equivalent ShExJ structure.
This is defined as a BNF which accepts ShExC followed by instructions for tranlating the rules in the BNF production into their corresponding ShExJ objects.
For example, "shapeExprDecl returns shapeExpression" indicates that the result of matching the shapeExprDecl production is the object produced by parsing the shapeExpression production.
Semantic actions before the first shape expression declaration are startActs. After the first shape expression declaration, semantic actions are associated with the previous declaration.
| Below is the ShExC grammar following the notation in the XML specification[[!XML]]: | |||
| [1] | shexDoc |
::= | directive* ((notStartAction | startActions) statement*)? |
| followed by the associated ShExJ object(s): | |||
| Schema | { | startActs:[SemAct]? start:shapeExpr? shapes:[shapeExpr+]? } | |
| SemAct | { | name:IRI code:STRING? } | |
| and a description of the mapping of rules in the production to elements of the ShExJ object: | |||
| |||
| [2] | directive |
::= | baseDecl | prefixDecl |
| [3] | baseDecl |
::= | "BASE" IRIREF |
| [4] | prefixDecl |
::= | "PREFIX" PNAME_NS IRIREF |
| [5] | notStartAction |
::= | start | shapeExprDecl |
| [6] | start |
::= | "start" '=' inlineShapeExpression |
| [7] | startActions |
::= | codeDecl+ |
| [8] | statement |
::= | directive | notStartAction |
| [9] | shapeExprDecl |
::= | shapeExprLabel (shapeExpression | "EXTERNAL") |
If the "EXTERNAL" keyword is present, shapeExprDecl returns a ShapeExternal object: | |||
| ShapeExternal | { | id:shapeExprLabel? } | |
| otherwise shapeExprDecl returns shapeExpression. | |||
|
Shape expressions are logical combinations of shape atoms. Inline variants of shape expressions are used in tripleConstraints and are not permitted to have annotations or semantic actions. | |||
| [10] | shapeExpression |
::= | "NOT"? shapeAtomNoRef shapeOr? |
| [11] | inlineShapeExpression |
::= | inlineShapeOr |
| [12] | shapeOr |
::= | ("OR" shapeAnd)+ |
| [13] | inlineShapeOr |
::= | inlineShapeAnd ("OR" inlineShapeAnd)* |
| If the right shapeAnd matches one or more times, the result is a ShapeOr object with shapeExprs containing the first shapeAnd followed by the ordered list from the second shapeAnd: | |||
| ShapeOr | { | id:shapeExprLabel? shapeExprs:[shapeExpr] } | |
| otherwise the result is the left shapeAnd. | |||
| [14] | shapeAnd |
::= | shapeNot ("AND" shapeNot)* |
| [15] | inlineShapeAnd |
::= | inlineShapeNot ("AND" inlineShapeNot)* |
| If the right shapeNot matches one or more times, the result is a ShapeAnd object with shapeExprs containing the first shapeNot followed by the ordered list from the second shapeNot: | |||
| ShapeAnd | { | id:shapeExprLabel? shapeExprs:[shapeExpr] } | |
| otherwise the result is the left shapeNot. | |||
| [16] | shapeNot |
::= | "NOT"? shapeAtom |
| [17] | inlineShapeNot |
::= | "NOT"? inlineShapeAtom |
If the left "NOT" matches, the result is a ShapeNot object with shapeExpr containing the shapeAtom: | |||
| ShapeNot | { | id:shapeExprLabel? shapeExpr:shapeExpr } | |
| otherwise the result is the shapeAtom. | |||
|
Shape atoms are shape references (indicated by " | |||
| [18] | shapeAtom |
::= | nonLitNodeConstraint shapeOrRef? |
| [19] | shapeAtomNoRef |
::= | nonLitNodeConstraint shapeOrRef? |
| [20] | inlineShapeAtom |
::= | nonLitNodeConstraint inlineShapeOrRef? |
| |||
| [21] | shapeOrRef |
::= | shapeDefinition | shapeRef
|
| [22] | inlineShapeOrRef |
::= | inlineShapeDefinition | shapeRef
|
| [23] | shapeRef |
::= | ATPNAME_LN | ATPNAME_NS | '@' shapeExprLabel |
| |||
| shapeExprRef | = | shapeExprLabel ; | |
|
Node constraints identify a (possibly infinite) set of matching RDF nodes. | |||
