Short introduction to SHACL language for validation of RDF data

1. Validation of RDF Data
Jean-Paul Calbimonte
University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis)
Zurich, December 2017
@jpcik

2. 2
HES-SO:
University of Applied Sciences and Arts Western Switzerland
We are here,
In the heart of the Valais!

3. 3
Thanks to José Emilio Labra et al.
RDF and Linked Data Validation (ESWC 2016)
materials adapted from:
http://weso.github.io/RDFValidation_ESWC16/

4. 4
Validation of RDF Data
a reminder …

5. 5
RDF
University of Zurich City of Zurich
is located in
The University of Zurich
is located in the city of
Zurich
A triple:
http://dbpedia.org/resource/University_of_Zurich http://dbpedia.org/resource/Zürich
http://dbpedia.org/ontology/cityAn RDF triple:
<http://dbpedia.org/resource/University_of_Zurich> <http://dbpedia.org/ontology/city> <http://dbpedia.org/resource/Zürich>.
An RDF triple in N-Triples format:

6. 6
RDF graphs
http://dbpedia.org/resource
/University_of_Zurich
http://dbpedia.org
/resource/Zürichhttp://dbpedia.org/ontology/city
1833 http://dbpedia.org/property/established
xsd:integer
3702
xsd:integer http://dbpedia.org/ontology/facultySize
http://dbpedia.org/
ontology/University
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/resource
/Doris_Leuthard
http://dbpedia.org/ontology/almaMater
http://dbpedia.org/resource/President
_of_the_Swiss_Confederation
http://dbpedia.org/resource
/Merenschwand
1963-04-10
LeuthardDoris
http://dbpedia.org/resource
/ETH_Zurich
http://dbpedia.org/
ontology/city
http://xmlns.com/foaf/0.1
/givenName
http://xmlns.com/foaf/0.1
/surname
http://dbpedia.org/ontology
/birthDate
http://dbpedia.org/
ontology/birthPlace
http://dbpedia.org/
property/title
xsd:date
xsd:string xsd:string

7. 7
RDF Turtle Format
prefix db: <http://dbpedia.org/resource/>
prefix dbo: <http://dbpedia.org/ontology/>
prefix dbp: <http://dbpedia.org/property/>
prefix foaf:<http://xmlns.com/foaf/0.1/>
db:University_of_Zurich dbo:city db:Zürich ;
dbp:established 1833 ;
dbo:facultySize 3702^^xsd:integer ;
dbp:almaMater db:Doris_Leuthard .
db:Doris_Leuthard dbp:birthDate "1963-04-10"^^xsd:date;
foaf:givenName "Doris";
foaf:surname "Leuthard";
dbo:birthPlace db:Merenschwand;
dbp:title db:President_of_the_Swiss_Confederation .
URIs
Literals
Predicate URIs

8. 8
Validation of RDF Data
and now validation …

9. 9
Why RDF Validation?
• Understand data contents
• Expected structure
• Describe data requirements
• Data guarantees
• Verifiable structure/contents
• Query processing
• Optimizations
In other technologies:
RDB: DDL
XML: DTD/XML Schema
JSON: JSON Schema

10. 10
Use OWL?
ex:almaMater
a owl:ObjectProperty ;
rdfs:domain ex:Person ;
rdfs:range ex:University ;
Different purpose
Different level of abstraction
OWL -> ontology modeling

11. 11
Validation Alternatives
• SPARQL queries
• SPIN
• Stardog ICV (based on OWL)
• OSLC Resource shapes
• RDFUnit
• RDF data descriptors
• ShEx expressions
what we will see today:
SHACL: W3C Recommendation (July 2017)

12. 12
Shapes Constraint Language SHACL
https://www.w3.org/TR/shacl/
• Language for validating RDF graphs
• Conditions represented as shapes
• Shapes expressed in RDF
• SPARQL-based extensions
• W3C Recommendation

13. 13
SHACL Basics
Shape
Node Shape Property Shape
shapes about
the focus node
shapes about the values
of a property/path
how to validate a focus node based on:
- values of properties
- other characteristics
Focus Node
An RDF term that is validated
against a shape
Constraint
componentsTarget
Target declarations can be
used to produce focus nodes
for a shape
Determine how to
validate a node

