Shape Constraints & Expressions — Interactive Learning Companion

🔍 Chapter 7 Topic Explorer

Explore each core topic from Chapter 7. Select a category to see syntax, semantics, and annotated examples.

// Select a topic above to explore Chapter 7 features

📚 Chapter 7 in context: SPARQL (Ch. 6) lets you query RDF graphs. SHACL and ShEx (Ch. 7) let you validate them — enforcing structural constraints that the open-world assumption of OWL/RDFS cannot provide.

🧪 Shape Authoring Sandbox

Explore how SHACL shapes are written. Load an example, edit it, and see a live parse of the shape graph structure.

⚠️ Key Rule: A SHACL shape graph is itself valid RDF. Shapes can be stored in a named graph, queried with SPARQL, and versioned alongside your ontology. Validation is always graph vs shapes graph.

✅ Validation Simulator

Step through how a SHACL processor evaluates a data graph against a shapes graph. See which nodes conform and which violate.

Select a scenario above to begin the validation walkthrough

💡 Key Insight: Validation is closed-world — if an expected property is absent, it is a violation. This is the opposite of OWL's open-world assumption. A node conforms only when ALL constraints in all applicable shapes evaluate to TRUE.

🧱 Constraint Component Lab

Explore the full set of SHACL constraint components and the SHACL vs ShEx comparison. Click a tip to expand it.

Core SHACL Constraint Components

Constraint	Category	What it checks	Example
sh:minCount / sh:maxCount	Cardinality	Min/max number of values for the path	sh:minCount 1
sh:datatype	Value Type	All values must be a given XSD datatype	sh:datatype xsd:string
sh:class	Value Type	All values must be instances of a given class	sh:class ex:Person
sh:nodeKind	Value Type	IRI, BlankNode, or Literal	sh:nodeKind sh:IRI
sh:minExclusive / sh:maxInclusive	Range	Numeric value range bounds	sh:minInclusive 0
sh:minLength / sh:maxLength	String	Literal string length bounds	sh:minLength 1
sh:pattern	String	Value must match a regular expression	sh:pattern "^\\d{4}-"
sh:in	Enumeration	Value must be in a given list	sh:in (ex:A ex:B)
sh:hasValue	Enumeration	At least one value must equal a given node	sh:hasValue ex:X
sh:node	Shape	All values must conform to another shape	sh:node ex:PersonShape
sh:and / sh:or / sh:not	Logical	Boolean combinations of shapes	sh:or ( [...] [...] )
sh:sparql	SPARQL	SPARQL SELECT — any row = violation	sh:sparql [ sh:select ... ]

⚖️ SHACL vs ShEx — Click to expand

📐 Syntax: SHACL uses Turtle/RDF; ShEx has its own compact syntax

🎯 Targets: sh:targetClass vs Shape Map

🔄 Recursion: ShEx supports it natively; SHACL Core does not

⚡ Extensibility: SHACL-SPARQL vs Semantic Actions

🏥 Real-world adoption: enterprise vs biomedical

🏆 W3C Status: SHACL is a full Recommendation; ShEx is a Submission

🔗 Property Path Types in SHACL

SHACL sh:path supports rich SPARQL-style property paths:

Predicate Path

sh:path ex:name — validates values of a single predicate at the focus node.

Inverse Path

sh:path [ sh:inversePath ex:knows ] — validates nodes that point TO the focus node.

Sequence Path

sh:path ( ex:worksFor ex:name ) — chain two predicates; validates the employer's name.

Alternative / OneOrMore

sh:alternativePath, sh:oneOrMorePath, sh:zeroOrMorePath — mirrors SPARQL property paths.

🎮 SHACL Challenge

Test your knowledge of SHACL, ShEx, and shape-based validation. 10 points per correct answer!

Score: 0 / 100 Question - of 10

Press "Start" to begin the SHACL Challenge!

📝 Chapter 7 Quiz

12 questions covering SHACL, Shape Graphs, Validation, and ShEx. You can review answers before finishing.

