14

Jan

20

08

Pete Johnston, Eduserv Foundationpete.johnston@eduserv.org.uk

www.eduserv.org.uk/foundation

Aggregation Identity and owl:sameAs

OAI ORE Technical Committee Meeting, Washington, D.C.

14 Jan 2008OAI ORE Technical Committee Meeting, Washington D.C., USA 2

Aggregation Identity & owl:sameAs

• owl:sameAs

• What do we want to say?

Title slide photo of Washington Monument by Flickr user AlbinoFlea

See http://www.flickr.com/photos/albinoflea/290380716/

Made available under CC Attribution-NonCommercial 2.0 Generic license

14 Jan 2008OAI ORE Technical Committee Meeting, Washington D.C., USA 3

owl:sameAs

• Property defined by Web Ontology Language (OWL)

• States that two URI references refer to the same thing

• Reflects the “no unique name“ assumption of the Semantic Web

– i.e. no assumption that all data creators refer to thing using one name/URI

– multiple data creators may define names/URIs for the same thing (URI Aliases)

• Widely used in “Linked Data”

14 Jan 2008OAI ORE Technical Committee Meeting, Washington D.C., USA 4

Identification v Interaction

• N.B. Dealing here with identification, not interaction• If I claim Resource:A owl:sameAs Resource:B, then

– My assertion says nothing about (set of) representation(s) for Resource:A and Resource:B available at any time

– Set of representations available for Resource:A may be quite different from set of representations for Resource:B

• And conversely… • If Resource:A and Resource:B have same set of

representations, then– That alone is not sufficient to support the conclusion

that Resource:A owl:sameAs Resource:B

14 Jan 2008OAI ORE Technical Committee Meeting, Washington D.C., USA 5

owl:sameAs and Inferences

• If – Resource:A owl:sameAs Resource:B

• Then– Resource:A Prop:P Resource:X

=> Resource:B Prop:P Resource:X– Resource:X Prop:P Resource:A

=> Resource:X Prop:P Resource:B• e.g.

– Resource:A dc:creator Person:P=> Resource:B dc:creator Person:P

– Resource:A dcterms:created “2008-01-14”=> Resource:B dcterms:created “2008-01-14”

– ReM:R ore:describes Resource:A=> ReM:R ore:describes Resource:B

14 Jan 2008OAI ORE Technical Committee Meeting, Washington D.C., USA 6

What do we want to “say”?

• If the requirement is to say “Aggregation:A and Resource:R are the same resource” (i.e. URIs are aliases, “Aggregation:A aka Resource:R”)

• Then– Use owl:sameAs– But providers must bear in mind what that means, i.e. the

inferences which follow, and make assertion only where appropriate

• If the requirement is to say “Aggregation:A and Resource:R are different resources, related in some way” (i.e. URIs are not aliases)

• Then– Need to clarify what that “related in some way” relationship is– Need to define new ORE property (or select existing property from

other vocabulary)

14

Jan

20

08

Pete Johnston, Eduserv Foundationpete.johnston@eduserv.org.uk

www.eduserv.org.uk/foundation

Aggregation Identity and owl:sameAs

OAI ORE Technical Committee Meeting, Washington, D.C.