1. Rinke Hoekstra JoostBreuker University of Amsterdam Polishing Diamonds in OWL 2

2. Overview Background Ontologies, frameworks and OWL 2 Complex concepts Exchange Limitations of OWL 2 Design pattern Discussion

3. Background ESTRELLA Legal Knowledge Interchange Format (LKIF) LKIF Core Ontology http://www.estrellaproject.org/lkif-core Not everything in OWL 2 is an ontology but Not everything that is an ontology fits OWL 2

4. Not everything in OWL is an ontology Ontology Context independent, intrinsic properties Definitions e.g. basic notions, subsumption hierarchies Framework Context dependent Dependencies, decomposition e.g. part-of hierarchies, scripts, problem solving methods, scenarios, data-structures.

5. Not everything that is an ontology fits OWL … philosophical perspective e.g. 4D ontologies Complex, structured concepts Artefacts Biological entities (e.g. organs) Exchange Physics: Heat Exchange, Balance/Equilibrium Biology: Metabolism Economy/Law: Transactions, Hohfeldian Squares (rights/duties)

6. Transaction Characteristics Reciprocity Balance Identity Problem Diamond-shape

7. OWL 2 DL Description Logics Subset of FOL, model theory Restricted Language Limited Expressiveness Decidability (sound & complete reasoning) Tree-shaped models

8. A ≡ p2some (B ⊓ p1some D) ⊓ p3some (C ⊓ p4some D)

9. Why not use rules? Superset SWRL, not decidable Subset OWL 2 RL / DLP / SROIQ Rules, decidable but inexpressive Hybrid DL-Safe rules, decidable but closed world Description Graphs (Motik, 2005) Not standard, no scalable implementation

10. Polishing Diamonds Polishing Diamonds Fine-tune the set of allowed models Approximate diamond-shaped models Patterns as Templates Emphasise a fixed structure Knowledge Patterns, Content Ontologies Design Patterns Patterns as Recipes Emphasise the design task Steps in ontology design: justification, explanation

12. Disambiguate Role Fillers Transfer ≡ actor some Agent ⊓ recipient some Agent ⊓ object some Object ⊑ actor exactly 1 Agent ⊓ recipient exactly 1 Agent ⊓ object exactly 1 Object Problem More complex: distinct properties and ranges Actor and recipient may still be the same individual Solution Assert property disjointness

13. Completion graph

14. OWL 2 DL Role inclusion axioms Traverse the tree Balance object−o part−o part o object ⊑ value_similar Identity Simulateowl:sameAs actor−o part−o part o recipient ⊑ same_id_as recipient−o part−o part o actor ⊑ same_id_as

15. Traverse the Tree (1)

16. Traverse the Tree (2)

17. Introduce Asymmetry Problem: actor and recipient are inferred to have the same identity Disambiguate branches of tree left_part & right_part Tautological Introduce domain dependence e.g. “Sales Transaction” Domain independent transaction not representable

18. Sales Transaction Goods_Transfer ⊑ Transfer ≡ object some Good ⊑ recipientg some Agent ⊓ actorg some Agent recipientg ⊑ recipient actorg ⊑ actor actor−go part−o part orecipientm ⊑ same_id_as actor−mo part−o part orecipientg ⊑ same_id_as recipient−go part−o part oactorm ⊑ same_id_as recipient−mo part−o part oactorg ⊑ same_id_as