14. 14
SHACL: an example
ex:CityShape
a sh:NodeShape ;
sh:targetClass ex:City ;
sh:property [
sh:path ex:population ;
sh:maxCount 1 ;
sh:datatype xsd:integer ;
] .
it is a node shape
applies to all cities
constraint the values
of ex:population
max 1 population
of type integer
e.g. "all cities have at
most one population
property of type
integer"
ex:London a ex:City ;
ex:population "two million" .
ex:Paris a ex:City ;
ex:population 2304 ;
ex:population 5342 ;

15. 15
Targets
Declare the focus nodes for a shape
Node target: ex:CityShape
a sh:NodeShape ;
sh:targetNode ex:Zurich .
ex:London a ex:City ;
ex:Zurich a ex:City ;
directly declare nodes
Class target:
nodes with a given type
ex:CityShape
a sh:NodeShape ;
sh:targetClass ex:City .
Implicit class target:
same, but implicit
ex:City
a rdfs:Class, sh:NodeShape .
ex:Luzern a ex:City .
ex:Olten a ex:City .
ex:Valais a ex:Canton .
ex:SwissCity
rdfs:subClassOf ex:City .
ex:Basel a ex:SwissCity .
ex:Munich a ex:GermanCity .
ex:Lausanne a ex:City .
ex:Limmat a ex:River .
target subject of, target object of: see docs.

16. 16
Node Shapes
:University
a sh:NodeShape ;
sh:nodeKind sh:IRI .
:epfl a :University.
<http://example.ch/unifr> a :University .
_:1 a :University .
Constraints about a focus node
sh:BlankNode
sh:IRI
sh:Literal
sh:BlankNodeOrIRI
sh:BlankNodeOrLiteral
sh:IRIOrLiteral
Possible values:

17. 17
Property Shapes
Constraints about a given property and its values for the focus node
- sh:property associates a shape with a property constraint
- sh:path identifies the path
:Student a sh:NodeShape ;
sh:property [
sh:path ex:email;
sh:nodeKind sh:IRI
] .
:anna a :Student ;
ex:email <mailto:anna@uzh.ch> .
:max a :Student ;
ex:email <mailto:max@uzh.ch> .
:greta a :Student ;
ex:email "greta@uzh.ch" .

18. 18
Disclaimer:
target declarations sometimes
omitted in the following examples

19. 19
Core constraint components
Value Type: class, datatype, nodeKind
Cardinality: minCount, maxCount
Value Range: minInclusive, maxInclusive, minExclusive, maxExclusive
String-based: minLength, maxLength, pattern, languageIn, uniqueLang
Property Pair: equals, disjoint, lessThan, lessThanOrEquals
Logical: not, and, or, xone
Shape-based: node, property, qualifiedValueShape, qualifiedMinCount,
qualifiedMaxCount
On values: in, hasValue
Closed shapes: closed, ignoredProperties
Non-validating: name, description, order, group, defaultValue
SPARQL: sparql

20. 20
Value Type Constraints: Datatype
sh:datatype: condition to be satisfied for the datatype of each value node.
:University a sh:NodeShape ;
sh:property [
sh:path ex:established;
sh:datatype xsd:date ;
] .
:hes-so ex:established "1997-01-20"^^xsd:date .
:eth ex:established "Unknown"^^xsd:date .
:uzh ex:established 1990 .

21. 21
Value Type Constraints: Class
sh:class condition: each value node is a SHACL instance of a given type.
:Person
a sh:NodeShape, rdfs:Class ;
sh:property [
sh:path ex:almaMater ;
sh:class :University
] .
:unifr a :University .
:eth a :FederalSchool .
:unibe a :CantonalUniversity
:FederalSchool rdfs:subClassOf :University .
:anna a :Person;
ex:almaMater :unifr .
:max a :Person ;
ex:almaMater :eth .
:greta a :Person;
ex:almaMater :unibe .

