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TMCL and OWL

Lars Marius Garshol

<larsga@bouvet.no>

2008-10-17

TMRA 2008

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RDF/TM interoperability today

• Instance data can be converted back and forth– effectively allows RDF vocabularies to be used in TMs, and vice versa

• Schemas, however, cannot be converted– must be converted manually– to do this, detailed knowledge of RDFS, OWL, and TMCL is needed– awkward and error-prone

• Schemas are needed for– documentation,– schema-driven editors,– validation,– reasoning,– etc

?

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Comparing TMCL with RDFS&OWL

• Similarities– describe correct use of vocabularies– vocabularies, not separate languages

• Differences– obviously based on different technologies (TM vs RDF)– TMCL intended for individual projects, RDFS/OWL for open semantic web– TMCL has validation semantics, while RDFS/OWL have reasoning

semantics

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Validation

Rule: Every dc:creator must be a person

dc:creator

person

tm:type-instance

QuickTime™ and a decompressor

are needed to see this picture.

dc:creator

sheep

tm:type-instance

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Reasoning

Rule: Every dc:creator must be a person

dc:creator

person

rdf:type

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are needed to see this picture.

dc:creator

sheep

rdf:type

rdf:typeowl:disjointWith

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OWL Full

OWL DL

RDFS and OWL

• Divided into four layers extending each other

• Basic RDFS features:– rdfs:Class - declares a class– rdfs:Property - declares a property– rdfs:domain - restricts type of subject– rdfs:range - restricts type of object

• Example:person rdf:type rdfs:Class .

resource rdf:type rdfs:Class .

dc:creator rdf:type rdfs:Property .

dc:creator rdfs:domain resource .

dc:creator rdfs:range person .

RDFS

OWL Lite

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TMCL

• Two parts:– declarative constraints

– TMQL-based constraints

• In addition:– CTM templates for ease of

authoring

• Basic features much as in RDFS– tmcl:topictype

– tmcl:nametype

– tmcl:occurrencetype

– tmcl:associationtype

– tmcl:roletype

c isa tmcl:roleplayer-constraint;

tmcl:card-min: 0;

tmcl:card-max: 1 .

tmcl:applies-to(tmcl:constraint-role : c, tmcl:assoctype-role : dc:creator)

tmcl:applies-to(tmcl:constraint-role : c, tmcl:roletype-role : dcc:resource)

tmcl:applies-to(tmcl:constraint-role : c, tmcl:topictype-role : resource)

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Conversion principles

• Follow instance data conversion– that is, source data valid against source schema should produce valid data

against translated schema– means schema conversion is based on RTM/TMR mappings

• Translate intent– on the level of: “every dc:creator must be a person”– ignore the reasoning/validation issue

• Aim for introspectable schemas– be reasoning-friendly in RDF where possible (e.g. avoid OWL Full)– prefer TMCL Core over TMCL Query

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OWL Full

OWL DL

RDFS

OWL Lite

TMCL Query

TMCL Core

What the conversion does

• We can convert quite a lot of RDFS/OWL to TMCL– if we restrict ourselves to TMCL Core then we can convert much less

• Reverse conversion is similar– however, some features of TMCL are hard to reproduce in RDFS/OWL

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RDF-to-TM basics

• Any rdf:Class becomes a tmcl:topictype– same for owl:Class, obviously

• Any rdf:Property becomes a statement type– the question is: which?– the RTM mapping answers this for us

• Any rdf:domain statement becomes a constraint– which type of constraint depends on the RTM mapping

• Any rdf:range statement becomes a constraint– for name types: an error– for occurrence types: a datatype constraint– for association types: as for domain

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Name type mapping

x rdf:domain y

x rtm:maps-to rtm:basename

x isa tmcl:nametype .

?c isa tmcl:topicname-constraint .

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:topictype-role : y)

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:nametype-role : x)

What kind of constraint to map to?

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Occurrence type mapping

x rdfs:domain y

x rtm:maps-to rtm:occurrence

x isa tmcl:occurrencetype .

?c isa tmcl:topicoccurrence-constraint .

