semudate-samt how to align media metadata schemas, design and implementation of the media ontology

ELIS – Multimedia Lab

How to Align Media Metadata Schemas?

Design and Implementation of the Media Ontology

Florian Stegmaier, Werner Bailer, Tobias Bürger, Mario Döller, Martin Höffernig, Wonsuk Lee,

Véronique Malaisé, Chris Poppe,Raphaël Troncy, Harald Kosch and Rik Van de

Walle


Context

How to Align Media Metadata Schemas? Chris Poppe

December 2nd 2009, SeMuDate09, Graz, Austria

Interoperability issues

EXIF

MPEG-7

DC


W3C Media Annotations Working Group

• http://www.w3.org/2008/WebVideo/Annotations/ • Mission

– Ontology• common set of properties (currently 28) describing

basic metadata for media resources– identifier, title, language, creator, creation date,

description, genre, rating, collection, copyright, target audience, frame size, sampling rate, bit rate,…

• mappings of existing formats to core ontology

– API• access to the metadata

– e.g., getValues(“creator”)




W3C Media Annotations Working Group

• Mappings currently represented by mapping table http://www.w3.org/2008/WebVideo/Annotations/drafts/ontology10/WD/mapping_table.htm



MAWG property

Relation EBUCore How to do the mapping

Datatype

XPath

ma:identifier

exact dc:identifier string EBUCoreMain/ coreMetadata/ identifier/ dc:identifier


MA Ontology

Mapping of Metadata Standards



MA properties

API (Web Interface Definition Language)

MPEG-7 Dublin Core

EBUCORE

EXIF…MEDIARDF

MA mapping (expressed as mapping table)

This paper compares different ways of implementing the MA mapping using semantic web technologies


Implementation approaches

• Two types– expressing mappings using semantic web

language• SKOS• OWL and SWRL

– expressing mappings through pivot upper ontology

• format independent ontology• format dependent ontology

• Compared on simple and complex mapping– ma:title– ma:frameSize




• Use SKOS constructs to relate properties

• Simple• Vocabularies need to be available in RDF• Some mappings/conversions can not be expressed

SKOS:Collection

Mappings in SKOS



ma:titledc:title

ma:frameSizeEbucore:formatHei

ght

Ebucore:formatWidth

SKOS:exactMatch

SKOS:closeMatch


Mappings in OWL and SWRL

• Use OWL constructs to relate OWL concepts in each ontology

• Assume OWL ontologies are available for each metadata format



OWL:equivalentProperty

ma:MediaResource

dc:title ma:title



• Use rules (Semantic Web Rule Language) to define complex mappings

• Semantic and syntactic conversions



ma:frameSize_1

ebu:formatWidth_1

ebu:ResourceManifestation_1

Unit“pixels

”

Value352

RULE

ma:width

352

ma:height

288

ma:MediaResource_1

ebu:formatHeight_1

Unit“pixels

”

Value352



• Benefits– rules allow to do conversions of values e.g.,

summing integers, concatenating strings• Drawbacks

– might be complex to express all mappings




Format Independent Ontology

• Use a generic upper ontology describing metadata• Map format-specific ontologies to the upper ontology

– mappings between the format-specific ontologies can be automatically inferred

• Consider the MA ontology as format-specific ontology• Generic metadata ontology (MEON):

– allows to describe metadata• Concept, AtomicConcept, CompoundConcept

– allows to describe relations between metadata elements• defines, contains

– includes a set of generic concepts for media resources• mainTitle, resolution, lines, columns, …




MeonOntology




containscc1

resolutionlines columns

AtomicConcept

CompoundConcept

Concept

instanceOfinstanceOf

defines

definesdefines defines



• MEON is central point to map metadata formats on each other

• Format-specific ontologies– metadata formats described using MEON

• Concept, AtomicConcept, CompoundConcept, defines, contains

– mapped to generic media concepts of MEON through relation (modeled as a Class)

• qualifies the relation (e.g., exact, more specific)• describes the mapping (e.g., hold functions for datatype

conversion)




EBUCORE Ontology

MeonOntology




cc1

MA Ontology

ma:frameSize

ebu:formatHeight1

ebu:formatWidth1

resolution lines columns

relation relationrelation


Format Dependent Metadata Ontology

• Ontology describes and relates elements of the metadata formats and the MA ontology– MA properties

• described by MAWGMetadataProperty Class

– metadata formats properties• described by StandardMetadataProperty Class

– mappings• described by MetadataPropertyRelation Class

– holds transformation rule– describes type of mapping– identifies compound relations




Format Dependent Metadata Ontology



MAWGMetadataProperty_01

MAWGMetadataProperty

StandardMetadataProperty

MetadataPropertyRelation

propertyName

“ma:title”

StandardMetadataProperty_01

propertyName

“dc:title”

metadataName“http: // purl . org /dc/ elements

/1.1/”

MetadataPropertyRelation_01

relationSemantic

“exact”


Conclusions

• No clear winner– suggestions are welcome!

• Media ontology (including mappings) and API are work in progress– feedback is welcome!



SKOS OWL + SWRL

MEON Ontology

Format dependent Ontology

Complexity + + - +

Scalability - - + -

Reasoning - + + -


Questions?



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