The OASIS standard LegalRuleML (in draft) is an XML language for the machine-readable representation of rules in the legal domain. The design process of this language includes the development of a metamodel in RDFS axiomatizing the rdfs:subClassOf hierarchy of the LegalRuleML concepts and the rdfs:domain and rdfs:range of the properties used to describe the instances of these concepts. This presentation outlines the metamodel specifications and shows diagrams of the current version of the metamodel. The metamodel also provides an avenue for exposing the legal rule metadata as Linked Data in RDF.

1. LegalRuleML Metamodel
Tara Athan, Harold Boley, Guido Governatori,
Monica Palmirani, Adrian Paschke, Adam
Wyner
July 13, 2013
RuleML 2013
7th International Web Rule Symposium, Seattle

2. Contents

Purpose of Metamodel

Role of Metamodel in LegalRuleML Design
Process

Entity-Relationship Diagrams of Metamodel

3. Purpose of Metamodel

Expose LegalRuleML Metadata as Linked Data

Provide partial semantics by transformation
– LegalRuleML → RDF + RDFS (+ OWL)

Establish connections to external ontologies
– Dublin Core
– FRBR
– RDF/RDFS
– RuleML Metamodel

Essential Component of LegalRuleML's
Language Design Process

4. LegalRuleML's Cyclic Language
Design Process

Legal Source Examples

LegalRuleML Metamodel as RDFS Schema

RDF Instances based on Metamodel

LegalRuleML Instances from RDF/XML

XML Schemas Validating Against Instances

Glossary of XML Elements and Attributes

Repeat

5. LegalRuleML Metamodel as RDFS
Schema

rdfs:Class
– Names for classes of entities
• Following RDF(S) conventions, UpperCamelCase
– rdfs:subClassOf hierarchy

Connections to external ontologies

rdf:Property
– Names for dyadic relations between entities
• Following RDF(S) conventions, lowerCamelCase
– rdfs:domain, rdfs:range
– rdfs:subPropertyOf hierarchy

Connections to external ontologies

6. LegalRuleML Metamodel as
(Future) OWL Ontology

owl:sameAs
– Used in RDF instances

rdfs:comment
– Natural language definitions of classes and
properties
– Describes characteristics that are beyond RDFS
expressivity
• Property Chaining
• To be implemented

7. RDF Instances based on
Metamodel

Simplified Samples Extracted from Legal
Sources

Compactification
– Start with Unnested Triples in any RDF format
– Nest in Tree Structure using RDF/XML
abbreviations to eliminate explicit blank nodes

8. LegalRuleML Instances from
RDF/XML

Produced by semi-standardized invertible
manual transformation

Design Principles
– Striping
• Fully-striped normal form
– Alternating Node (rdfs:Class) element and
edge (rdf:Property) element
– One child per edge (except for
rdfs:Collections)
• Compact form with redundant stripes
removed (stripe-skipping)

9. LegalRuleML Design Principles
(cont.)
 Renaming - shorter element and attribute
names, still human readable

<Node>Collection → <Nodes>
 Node-skipping

Nodes always appearing as blank nodes may be
skipped provided no type information is lost
 Leaf Stripes

Nodes that often have no content may optionally
be skipped, leading to a “leaf-stripe”, provided no
type information is lost

10. LegalRuleML Design Principles
(cont.)
 Attributes versus Edges

Attributes can lead to more compact syntax

However, may inhibit extensibility

Only used if, with high confidence,
 Property will never have cardinality >1
 Object will never be a blank node
 Literal Object always has a unique specified datatype

11. XML Schemas Validating Against
Instances

Modular Relax NG schemas
 Customization by selection of a subset of the
modules
 Extension by including additional modules

Generated Monolithic XSD schemas

Schema Validation using various engines
(Saxon EE, XMLSpy, …)

Instance Validation as Requirements Testing

12. Glossary of XML Elements and
Attributes

Definitions for XML elements and attributes

Synchronization with natural language
comments in RDFS metamodel
 Initiates update of metamodel

13. Upper Metamodel (Classes)
rdf:List

14. Upper Metamodel (Properties)
rdf:List
xsd:string
xsd:any

15. Context Metamodel

16. Statement Metamodel
xsd:any
ruleml:Rule
ruleml:RuleClass

17. Defeasible Metamodel

18. Metadata Metamodel
frbr:Agent
frbr:Jurisdiction
frbr:Concept

19. Legal Temporal Metamodel

20. Deontic Metamodel
ViolationFormula