22. 22
Value Type Constraints: Kind
sh:nodeKind: condition to be satisfied by the RDF node kind
:Student
a sh:NodeShape, rdfs:Class ;
sh:property [
sh:path ex:name ;
sh:nodeKind sh:Literal ;
];
sh:property [
sh:path ex:friendOf ;
sh:nodeKind sh:BlankNodeOrIRI
];
sh:nodeKind sh:IRI .
:anna a :Student;
ex:name _:1 ;
ex:friendOf :max .
:max a :Student;
ex:name "Max";
ex:friendOf [ex:name "Lucas"] .
:greta a :Student;
ex:name "Greta" ;
ex:friendOf "Lucas" .
_:1 a :Student.
BlankNode, IRI, Literal,
BlankNodeOrIRI, IRIOrLiteral
BlankNodeOrLiteral,
possible
kinds

23. 23
Cardinality constraints
sh:minCount: minimum number of value nodes that satisfy the condition
sh:maxCount: maximum number of value nodes that satisfy the condition.
:Student a sh:NodeShape ;
sh:property [
sh:path ex:hasCourse ;
sh:minCount 2 ;
sh:maxCount 3 ;
] .
:anna ex:hasCourse
:math, :physics .
:max ex:hasCourse
:chemistry .
:greta ex:hasCourse
:math, :physics,
:chemistry, :history .

24. 24
Value Range Constraints
Value range conditions for value nodes that are comparable via operators
such as <, <=, > and >=. sh:minInclusive, sh:maxInclusive,
sh:minExclusive, sh:maxExclusive
:Grade a sh:NodeShape ;
sh:property [
sh:path ex:gradeValue ;
sh:minInclusive 1 ;
sh:maxInclusive 5 ;
sh:datatype xsd:integer
] .
:failure ex:gradeValue 1 .
:sufficient ex:gradeValue 3 .
:excelent ex:gradeValue 5 .
:toobad ex:gradeValue 0 .

25. 25
String-based Constraints
Specify conditions on the string representation of value nodes.
sh:minLength: minimum string length of each value node.
sh:maxLength: maximum string length of each value node.
sh:pattern: regular expression that each value node matches.
sh:languageIn: allowed language tags for each value node.
sh:uniqueLang: no pair of value nodes may use the same language tag.

26. 26
minLength/maxLength
:Student a sh:NodeShape ;
sh:property [
sh:path ex:name ;
sh:minLength 4 ;
sh:maxLength 10 ;
] .
:anna ex:name "Anna" .
:max ex:name "Max" .
:greta ex:name :Greta .
:strange ex:name _:strange .
sh:minLength: minimum string length of each value node.
sh:maxLength: maximum string length of each value node.

27. 27
pattern
:Student a sh:NodeShape ;
sh:property [
sh:path ex:studentID ;
sh:pattern "^Pd{3,4}" ;
sh:flags "i" ;
] .
:anna ex:studentID "P2345" .
:max ex:studentID "p567" .
:greta ex:studentID "P12" .
:lara ex:studentID "B123" .
sh:pattern: regular expression that each value node matches.

28. 28
languageIn
ex:SwissLangShape a sh:NodeShape ;
sh:targetNode ex:Mountain, ex:Berg ;
sh:property [
sh:path ex:prefLabel ;
sh:languageIn ( "en" "fr" ) ;
] .
ex:Mountain
ex:prefLabel "Mountain"@en ;
ex:prefLabel "Hill"@en-UK ;
ex:prefLabel "Montagne"@fr .
ex:Berg
ex:prefLabel "Berg" ;
ex:prefLabel "Berg"@de ;
ex:prefLabel ex:BergLabel .
sh:languageIn: allowed language tags for each value node.

29. 29
uniqueLang
:Canton a sh:NodeShape ;
sh:property [
sh:path ex:name ;
sh:uniqueLang true
] .
:valais ex:name
"Valais"@fr, "Wallis"@de .
:fribourg ex:name
"Fribourg"@fr,
"Freiburg"@de,
"Friburgo"@es .
:zurich ex:name
"Zurich"@de, "Zuerich"@de.
sh:uniqueLang: no pair of value nodes may use the same language tag.

