Re: my proposed introduction to the SHACL document

This would replace the entirety of the abstract and Section 1.

peter


On 09/03/2015 06:38 PM, Holger Knublauch wrote:
> Could you clarify which section this is supposed to replace? It looks similar
> to 1.2 but covers much less material and fewer details.
> 
> Thanks
> Holger
> 
> 
> On 9/4/15 10:43 AM, Peter F. Patel-Schneider wrote:
>> I put together an introduction to the SHACL document that I think is much
>> better than the current one.  It presents a short description of the major
>> aspects of SHACL and then goes into a non-controversial example,.taken from
>> the SHACL primer and slightly modified.
>>
>> There are other parts of the SHACL document that also have bad introductory
>> material.  This new introduction does not, for example. alleviate the need for
>> some good introductory material about scopes and filters or about the
>> relationship between SHACL and SPARQL.
>>
>> peter
>>
>>
>>
>>
>>
>>
>> SHACL (Shapes Constraint Language) is a language for determining whether an
>> RDF graph (possibly in an RDF dataset) validates against certain shapes.
>> For example, SHACL can be used to check whether all the nodes in an RDF
>> graph that have a type link to foaf:Person have a single value for foaf:mbox
>> and that that value is an IRI.  SHACL can also be used to check whether a
>> particular node in an RDF graph, say the node ex:bug1, has at least one
>> value for ex:reportedBy and all such values have an rdf:type link to
>> foaf:Person.  In doing this checking, SHACL only looks at the triples that
>> are in the graph.
>>
>> The most general interface to SHACL has two arguments.  The first argument
>> is an RDF graph (in an RDF dataset) that contains the data that is to be
>> validated, which is called the data graph.  The second argument consists of
>> the shapes and other information that control what validation is to be done.
>> This control information can be itself encoded as an RDF graph, which is
>> called the control graph.
>>
>> So in SHACL one might want to determine whether RDF graphs contain
>> information about issues and users, such as each issue is in either an
>> unasssigned or an assigned state, and each issue has a reporter and each
>> such reporter has a precisely one string name and one or more IRI mailboxes.
>>
>> A control graph that does this validation has two shapes.  The first,
>> my:IssueShape contains the two constraints on issues.  The second,
>> my:UserShape, contains the two constraints on reporters.  The first shape
>> also contains scope information that here says that its constraints are to
>> be validated against all nodes that have an rdf:type link to ex:Issue.
>>
>> my:IssueShape a sh:Shape ;
>>      sh:classScope ex:Issue;
>>      sh:property [
>>          sh:predicate    ex:state ;
>>          sh:allowedValue (ex:unassigned ex:assigned) ;
>>          sh:minCount 1 ; sh:maxCount 1
>>      ] ;
>>      sh:property [
>>          sh:predicate    ex:reportedBy ;
>>          sh:valueShape   my:UserShape ;
>>          sh:minCount 1 ; sh:maxCount 1
>>      ] .
>>
>> my:UserShape a sh:Shape ;
>>      sh:property [
>>          sh:predicate    foaf:name ;
>>          sh:valueType    xsd:string ;
>>          sh:minCount 1 ; sh:maxCount 1
>>      ] ;
>>      sh:property [
>>          sh:predicate    foaf:mbox ;
>>          sh:nodeKind     sh:IRI ;
>>          sh:minCount 1
>>      ] .
>>
>> The following data graph might be validated against this control graph
>>
>> inst:Issue1 a ex:Issue ;
>>      ex:state        ex:unassigned ;
>>      ex:reportedBy   inst:User2 .
>>
>> inst:User2 a foaf:Person ;
>>      foaf:name       "Bob Smith" ;
>>      foaf:mbox       <mailto:bob@example.org> ;
>>      foaf:mbox       <mailto:rs@example.org> .
>>
>> inst:Issue3 a ex:Issue ;
>>      ex:state        ex:unsinged ;
>>      ex:reportedBy   inst:User4 .
>>
>> inst:User4 a foaf:Person ;
>>      foaf:name       "Bob Smith", "Robert Smith" ;
>>      foaf:mbox       <mailto:bob@example.org> ;
>>      foaf:mbox       <mailto:rs@example.org> .
>>
>> The SHACL validation would validate my:IssueShape against inst:Issue1 and
>> inst:Issue3.  Validating the first node would determine that inst:Issue1
>> satisfies the constraints in my:IssueShape, along the way determining that
>> inst:User2 satisfies the constraints in my:UserShape.  Validating the second
>> node would determine that inst:Issue3 violates the constraint on values for
>> ex:state, because ex:unsigned is not in the list of allowed values, and also
>> violates the constraint on values for ex:reportedBy, because inst:User4
>> violates the my:UserShape constraint on the maximum number of values for
>> foaf:name.
>>
> 
>

Received on Friday, 4 September 2015 01:40:41 UTC