| [24] | litNodeConstraint |
::= | "LITERAL" xsFacet* |
| [25] | nonLitNodeConstraint |
::= | nonLiteralKind stringFacet* |
| NodeConstraint | { | nodeKind:("iri" | "bnode" | "nonliteral" | "literal")? datatype:IRI? xsFacet* values:[valueSetValue]? } | |
| [26] | nonLiteralKind |
::= | "IRI" | "BNODE" | "NONLITERAL" |
| [27] | xsFacet |
::= | stringFacet | numericFacet |
| xsFacet | = | stringFacet | numericFacet ; | |
| [28] | stringFacet |
::= | stringLength INTEGER |
| [29] | stringLength |
::= | "LENGTH" | "MINLENGTH" | "MAXLENGTH" |
| stringFacet | = | ("length"|"minlength"|"maxlength"):INTEGER | pattern:STRING flags:STRING? ; | |
| [30] | numericFacet |
::= | numericRange numericLiteral |
| [31] | numericRange |
::= | "MININCLUSIVE" | "MINEXCLUSIVE" | "MAXINCLUSIVE" | "MAXEXCLUSIVE" |
| [32] | numericLength |
::= | "TOTALDIGITS" | "FRACTIONDIGITS" |
| numericFacet | { | ("mininclusive"|"minexclusive"|"maxinclusive"|"maxexclusive"):numericLiteral | ("totaldigits"|"fractiondigits"):INTEGER ; | |
|
Shape defintions associate a triple expression with a closed flag and a list of partially constrained (extra) predicates. Any predicate appearing in a triple expression is fully constrained unless it appears in the list of extras. | |||
| [33] | shapeDefinition |
::= | (extraPropertySet | "CLOSED")* '{' tripleExpression? '}' annotation* semanticActions |
| [34] | inlineShapeDefinition |
::= | (extraPropertySet | "CLOSED")* '{' tripleExpression? '}' |
| Shape | { | closed:BOOL? extra:[IRI]? expression:tripleExpr? annotations:[Annotation]? semActs:[SemAct]? } | |
| Annotation | { | predicate:IRI object:objectValue } | |
| |||
| [35] | extraPropertySet |
::= | "EXTRA" predicate+ |
|
Triple expressions are arrangements of triple constraints. | |||
| [36] | tripleExpression |
::= | oneOfTripleExpr |
| [37] | oneOfTripleExpr |
::= | groupTripleExpr | multiElementOneOf |
| [38] | multiElementOneOf |
::= | groupTripleExpr ('|' groupTripleExpr)+ |
| If the right groupTripleExpr matches one or more times, the result is a OneOf object with expressions containing the first groupTripleExpr followed by the ordered list from the second groupTripleExpr: | |||
| OneOf | { | id:tripleExprLabel? expressions:[tripleExpr] min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } | |
| otherwise the result is the left groupTripleExpr. | |||
| [39] | innerTripleExpr |
::= | multiElementGroup | multiElementOneOf |
| [40] | groupTripleExpr |
::= | singleElementGroup | multiElementGroup |
| [41] | singleElementGroup |
::= | unaryTripleExpr ';'? |
| [42] | multiElementGroup |
::= | unaryTripleExpr (';' unaryTripleExpr)+ ';'? |
| If the right unaryTripleExpr matches one or more times, the result is a EachOf object with expressions containing the first unaryTripleExpr followed by the ordered list from the second unaryTripleExpr: | |||
| EachOf | { | id:tripleExprLabel? expressions:[tripleExpr] min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } | |
| otherwise the result is the left unaryTripleExpr. | |||
| [43] | unaryTripleExpr |
::= | ('$' tripleExprLabel)? (tripleConstraint | bracketedTripleExpr) |
| [44] | bracketedTripleExpr |
::= | '(' innerTripleExpr ')' cardinality? annotation* semanticActions |
|
Triple constraints are matched against RDF triples. | |||
| [45] | tripleConstraint |
::= | senseFlags? predicate inlineShapeExpression cardinality? annotation* semanticActions |
| TripleConstraint | { | inverse:BOOL? predicate:IRI valueExpr:shapeExpr? min:INTEGER? max:INTEGER? semActs:[SemAct]? annotations:[Annotation]? } | |
| |||
| [46] | cardinality |
::= | '*' | '+' | '?' | REPEAT_RANGE |
In ShExJ, "*" is represented as -1, standing for the unbounded cardinality..