30. 30
Property Pair Constraints
Specify conditions on the sets of value nodes in relation to other properties.
sh:equals: all value nodes equal to the objects of the focus node
sh:disjoint: value nodes is disjoint with the objects of the focus node
sh:lessThan: each value node is smaller than all the objects of focus node
sh:lessThanOrEquals: same, but smaller than or equal

31. 31
equals
:Student a sh:NodeShape ;
sh:property [
sh:path ex:givenName ;
sh:equals ex:firstName
];
:anna ex:givenName "Anna";
ex:lastName "Parker";
ex:firstName "Anna" .
:max ex:givenName "Max";
ex:lastName "Sutter" ;
ex:firstName "Maximilian" .
:greta ex:givenName "Greta";
ex:lastName "Greta" ;
ex:firstName "Greta" .
sh:equals: all value nodes equal to the objects of the focus node

32. 32
disjoint
:Student a sh:NodeShape ;
sh:property [
sh:path ex:givenName ;
sh:disjoint ex:lastName
] .
:anna ex:givenName "Anna";
ex:lastName "Parker";
ex:firstName "Anna" .
:max ex:givenName "Max";
ex:lastName "Sutter" ;
ex:firstName "Maximilian" .
:greta ex:givenName "Greta";
ex:lastName "Greta" ;
ex:firstName "Greta" .
sh:disjoint: value nodes is disjoint with the objects of the focus node

33. 33
lessThan/lessThanOrEquals
ex:LessThanShape a sh:NodeShape ;
sh:property [
sh:path ex:startDate ;
sh:lessThan ex:endDate ;
] .
:project
ex:startDate "2017-01-02"^^xsd:date ;
ex:endDate "2015-01-02"^^xsd:date .

34. 34
Logical Constraints
Implement the common logical operators and, or, not, xone (kind of xor)
sh:and: Conjunction of a list of shapes
sh:or: Disjunction of a list of shapes
sh:not: Negation of a shape
sh:xone: Exactly one (similar XOR for 2 arguments)

35. 35
not
ex:NotShape a sh:NodeShape ;
sh:targetNode :anna ;
sh:not [
a sh:PropertyShape ;
sh:path ex:established ;
sh:minCount 1 ;
] .
:anna ex:established "Some value" .
sh:not: Negation of a shape

36. 36
and
ex:Shape1 a sh:NodeShape ;
sh:property [
sh:path ex:courses ;
sh:minCount 1 ;
] .
ex:Shape2 a sh:NodeShape ;
sh:targetNode :anna, :max ;
sh:and (
ex:Shape1
[ sh:path ex:courses ;
sh:maxCount 1 ; ]
) .
:anna ex:courses "Math" .
:max ex:courses "Math" ;
ex:courses "Chemistry" .
sh:and: Conjunction of a list of shapes

37. 37
or
ex:OrShape a sh:NodeShape ;
sh:targetNode :anna, :max ;
sh:or (
[ sh:path ex:firstName ;
sh:minCount 1 ; ]
[ sh:path ex:givenName ;
sh:minCount 1 ; ]
) .
:anna ex:firstName "Anna" .
:max ex:givenName "Max" .
sh:or: Disjunction of a list of shapes

38. 38
or
ex:AddressShape a sh:NodeShape ;
sh:targetClass ex:Student ;
sh:property [
sh:path ex:address ;
sh:or (
[ sh:datatype xsd:string ; ]
[ sh:class ex:Address ; ]
)
] .
:anna
ex:address "12 Petit Rue, 1220,
Geneva" .
:max ex:address :maxAddress .
:maxAddress a ex:Address ;
ex:street "Grand Rue" ;
ex:zip 3960 ;
ex:locality ex:Sierre .
sh:or: Disjunction of a list of shapes

39. 39
xone
ex:XoneShape a sh:NodeShape ;
sh:targetClass ex:Person ;
sh:xone (
[ sh:property
[ sh:path ex:fullName ;
sh:minCount 1 ; ]
]
[ sh:property
[ sh:path ex:firstName ;
sh:minCount 1 ; ] ;
sh:property
[ sh:path ex:lastName ;
sh:minCount 1 ; ]
]
) .
ex:Bob a ex:Person ;
ex:firstName "Robert" ;
ex:lastName "Coin" .
ex:Carla a ex:Person ;
ex:fullName "Carla Miller" .
ex:Dory a ex:Person ;
ex:firstName "Dory" ;
ex:lastName "Dunce" ;
ex:fullName "Dory Dunce" .
sh:xone: conforms to exactly one of the provided shapes.

