Sequential composition of schema mappings

摘要

A method for generating a schema mapping. A provided mapping M₁₂ relates schema S₁ to schema S₂. A provided mapping M₂₃ relates schema S₂ to schema S₃. A mapping M₁₃ is generated from schema S₁ to schema S₃ as a composition of mappings M₁₂ and M₂₃. Mappings M₁₂, M₂₃, and M₁₃ are each expressed in terms of at least one second-order nested tuple-generating dependency (SO nested tgd). Mapping M₁₃ does not expressly recite any element of schema S₂. At least one schema of the schemas S₁ and S₂ may comprise at least one complex type expression nested inside another complex type expression. Mapping M₁₃ may define the composition of the mappings M₁₂ and M₂₃ with respect to a relationship semantics or a transformation semantics.