| |||
| [47] | senseFlags |
::= | '^' |
|
Value sets identify ranges of RDF nodes by explicit inclusion or by range (indicated by " | |||
| [48] | valueSet |
::= | '[' valueSetValue* ']' |
| [49] | valueSetValue |
::= | iriRange | literalRange | languageRange |
If "." matches and exclusion matches one or more times, all matched items must be consistently iri, literal, or language. valueSetValue returns either a IriStemRange, LiteralStemRange, or LanguageStemRange object with exclusions equal to the set of results of exclusion: | |||
| IriStemRange | { | stem:(IRI | Wildcard) exclusions:[valueSetValue]? } | |
| LiteralStemRange | { | stem:(LITERAL | Wildcard) exclusions:[valueSetValue]? } | |
| LanguageStemRange | { | stem:(language tag | Wildcard) exclusions:[valueSetValue]? } | |
If "~" matches with no exclusion, valueSetValue returns a Wildcard object: | |||
| Wildcard | { | /* contains no properties */ } | |
| [50] | exclusion |
::= | '-' (iri | literal | LANGTAG) '~'? |
| [51] | iriRange |
::= | iri ('~' exclusion*)? |
If iri matches with no "~", iriRange returns iri. | |||
If iri and "~" match with no iriExclusion, iriRange returns a IriStem object: | |||
| IriStem | { | stem:IRI } | |
If iri and "~" match and iriExclusion matches one or more times, iriRange returns a IriStemRange object with exclusions equal to the set of results of iriExclusion: | |||
| [52] | iriExclusion |
::= | '-' iri '~'? |
| [53] | literalRange |
::= | literal ('~' literalExclusion*)? |
If literal matches with no "~", literalRange returns literal. | |||
If literal and "~" match with no literalExclusion, literalRange returns a LiteralStem object: | |||
| LiteralStem | { | stem:objectLiteral } | |
If literal and "~" match and literalExclusion matches one or more times, literalRange returns a LiteralStemRange object with exclusions equal to the set of results of literalExclusion: | |||
| [54] | literalExclusion |
::= | '-' literal '~'? |
| [55] | languageRange |
::= | LANGTAG ('~' languageExclusion*)? |
If LANGTAG matches with no "~", languageRange returns LANGTAG. | |||
If LANGTAG and "~" match with no languageExclusion, languageRange returns a LanguageStem object: | |||
| LanguageStem | { | stem:objectLiteral } | |
If LANGTAG and "~" match and languageExclusion matches one or more times, languageRange returns a LanguageStemRange object with exclusions equal to the set of results of languageExclusion: | |||
| [56] | languageExclusion |
::= | '-' LANGTAG '~'? |
|
Triple expressions can include the shapeExpression in a shapeExprDecl. | |||
| [57] | include |
::= | '&' tripleExprLabel |
| Per the triple expression refrence requirement, tripleExprLabel property MUST appear in the schema's shapes map and the corresponding triple expression MUST be a Shape with a tripleExpr. | |||
| tripleExprRef | = | include:tripleExprLabel ; | |
|
Triple expressions can include annotations in the form of a tuple of a predicate and an iri or literal. | |||
| [58] | annotation |
::= | "//" predicate (iri | literal) |
| Annotation | { | predicate:IRI object:objectValue } | |
|
Triple expressions can include semantic actions consisting of an iri and an optional code string. | |||
| [59] | semanticActions |
::= | codeDecl* |
| [60] | codeDecl |
::= | '%' iri (CODE | '%') |
| SemAct | { | name:IRI code:STRING? } | |
|
The remaining productions come from the specifications for SPARQL and Turtle. | |||
| [13t] | literal |
::= | rdfLiteral | numericLiteral | booleanLiteral |
| [61] | predicate |
::= | iri | RDF_TYPE |
| [62] | datatype |
::= | iri |
| [63] | shapeExprLabel |
