Extending SHACL to RDF Datasets

Andy Seaborne

SHACL defines a set of validation conditions in a Shapes Graph. These are used to validate an RDF Graph to produce a validation report.

This note describes applying the SHACL Shapes Constraint Language to RDF Datasets.

Overview

Validation of a RDF Datasets is performed by associating a target graph with each shape in a “Shapes Dataset”. The target graph can be specified on each shape but can also be written to apply to groups of shapes.

Shapes graphs can be reused so that the same set of shapes is used to validate multiple graphs in the dataset. The shapes to used for a dataset are contained in a “Shapes Dataset”, a collection of shapes graphs and which defines the shapes to be applied to an RDF datasets with different sets of shapes for different graphs in the dataset and sharing of shapes between different target graphs.

The declaration prefix shx: <http://www.w3.org/ns/shacl-x#> is assumed in the definitions.

Target Graphs

shx:targetGraph defines graphs to apply a shape to. The property can be repeated.

Example: a shape that is scoped to data graph data:namedGraph1:

:nodeShape0
    shx:targetGraph data:namedGraph1 ;
    sh:targetObjectsOf ns:q ;
    sh:datatype xsd:integer ;
    .

Certain URIs define a collection of graphs in the target dataset. The shape applies to each of the graphs as the data graph.

URI Graphs
shx:all All the graphs (named and default) of the data dataset.
shx:named All the named graphs of the data dataset.
shx:default The default graph of the data dataset.
shx:union The union graph formed from all named graphs of the data dataset.

The subject of the shx:targetGraph triple defines the scope - it can be a specific shape, a named graph of the shapes dataset or the whole shapes dataset (when the subject is the URI of the shapes dataset).

# Shapes Named graph
<#gn1> shx:targetGraph data:namedGraph1 .
GRAPH <#gn1> {
    :nodeShape0
        sh:targetObjectsOf ns:q ;
        sh:datatype xsd:integer ;
}

# Shapes Dataset
# All shapes in the shape dataset apply to all graphs in the data dataset.
<> shx:targetGraph shx:all .

:nodeShape0
    sh:targetObjectsOf ns:q ;
    sh:datatype xsd:integer ;
}

Validating with a target of shx:union is performed on the union of the named graph so the triples used to fulfil a shape may be in different graph. For example, if a shape defines a number of required properties ("sh:minCount 1"), these may be in different named graphs, but if present in the union graph, validating suceeds.

shx:targetGraphExclude defines graphs to be excluded from the target graphs. This target condition is applied after calculating the included target graphs for a shape.

URI Definition
shx:targetGraph Property identifying a data graph to target
shx:targetGraphExclude Property identifying a data graph to exclude as a target

Validation Reports

Each validation result in a validation report should have a shx:resultGraph triple whose object is the graph in which the validation report occurs. It is the shape’s shx:targetGraph if that is given, the graph name matching shx:targetGraphPattern or the specific named graph of the data dataset in the case of shx:named or shx:all.

URI Definition
shx:resultGraph Data graph that caused the validation result

Grouping Shapes

The graphs of the shapes dataset can be used to group shapes. If a shx:targetGraph triple has a graph name as subject, then the target rule is applied as the default rule for all shapes in that shapes graph. The shape graph graph name does not need to correspond to any graph in the data to be validated.

The shx:targetGraph can be in the default graph of the shapes datset or in a named graph. These two examples achive the same effect.

<#g> shx:targetGraph data:graphName .
GRAPH <#g> {
   ... any shapes in graph <#g> will have the targetGraph scope above ...
}

GRAPH <#g> {
   <#g> shx:targetGraph data:graphName .
   ... any shapes in graph <#g> will have the targetGraph scope above ...
}

The grouping rules applies to shx:targetGraphExclude as well.

Sharing Common Shapes Patterns

The property shx:include can be used to include triples from another named graph of the shapes dataset. A typical use is to include shapes from another graph which does not have a shx:targetGraph, using it like a includes library.

If the subject is the URI of the shapes dataset, the inclusion is into declaration applies to the whole dataet (all shapes graphs), otherwise it is to the named graph of the subject of the triple.

It is similar to owl:imports except the inclusion is named by the subject and only applies to including graphs within the shapes dataset.

shx:include is applied transitively.

Examples

Examples are written in TriG.

Assumed prefixes:

PREFIX rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
PREFIX rdfs:    <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd:     <http://www.w3.org/2001/XMLSchema#>

PREFIX sh:      <http://www.w3.org/ns/shacl#>
PREFIX shx:     <http://www.w3.org/ns/shacl-x#>

PREFIX data:    <http:/example/data/>
PREFIX s:       <http:/example/shapes/>
PREFIX ns       <http:/example/ns#>

Examples

Apply all shapes to all graphs in the data.

<> shx:targetGraph shx:all .

:nodeShape0
    shx:targetGraph data:namedGraph1 ;
    sh:targetObjectsOf ns:q ;
    sh:datatype xsd:integer ;
    .

Example

All shapes applied to a specific named graph.

<> shx:targetGraph data:namedGraph1 .

:nodeShape0
    sh:targetObjectsOf ns:q ;
    sh:datatype xsd:integer ;
    .

:nodeShape1
    sh:targetObjectsOf ns:p ;
    sh:datatype xsd:subject ;
    .

Example

A collection of shapes for one graph.

GRAPH <#g1> {
     <#g1> shx:targetGraph data:namedGraph1 .

    :nodeShape0
        sh:targetObjectsOf ns:q ;
        sh:datatype xsd:integer .

    :nodeShape1
        sh:targetObjectsOf ns:q ;
        sh:class ns:class .
}

Example

Apply to all graphs except data:namedGraph1.

<> shx:targetGraph data:all ;
   shx:targetGraphExclude data:namedGraph1 .

Possible additions

Graph name patterns

For targets, a regular expression to filter the data dataset graph names based on URIs:

[] shx:targetGraphPattern "http://example/.*/shapes" .

[] shx:targetGraphPattern ("http://example/shapes/set-\\d{1,4}" . "i") .

Similarly shx:targetGraphExcludePattern.

Dataset-level constraints

Constraints on graphs and graph names (e.g. URI pattern of gah names).

These can be done by escaping to SPARQL and a global constraint but if there are some common constraints, then including a direct form would be useful.