40. 40
Shape-based Constraints
Specify complex conditions by validating the value nodes against certain shapes.
sh:node: each value node conforms to the given node shape.
sh:property: specify that each value node has a given property shape.
sh:qualifiedValueShape: a number of value nodes conforms to a given shape.
- one value for sh:qualifiedMinCount
- one value for sh:qualifiedMaxCount
- one value for each

41. 41
node
ex:AddressShape a sh:NodeShape ;
sh:property [
sh:path ex:postalCode ;
sh:datatype xsd:string ;
sh:maxCount 1 ;
] .
ex:PersonShape a sh:NodeShape ;
sh:targetClass ex:Person ;
sh:property [
sh:path ex:address ;
sh:minCount 1 ;
sh:node ex:AddressShape ;
] .
ex:Bob a ex:Person ;
ex:address ex:BobsAddress .
ex:BobsAddress ex:postalCode "1234" .
ex:Reto a ex:Person ;
ex:address ex:RetosAddress .
ex:RetosAddress ex:postalCode 5678 .
sh:node: each value node conforms to the given node shape.

42. 42
property, qualifiedValueShape
ex:QualifiedShape a sh:NodeShape ;
sh:targetNode ex:anna, ex:max ;
sh:property [
sh:path ex:parent ;
sh:minCount 2 ;
sh:maxCount 2 ;
sh:qualifiedValueShape [
sh:path ex:gender ;
sh:hasValue ex:female ; ] ;
sh:qualifiedMinCount 1 ;
] .
ex:John ex:gender ex:male .
ex:Jane ex:gender ex:female .
ex:Tim ex:gender ex:male .
ex:anna
ex:parent ex:John ;
ex:parent ex:Jane .
ex:max
ex:parent ex:John ;
ex:parent ex:Tim .
sh:property: specify that each value node has a given property shape.

43. 43
Constraints on values: hasValue
sh:hasValue: at least one value node is equal to the given RDF term.
ex:ETHGraduate a sh:NodeShape ;
sh:targetNode :anna ;
sh:property [
sh:path ex:alumniOf ;
sh:hasValue ex:ETH ;
] .
:anna ex:alumniOf ex:EPFL ;
ex:alumniOf ex:ETH .

44. 44
Constraints on values: in
sh:in: each value node is a member of a provided SHACL list.
ex:InShape a sh:NodeShape ;
sh:targetClass ex:SkiSlope ;
sh:property [
sh:path ex:difficulty ;
sh:in ( ex:Black ex:Blue ex:Red ) ;
] .
ex:slope1 a ex:SkiSlope;
ex:difficulty ex:Pink .
ex:slope2 a ex:SkiSlope;
ex:difficulty ex:Red .

45. 45
Closed shapes
sh:closed Set to true to close the shape.
sh:ignoredProperties
Optional properties that are also permitted in addition to those
explicitly enumerated via sh:property.
ex:ClosedShape a sh:NodeShape ;
sh:targetNode ex:Alice, ex:Bob ;
sh:closed true ;
sh:ignoredProperties (rdf:type) ;
sh:property [ sh:path ex:firstName ; ] ;
sh:property [ sh:path ex:lastName ; ] .
ex:Alice ex:firstName "Alice" .
ex:Bob ex:firstName "Bob" ;
ex:middleInitial "J" .