::= | iri | blankNode |
| [64] | tripleExprLabel |
::= | iri | blankNode |
| [16t] | numericLiteral |
::= | INTEGER | DECIMAL | DOUBLE |
| [65] | rdfLiteral |
::= | langString | string ("^^" datatype)? |
| returns: literal | The literal has a lexical form of the first rule argument, String. If the '^^' iri rule matched, the datatype is iri and the literal has no language tag. If the langString rule matched, the datatype is rdf:langString and the language tag is extracted from langTag. If neither matched, the datatype is xsd:string and the literal has no language tag. | ||
| [134s] | booleanLiteral |
::= | "true" | "false" |
| returns: literal | The literal has a lexical form of the true or false, depending on which matched the input, and a datatype of xsd:boolean. | ||
| [135s] | string |
::= | STRING_LITERAL1 | STRING_LITERAL_LONG1 |
| [66] | langString |
::= | LANG_STRING_LITERAL1 | LANG_STRING_LITERAL_LONG1 |
| [136s] | iri |
::= | IRIREF | prefixedName |
| [137s] | prefixedName |
::= | PNAME_LN | PNAME_NS |
| [138s] | blankNode |
::= | BLANK_NODE_LABEL |
TerminalsTerminals return:
| |||
| [67] | <CODE> |
::= | "{" ([^%\\] | "\\" [%\\] | UCHAR)* "%" "}" |
| returns: a string of unicode codepoints | The characters between "{" and "%}" are taken, with the numeric escape sequences unescaped, to form the unicode string of the IRI. | ||
| [68] | <REPEAT_RANGE> |
::= | "{" INTEGER ( "," (INTEGER | "*")? )? "}" |
| returns: repeat range | The base-10 numeric values of INTEGER are taken or a non-negative integer and an * token if "*" was matched. | ||
| [69] | <RDF_TYPE> |
::= | "a" |
| returns: IRI | The iri http://www.w3.org/1999/02/22-rdf-syntax-ns# is returned. | ||
| [18t] | <IRIREF> |
::= | "<" ([^#0000- <>\"{}|^`\\] | UCHAR)* ">" |
| returns: IRI | The characters between "<" and ">" are taken, with the numeric escape sequences unescaped, to form the unicode string of the IRI. Relative IRI resolution is performed per Turtle Section 6.3. | ||
| [140s] | <PNAME_NS> |
::= | PN_PREFIX? ":" |
| returns: PREFIX | When used in a prefixDecl production, the prefix is a potentially empty unicode string matching the first argument of the rule and serves as a key into the prefixes map. | ||
| returns: IRI | When used elsewhere, the iri is the value in the prefixes map corresponding to the first argument of the rule. | ||
| [141s] | <PNAME_LN> |
::= | PNAME_NS PN_LOCAL |
| returns: IRI | A potentially empty prefix is identified by the first token, PNAME_NS. The prefixes map MUST have a corresponding namespace. The unicode string of the IRI is formed by unescaping the reserved characters in the second argument, PN_LOCAL, and concatenating this onto the namespace. | ||
| [70] | <ATPNAME_NS> |
::= | "@" PNAME_NS |
| returns: IRI | The iri is the value in the prefixes map corresponding to the second token of the rule. | ||
| [71] | <ATPNAME_LN> |
::= | "@" PNAME_LN |
| returns: IRI | A potentially empty prefix is identified by the second token, PNAME_NS. The prefixes map MUST have a corresponding namespace. The unicode string of the IRI is formed by unescaping the reserved characters in the third token, PN_LOCAL, and concatenating this onto the namespace. | ||
| [72] | <REGEXP> |
::= | '/' ([^/\\\n\r] | '\\' [nrt\\|.?*+(){}$-\[\]^/] | UCHAR)+ '/' [smix]* |
| { | pattern:STRING flags:STRING? } | ||
| returns: JSON object | pattern is a unicode string formed from the characters between the outermost '/'s by unescaping matches of '\\' '/' in the terminal pattern as well as the numeric escape sequences matched by UCHAR.