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:topictype-role : y)

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:occurrencetype-role : x)

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Occurrence type (2)

x rdfs:range z

x rtm:maps-to rtm:occurrence

?c isa tmcl:occurrencedatatype-constraint

tmcl:datatype: z .

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:occurrencetype-role : x)

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Association type mapping

x rdfs:domain y

x rtm:maps-to rtm:association

x rtm:subject-role s

x isa tmcl:associationtype .

s isa tmcl:roletype .

?c isa tmcl:associationrole-constraint

tmcl:card-min: 1

tmcl:card-max: 1 .

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:assoctype-role : x)

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:roletype-role : s)

?c2 isa tmcl:roleplayer-constraint .

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : x)

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : s)

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : y)

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Association type mapping (2)

x rdfs:range z

x rtm:maps-to rtm:association

x rtm:object-role o

x isa tmcl:associationtype .

o isa tmcl:roletype .

?c isa tmcl:associationrole-constraint

tmcl:card-min: 1

tmcl:card-max: 1 .

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:assoctype-role : x)

tmcl:applies-to(tmcl:constraint-role : ?c, tmcl:roletype-role : o)

?c2 isa tmcl:roleplayer-constraint .

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : x)

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : o)

tmcl:applies-to(tmcl:constraint-role : ?c2, tmcl:assoctype-role : z)

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RTM mapping

• rdfs:subClassOf TMDM superclass-subclass associations

• rdfs:subPropertyOf TMDM superclass-subclass associations

• rdfs:label base name with the default type

• rdfs:comment occurrence of type rdfs:comment

• rdfs:seeAlso occurrence of type rdfs:seeAlso

• rdfs:isDefinedBy assoc. of type tmcl:definedBySchema

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OWL to TMCL

• Much harder, but some things are easy– owl:disjointWith -> tmcl:exclusive-instance– owl:complementOf -> tmcl:exclusive-instance– owl:equivalentClass -> subclass loop– owl:equivalentProperty -> subclass loop– cardinalities -> cardinalities– owl:InverseFunctionalProperty-> unique occurrence constraint– documentary properties -> use RTM mapping

• Some OWL, strangely, becomes input to the mapping– owl:SymmetricProperty– owl:ObjectProperty– ...

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Converts to TMCL Query

• owl:intersectionOf

• owl:unionOf

• owl:allValuesFrom

• owl:someValuesFrom

• owl:hasValue

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Documentary information

• All convertible using RTM– whether it gets picked up on the other side is not clear

• owl:DeprecatedClass

• owl:DeprecatedProperty

• owl:versionInfo

• owl:priorVersion

• owl:backwardCompatibleWith

• owl:incompatibleWith

• owl:Schema

• owl:differentFrom & owl:AllDifferent

• owl:oneOf

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Non-convertible

• owl:TransitiveProperty– no constraints, only used for reasoning– no way to reproduce this in TMCL– convert as is, to let software pick it up if supported

• owl:imports– really abstract syntax, shouldn’t be converted

• owl:OntologyProperty– no equivalent in Topic Maps

• owl:AnnotationProperty– ditto

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TMCL to RDFS/OWL

• Works much the same way, but obviously in reverse– based on the TMR mapping– no attempt made to convert TMQL constraints

• Converts to– OWL Lite, if certain features are not used– OWL DL, if exclusive-instance or abstract classes are used– OWL Full, if the tmcl:*type classes are not disjoint (and a few other cases)

• Non-convertible elements– regular expressions– subject identifier/locator constraints– scope constraints

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Basic workings

• tmcl:topictype -> owl:Class

• tmcl:nametype -> owl:DatatypeProperty

• tmcl:occurrencetype -> owl:DatatypeProperty

• tmcl:associationtype -> owl:ObjectProperty

• constraints -> rdfs:range & rdfs:domain

• Abstract classes -> complicated OWL expression

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Conclusion

• Conversion between TMCL and RDFS/OWL is possible!– core of both standards convertible and roundtrippable– some limitations, however– much of OWL not convertible in introspectible fashion

• Further work– finish TMCL– implement RDFS/OWL import in Ontopoly– implement RDFS/OWL export in Ontopoly