46. 46
Non-validating constraints
sh:name: provide human-readable labels for the property.
sh:description: provide descriptions of the property in the given context.
sh:order: indicate the relative order of the property shape for purposes
such as form building.
sh:group: indicate that the shape belongs to a group of related property
shapes.
Property shapes may have a single sh:defaultValue. The default value
does not have fixed semantics

47. 47
Non validating constraints
ex:PersonFormShape a sh:NodeShape ;
sh:property [
sh:path ex:firstName ;
sh:name "first name" ;
sh:description "The given name(s)" ;
sh:order 0 ;
sh:group ex:NameGroup ; ] ;
sh:property [
sh:path ex:lastName ;
sh:name "last name" ;
sh:description "The last name" ;
sh:order 1 ;
sh:group ex:NameGroup ; ] ;
Name
Address
sh:property [
sh:path ex:streetAddress ;
sh:name "street address" ;
sh:description "The street address" ;
sh:order 11 ;
sh:group ex:AddressGroup ; ] ;
sh:property [
sh:path ex:locality ;
sh:name "locality" ;
sh:description "The town or city " ;
sh:order 12 ;
sh:group ex:AddressGroup ; ] ;
sh:property [
sh:path ex:postalCode ;
sh:name "postal code" ;
sh:name "zip code"@en-US ;
sh:description "The postal code" ;
sh:order 13 ;
sh:group ex:AddressGroup ; ] .
ex:NameGroup a sh:PropertyGroup ;
sh:order 0 ;
rdfs:label "Name" .
ex:AddressGroup a sh:PropertyGroup ;
sh:order 1 ;
rdfs:label "Address" .

48. 48
SPARQL
PREFIX ex: <http://example.com#>
SELECT ?name ?university
WHERE {
?student ex:lastName ?name ;
ex:attends ?university .
?university ex:name ?uniname .
FILTER (langMatches(lang(?uniname), "fr"))
}

49. 49
SPARQL-based constraints
ex:LanguageShape a sh:NodeShape ;
sh:targetClass ex:Country ;
sh:sparql [
a sh:SPARQLConstraint ;
sh:message "Values are literals with German language tag." ;
sh:prefixes ex: ;
sh:select """ SELECT $this (ex:germanLabel AS ?path) ?value
WHERE {
$this ex:germanLabel ?value .
FILTER (!isLiteral(?value) ||
!langMatches(lang(?value), "de"))
} """ ;
] .
ex:country1 a ex:Country ;
ex:germanLabel "Spanien"@de .
ex:country2 a ex:Country ;
ex:germanLabel "Spain"@en .

50. 50
Shape Messages
ex:MyShape a sh:NodeShape ;
sh:targetNode ex:MyInstance ;
sh:property [
sh:path ex:myProperty ;
sh:minCount 1 ;
sh:datatype xsd:string ;
sh:severity sh:Warning ; ] ;
sh:property [
sh:path ex:myProperty ;
sh:maxLength 10 ;
sh:message "Too many characters"@en ;
sh:message "Zu viele Zeichen"@de ; ] ;
sh:deactivated true .

51. 51
ShEx
:User IRI {
schema:name xsd:string
}
:User a sh:NodeShape, rdfs:Class ;
sh:targetClass :Person ;
sh:nodeKind sh:IRI ;
sh:property [
sh:path schema:name ;
sh:datatype xsd:string
] .
Shape expressions: http://shex.io/
SHACL ShEx

52. 52
ShEx
:User {
schema:givenName xsd:string
schema:lastName xsd:string
}
:User a sh:NodeShape ;
sh:property [
sh:path schema:givenName ;
sh:datatype xsd:string ;
];
sh:property [
sh:path schema:lastName ;
sh:datatype xsd:string ;
] .
:alice schema:givenName "Alice" ;
schema:lastName "Cooper" .
:bob schema:givenName "Bob", "Robert" ;
schema:lastName "Smith", "Dylan" .
:carol schema:lastName "King" .
:dave schema:givenName 23;
schema:lastName :Unknown .

53. 53
Validation of RDF Data
a lot more info on the docs of SHACL and ShEx

54. ¡gracias! ¿tienes preguntas?
Jean-Paul Calbimonte
University of Applied Sciences and Arts Western Switzerland
HES-SO Valais-Wallis
@jpcik