The remaining escape sequences are included verbatim in pattern, e.g. ^\/\t\\\U0001D4B8$ ^/\t\\\U0001D4B8$ flags is a sequence of the characters [smix] if any were matched. Otherwise no flags attribute is returned. | ||
| [142s] | <BLANK_NODE_LABEL> |
::= | "_:" (PN_CHARS_U | [0-9]) ((PN_CHARS | ".")* PN_CHARS)? |
| returns: BNode | The characters following the "_:" form a blank node identifier. This corresponds to any blank node in the input dataset that had the same label. | ||
| [145s] | <LANGTAG> |
::= | "@" ([a-zA-Z])+ ("-" ([a-zA-Z0-9])+)* |
| returns: language tag | The characters following the @ form the unicode string of the language tag. | ||
| [19t] | <INTEGER> |
::= | [+-]? [0-9]+ |
| returns: literal | The literal has a lexical form of the input string, and a datatype of xsd:integer. | ||
| [20t] | <DECIMAL> |
::= | [+-]? [0-9]* "." [0-9]+ |
| returns: literal | The literal has a lexical form of the input string, and a datatype of xsd:double. | ||
| [21t] | <DOUBLE> |
::= | [+-]? ([0-9]+ "." [0-9]* EXPONENT | "."? [0-9]+ EXPONENT) |
| returns: literal | The literal has a lexical form of the input string, and a datatype of xsd:double. | ||
| [155s] | <EXPONENT> |
::= | [eE] [+-]? [0-9]+ |
| [156s] | <STRING_LITERAL1> |
::= | "'" ([^'\\\n\r] | ECHAR | UCHAR)* "'" |
| returns: lexical form | The characters between the outermost "'"s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. | ||
| [157s] | <STRING_LITERAL2> |
::= | '"' ([^\"\\\n\r] | ECHAR | UCHAR)* '"' |
| returns: lexical form | The characters between the outermost '"'s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. | ||
| [158s] | <STRING_LITERAL_LONG1> |
::= | "'''" ( ("'" | "''")? ([^\\'\\] | ECHAR | UCHAR) )* "'''" |
| returns: lexical form | The characters between the outermost "'''"s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. | ||
| [159s] | <STRING_LITERAL_LONG2> |
::= | '"""' ( ('"' | '""')? ([^\"\\] | ECHAR | UCHAR) )* '"""' |
| returns: lexical form | The characters between the outermost '"""'s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. | ||
| [73] | <LANG_STRING_LITERAL1> |
::= | "'" ([^'\\\n\r] | ECHAR | UCHAR)* "'" LANGTAG |
| returns: lexical form | The characters between the outermost "'"s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. The trailing LANGTAG is used to create a language-tagged string. | ||
| [74] | <LANG_STRING_LITERAL2> |
::= | '"' ([^\"\\\n\r] | ECHAR | UCHAR)* '"' LANGTAG |
| returns: lexical form | The characters between the outermost '"'s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. The trailing LANGTAG is used to create a language-tagged string. | ||
| [75] | <LANG_STRING_LITERAL_LONG1> |
::= | "'''" ( ("'" | "''")? ([^\\'\\] | ECHAR | UCHAR) )* "'''" LANGTAG |
| returns: lexical form | The characters between the outermost "'''"s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. The trailing LANGTAG is used to create a language-tagged string. | ||
| [76] | <LANG_STRING_LITERAL_LONG2> |
::= | '"""' ( ('"' | '""')? ([^\"\\] | ECHAR | UCHAR) )* '"""' LANGTAG |
| returns: lexical form | The characters between the outermost '"""'s are taken, with numeric and string escape sequences unescaped, to form the unicode string of a lexical form. The trailing LANGTAG is used to create a language-tagged string. | ||
