The Constraint Database Framework: Lessons Learned from CQA/CDB
نویسندگان
چکیده
This paper reflects our experience with CQA/CDB, a prototype rational linear constraint database. First, we show that the standard semantics of constraint databases lead to an anomaly when queried in the presence of missing attributes. In CQA/CDB, this anomaly is avoided by enriching the CDB relational schema, resulting in heterogenous databases. Then, we present spatial databases as a special case of heterogenous databases and extend constraint query algebras (CQAs) with two additional spatial operators, proving that the resulting language is safe for linear constraints.
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