1. Which W3C document defines SHACL?

SPARQL 1.1 Overview

Shapes Constraint Language (SHACL) — W3C Recommendation 2017

OWL 2 Web Ontology Language — W3C Recommendation

RDF Schema — W3C Recommendation

1 / 12

📄 Chapter 7 Cheat Sheet

Key syntax, rules, and patterns for SHACL and ShEx. Keep this open during revision.

🛡️ SHACL Shape Declaration

Node shape targeting a class:

ex:MyShape a sh:NodeShape ;
  sh:targetClass ex:Person ;
  sh:property [ sh:path ex:name ;
    sh:minCount 1 ;
    sh:datatype xsd:string ] .

Other target types:

sh:targetNode ex:alice       # specific node
sh:targetSubjectsOf ex:p    # all subjects of p
sh:targetObjectsOf  ex:p    # all objects of p

📊 Cardinality & Value Type

Cardinality constraints:

sh:minCount 1        # at least 1 value
sh:maxCount 1        # at most 1 value
sh:minCount 1 ; sh:maxCount 1  # exactly 1

Value type constraints:

sh:datatype xsd:string
sh:datatype xsd:integer
sh:class    ex:Person
sh:nodeKind sh:IRI
sh:nodeKind sh:Literal
sh:nodeKind sh:BlankNode

🔀 Logical Constraints

Boolean combinations:

sh:and ( ex:ShapeA ex:ShapeB )
sh:or  ( ex:ShapeA ex:ShapeB )
sh:not ex:ForbiddenShape
sh:xone ( ex:A ex:B )  # exactly one

Closed shape (no extra properties):

sh:closed true ;
sh:ignoredProperties ( rdf:type ) ;

✅ Validation Report Structure

sh:ValidationReport:

[ a sh:ValidationReport ;
  sh:conforms false ;
  sh:result [
    sh:focusNode ex:bob ;
    sh:resultPath ex:name ;
    sh:sourceConstraintComponent
      sh:MinCountConstraintComponent ;
    sh:resultMessage "Missing name"
  ]
]

Severity levels (set on any shape):

sh:severity sh:Violation  # default
sh:severity sh:Warning
sh:severity sh:Info

📐 ShEx Compact Syntax (ShExC)

Basic shape:

<PersonShape> {
  ex:name  xsd:string  MinLength 1 ;
  ex:email IRI         +           ;
  ex:age   xsd:integer MinInclusive 0 ?
}
# ? = optional  + = 1+  * = 0+

Recursive shape & shape map:

<OrgShape> {
  ex:name   xsd:string ;
  ex:subOrg @<OrgShape> *  # recursive!
}
# Shape map (node → shape binding):
<http://ex.org/alice> @ <PersonShape>

⚖️ SHACL vs ShEx Quick Reference

Key differences at a glance:

Feature        SHACL          ShEx
────────────────────────────────────
Syntax         Turtle/RDF     ShExC / ShExJ
Targets        sh:target*     Shape Map
Recursion      ✗ Core         ✓ Native
W3C Status     Rec (2017)     Sub (2019)
Extensible     SHACL-SPARQL   Semantic Actions
Tooling        Jena, RDF4J    shex.js, PyShEx
Best for       Enterprise KG  Biomedical/Wiki

⚡ SHACL-SPARQL Constraint

Embed a SPARQL SELECT — any row = violation:

ex:AgeShape a sh:NodeShape ;
  sh:targetClass ex:Person ;
  sh:sparql [
    sh:message "Age inconsistent" ;
    sh:prefixes ex: ;
    sh:select """
      SELECT $this WHERE {
        $this ex:birthYear ?by ;
               ex:age ?age .
        FILTER(?age != (2024 - ?by))
      }"""
  ] .

🏆 Best Practices

Author & validate effectively:

✓ Give shapes URIs (not blank nodes)
✓ Add sh:message to every constraint
✓ Use sh:severity to layer criticality
✓ Keep shapes & data graphs separate
✓ Validate early in your CI/CD pipeline
✗ Avoid sh:closed in open-world data
✗ Don't skip sh:ignoredProperties
  with sh:closed (rdf:type needed!)
✓ Run OWL reasoner FIRST, then SHACL