| [26t] | <UCHAR> |
::= | "\\u" HEX HEX HEX HEX |
| [160s] | <ECHAR> |
::= | "\\" [tbnrf\\\"\\'] |
| [164s] | <PN_CHARS_BASE> |
::= | [A-Z] | [a-z] |
| [165s] | <PN_CHARS_U> |
::= | PN_CHARS_BASE | "_" |
| [167s] | <PN_CHARS> |
::= | PN_CHARS_U | "-" | [0-9] |
| [168s] | <PN_PREFIX> |
::= | PN_CHARS_BASE ( (PN_CHARS | ".")* PN_CHARS )? |
| [169s] | <PN_LOCAL> |
::= | (PN_CHARS_U | ":" | [0-9] | PLX) ( (PN_CHARS | "." | ":" | PLX)* (PN_CHARS | ":" | PLX) )? |
| [170s] | <PLX> |
::= | PERCENT | PN_LOCAL_ESC |
| [171s] | <PERCENT> |
::= | "%" HEX HEX |
| [172s] | <HEX> |
::= | [0-9] | [A-F] | [a-f] |
| [173s] | <PN_LOCAL_ESC> |
::= | "\\" ( "_" | "~" | "." | "-" | "!" | "$" | "&" | "'" | "(" | ")" | "*" | "+" | "," | ";" | "=" | "/" | "?" | "#" | "@" | "%" ) |
| [98] | PASSED TOKENS |
::= | [ \t\r\n]+ |
This section defines a set of properties and permitted values for describing Shape Expressions in JSON [[!RFC7159]], and how these properties should be interpreted by applications.
A ShExJ document is a JSON-LD [[!JSON-LD]] document uses
a proscribed structure which holds an object at the top level. This object describes a schema containing
shape expressions and triple expressions. A ShExJ document
MUST include a @context property referencing http://www.w3.org/ns/shex.jsonld, and MAY include additional contexts
and term definitions. In the absense of a top-level @context, ShEx Processors MUST act as if a @context property is present with the value http://www.w3.org/ns/shex.jsonld.
A ShExJ document can also be thought of as the serialization of an RDF Graph using the Shape Expression Vocabulary [[shex-vocab]] which conforms to the shape defined in . Processors MAY choose to interpret a ShExJ document as an RDF Graph and process using RDF Graph semantics. Processors may also transform arbitrary RDF Graphs conforming to into ShExJ using a mechanism not described within this specification.
In ShExJ, the unbounded cardinality constraint is -1, rather than "*".
This is the complete grammar for ShExJ.
| Schema | { | "@context": "http://www.w3.org/ns/shex.jsonld" startActs:[SemAct+]? start:shapeExpr? shapes:[shapeExpr+]? } |
|---|---|---|
| shapeExpr | = | ShapeOr | ShapeAnd | ShapeNot | NodeConstraint | Shape | shapeExprRef | ShapeExternal ; |
| ShapeOr | { | id:shapeExprLabel? shapeExprs:[shapeExpr{2,}] } |
| ShapeAnd | { | id:shapeExprLabel? shapeExprs:[shapeExpr{2,}] } |
| ShapeNot | { | id:shapeExprLabel? shapeExpr:shapeExpr } |
| NodeConstraint | { | id:shapeExprLabel? nodeKind:("iri" | "bnode" | "nonliteral" | "literal")? datatype:IRI? xsFacet* values:[valueSetValue+]? } |
| Shape | { | id:shapeExprLabel? closed:BOOL? extra:[IRI+]? expression:tripleExpr? semActs:[SemAct+]? } |
| shapeExprRef | = | shapeExprLabel ; |
| ShapeExternal | { | /* empty */ } |
| tripleExpr | = | EachOf | OneOf | TripleConstraint | tripleExprRef ; |
| EachOf | { | id:tripleExprLabel? expressions:[tripleExpr{2,}] min:INTEGER? max:INTEGER? semActs:[SemAct+]? annotations:[Annotation+]? } |
| OneOf | { | id:tripleExprLabel? expressions:[tripleExpr{2,}] min:INTEGER? max:INTEGER? semActs:[SemAct+]? annotations:[Annotation+]? } |
