Joshua Taylor Discovering Simple Mappings Gregory Todd Williams 2

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• Question is for the Presentation: Joshua Taylor presents Discovering Simple Mappings Between Relational Database Schemas and Ontologies
• Question is asked by: Gregory Todd Williams
• The Question is: In section 4.1, it is stated that entities are partitioned "in the relational schema and the ontology" into four groups. However, it seems that object properties (denoted P_O) belong to groups 2-3. Is this correct? If so, can these groups accurately be called partitions? Does this diminish the claim that these partitions "limit the searching space of candidate mappings"?
• Answered by: Joshua Taylor
• Answer: While the authors' notation may be a little nonstandard, the classification in 4.1 Classifying Entity Types effects both a restriction and a partition. That the four groups are disjoint: The left factors of the products are all disjoint, and therefore the products are all disjoint. Then the products are a partitioning of some set, namely the union of the products. That this union is a subset of all simple mappings: According to Definition 3 a mapping from an entity relation to an object property is a simple mapping. However, no such mapping appears in this union of products. Checking that all of the elements of the union of products are simple mappings is trivial. Then the enumerated groups is a partitioning of a subset of all simple mappings. Except in certain pathological cases (e.g., the database contains only entity relationships and the ontology contains only classes), the union of the enumerated groups is also a proper subset of the set of simple mappings.