This document summarizes an Apache Jena track presentation about SHACL (Shapes Constraint Language) in Apache Jena. The presentation introduces SHACL as a W3C standard for validating RDF graphs, provides examples of using SHACL shapes to validate FOAF profiles, and demonstrates the SHACL validation process. It also covers the SHACL compact syntax, SHACL-SPARQL constraints, SHACL operations, and Apache Jena's support for SHACL including command line tools and Fuseki validation services.

1. https://www.apachecon.com/acah2020/tracks/jena.html
Apache Jena track at ApacheCon@Home 2020
2020-09-28
SHACL in Apache Jena

2. Andy
Contributor to Apache Jena
Co-editor: SPARQL
Iotics : https://iotics.com/

3. Today
● About
● SHACL Core
○ Example walkthrough
● SHACL Compact syntax
● SHACL-SPARQL
● SHACL operations

4. SHACL
Describes what the data looks like
W3C standard: https://www.w3.org/TR/shacl/
Use for:
● Validation
● Schema
● HTML forms
● . . .

5. SHACL-AF
Also “SHACL Advanced features” : https://www.w3.org/TR/shacl-af/
● Custom Targets
● Rules
● Node expressions
● Functions
Active Community Group
https://www.w3.org/community/shacl/

6. Why validate?
● Unexpected data makes applications harder to write
● Unexpected data in a database is hard to clean up
● External data may be missing/incomplete/changed/. . .
● Unnoticed data changes
Unexpected or missing data is a signal
Доверяй, но проверяй
“Trust but verify”
-- Russian Proverb

7. SHACL
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .

8. SHACL
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
Example data
:AlbertEinstein
a foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.
Validation
● Good: foaf:givenName
● No foaf:AddressShape (not required)
● foaf:familyName -- not matched
● Bad: foaf:birthDate

9. Validation Report
[ a sh:ValidationReport ;
sh:conforms false ;
sh:result [
a sh:ValidationResult ;
sh:focusNode :AlbertEinstein ;
sh:resultMessage "..." ;
sh:resultPath foaf:birthDate ;
sh:resultSeverity sh:Violation ;
sh:sourceConstraintComponent sh:LessThanConstraintComponent ;
sh:sourceShape [] ;
sh:value "1979-03-14"^^xsd:date
]
] .

10. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
NodeShape URI: schema:PersonShape
… applies to resources of class foaf:Person
:AlbertEinstein rdf:type foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.

11. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
Property Shape
… property foaf:givenName
:AlbertEinstein rdf:type foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.

12. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
… property foaf:givenName
… … object must be an xsd:string
:AlbertEinstein rdf:type foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.

13. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:maxCount 1 ;
sh:lessThan foaf:deathDate ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
… property foaf:birthDate
… … there must be at most one
:AlbertEinstein rdf:type foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.

14. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:maxCount 1 ;
sh:lessThan foaf:deathDate ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
… property foaf:birthDate
… … value must be less than all values of foaf:deathDate
:AlbertEinstein rdf:type foaf:Person ;
foaf:givenName "Albert" ;
foaf:familyName "Einstein" ;
foaf:birthDate "1979-03-14"^^xsd:date ;
foaf:deathDate "1955-04-18"^^xsd:date ;
.

15. SHACL Walkthrough
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:maxCount 1 ;
sh:lessThan foaf:deathDate ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
… property schema:address
… … conforms to another node shape

16. SHACL Compact Syntax
schema:PersonShape
a sh:NodeShape ;
sh:targetClass foaf:Person ;
sh:property [
sh:path foaf:givenName ;
sh:datatype xsd:string ;
] ;
sh:property [
sh:path foaf:birthDate ;
sh:lessThan foaf:deathDate ;
sh:maxCount 1 ;
] ;
sh:property [
sh:path foaf:address ;
sh:node foaf:AddressShape ;
] .
shape schema:PersonShape -> foaf:Person {
foaf:givenName datatype=xsd:string .
foaf:birthDate [0..1] lessThan=foaf:deathDate .
foaf:address @foaf:AddressShape .
}

17. Targets
Classes
● sh:targetClass
● Implicit (with the class declaration)
sh:targetSubjectsOf property
● c.f. rdfs:domain
sh:targetObjectsOf property
● c.f. rdfs:range
sh:node
● Specific node
SPARQL targets (SHACL-af)

18. SHACL Core : Key concepts
Targets -- starting points
Node shapes
Property shapes and Paths
-- routes from starting points to nodes to validate
Constraints -- validations

19. Apache Jena
https://jena.apache.org/documentation/shacl/
● SHACL Core, SHACL SPARQL (the REC)
● SHACL Compact syntax - read and write
● Command line tools
○ Parse and print
○ Validate
● Fuseki service
○ Validate graph
○ Validate at node

20. SHACL SPARQL Constraints
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 ex: <http://example/>
## SHAPES
ex:prefixes
sh:declare [ sh:prefix "rdfs"; sh:namespace "http://www.w3.org/2000/01/rdf-schema#"^^xsd:anyURI; ] .
:sparqlShape
sh:targetClass :CLASS ;
sh:sparql [
# Test language tag is in capitals
sh:prefixes ex:prefixes ;
# Query to return violations.
sh:select """
SELECT $this ?value
WHERE {
$this rdfs:label ?value .
BIND(lang(?value) AS ?X)
FILTER (!isLiteral(?value) || lcase(?X) != ?X)
}
""" ;
] .
One violation for each result of the query.

21. SHACL Idiom
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 ex: <http://example/>
## Test whether the data graph is empty.
ex:global
a sh:NodeShape ;
sh:targetNode ex:anything ;
sh:sparql [
sh:select "SELECT * { ?s ?p ?o } LIMIT 1" ;
] .

22. Online
https://shacl.org/playground/

23. Online
users@jena.apache.org
Subscribe: users-subscribe@jena.apache.org
https://jena.apache.org/documentation/shacl/