| tripleExprRef | { | include:shapeExprLabel } |
| TripleConstraint | { | id:tripleExprLabel? inverse:BOOL? predicate:IRI valueExpr:shapeExpr? min:INTEGER? max:INTEGER? semActs:[SemAct+]? annotations:[Annotation+]? } |
| xsFacet | = | stringFacet | numericFacet ; |
| stringFacet | = | ("length"|"minlength"|"maxlength"):INTEGER | pattern:STRING flags:STRING ; |
| numericFacet | = | ("mininclusive"|"minexclusive"|"maxinclusive"|"maxexclusive"):numericLiteral |
| | | ("totaldigits"|"fractiondigits"):INTEGER ; | |
| valueSetValue | = | objectValue | IriStem | IriStemRange | LiteralStem | LiteralStemRange | LanguageStem | LanguageStemRange ; |
| objectValue | = | IRI | ObjectLiteral ; |
| IriStem | { | stem:IRI } |
| IriStemRange | { | stem:(IRI | Wildcard) exclusions:[objectValue|IriStem +]? } |
| LiteralStem | { | stem:ObjectLiteral } |
| LiteralStemRange | { | stem:(ObjectLiteral | Wildcard) exclusions:[objectValue|LiteralStem +]? } |
| LanguageStem | { | stem:ObjectLiteral } |
| LanguageStemRange | { | stem:(ObjectLiteral | Wildcard) exclusions:[objectValue|LanguageStem +]? } |
| Wildcard | { | /* empty */ } |
| SemAct | { | name:IRI code:STRING? } |
| Annotation | { | predicate:IRI object:objectValue } |
| shapeExprLabel | = | IRI | BNODE ; |
| tripleExprLabel | = | IRI | BNODE ; |
| numericLiteral | = | INTEGER | DECIMAL | DOUBLE ; |
| ObjectLiteral | { | value:STRING language:STRING? type:STRING? } |
| Terminals | constrained by the terminal rules in the compact syntax | |
| PREFIX | : | PN_PREFIX |
| IRI | : | ( [^#0000- <>\"{}|^`\\] | UCHAR )* # (IRIREF without the enclosing "<>"s) |
| BNODE | : | BLANK_NODE_LABEL |
| BOOL | : | "true" | "false" # a JSON boolean value |
| INTEGER | : | INTEGER # a JSON string matching the lexical form of an integer |
| DECIMAL | : | DECIMAL # a JSON string matching the lexical form of an decimal |
| DOUBLE | : | DOUBLE # a JSON string matching the lexical form of an double |
| STRING | : | '"' .* '"' # a JSON string starting and ending with the U+0022 (") character |
| DATATYPE_STRING | : | '"' .* '"' ( [^#0000- <>\"{}|^`\\] | UCHAR )* # a JSON string starting with U+0022 ("), followed by the lexical form of the string, then U+0022 U+005E U+005E ("^^) and the IRI of the datatype |
| LANG_STRING | : | '"' .* '"@' LANGTAG # a JSON string starting with U+0022 ("), followed by the lexical form of the string, then U+0022 U+0040 ("@) and the LANGTAG |
The following schema describes the form of an RDF Graph conforming to a Shape Expression schema, consisten with the description of ShExJ.
This section has been submitted to the Internet Engineering Steering Group (IESG) for review, approval, and registration with IANA.
Fragment identifiers used with application/ld+json are treated as in RDF syntaxes, as per RDF 1.1 Concepts and Abstract Syntax [[RDF11-CONCEPTS]].
Consider requirements from Self-Review Questionnaire: Security and Privacy.
Since ShEx is intended to be a pure data exchange format for
validating RDF graphs, the ShExJ serialization SHOULD NOT be passed through a
code execution mechanism such as JavaScript's eval()
function to be parsed. An (invalid) document may contain code that,
when executed, could lead to unexpected side effects compromising
the security of a system.