Moving towards the SWAN Collections Ontology [2]

The idea of reasoning with sequential structures in OWL-DL is appealing. However, as already mentioned, we cannot use the RDF vocabulary in OWL-DL.

Drummond et al. [1] proposed a way of representing sequential structures in OWL-DL. Analyzing the work of Hirsh & Kudenko [2] Drummond argued that "their representation requires extensive rewriting, the relation of the resulting structures to the original lists is not intuitive and, more importantly, the resulting structures grow as the square of the length of the list". Then, he describes a general list pattern, an intuitive approach related to that suggested by Hayes [3] and incorporated in the Semantic Web Best Practice Working Group’s note on n-ary relations.

The list pattern works as follow:
Each item is held in a “cell” (OWLList); each cell has 2 pointers, one to a head (hasContents - functional) and one to the tail cells (hasNext - functional); the end of the list is indicated by a terminator (EmptyList) which also serves to represent the empty list. A transitive property, isFollowedBy, as a super-property of hasNext as been defined as well. In other words the members of any list are the contents of the first element plus the contents of all of the following elements. A separate OWL vocabulary has been defined as the RDF vocabulary cannot be used in OWL-DL.

Through the transitive property followedBy it is possible to ask things like: give me all the items that are followedBy "AC" for instance and it doesn't matter what is in between the item and the sequence itself.

In Manchester Syntax:


OWLList can express:


For instance for the pattern (A*):

List_only_As --> List AND
hasContents ONLY A AND
isFollowedBy ONLY (List AND hasContents ONLY A)

Still, in OWL-DL there are a bunch of constraints that cannot be defined (and I would suggest to read the paper for the complete list).

The list ontology page.


[1] Nicholas Drummond, Alan Rector, Robert Stevens, Georgina Moulton, Matthew Horridge, Hai Wang and Julian Sedenberg (2006). Putting OWL in Order: Paterns for sequences in OWL. OWL Experiences and Directions (OWLED 2006), Athens, Georgia, USA.
[2] Hirsh, H. and D. Kudenko. Representing Sequences in Description Logics. in Fourteenth National Conference on Artificial Intelligence. 1997.
[3] Noy, N.F. and A. Rector, N-ary relations. 2004, Editors Draft, Semantic Web Best Practices Working Group, W3C.