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A Constraint-based Spatial Extension to SQLGabriel KuperBell Laboratories Sridhar RamaswamyBell Laboratories Kyuseok ShimBell Laboratories Jianwen SuyU C Santa BarbaraAbstractThe constraint database model provides a uniform frame-work for handling spatial and non-spatial data. We de-scribe our proposal for a query language for GISs based onthis model. Our language is called CSQL, as it is based onSQL. CSQL provides the full query capabilities of SQL onthe non-spatial part of the database while being tightly in-tegrated with the spatial part. This allows us to optimizeCSQL queries in a unied fashion, considering both the spa-tial and non-spatial attributes simultaneously. We are in theprocess of implementing a constraint database system usingCSQL as a query language, via a relational algebra CALG,and an extensible database system.1 IntroductionThe constraint database model [6] is an active area of re-search in the database community. The key notion of themodel is to generalize the notion of a tuple to a conjunctionof constraints, e.g., linear arithmetic constraints. It turnsout that the relational algebra and calculus can be natu-rally extended to such a model.The constraint database framework using linear arith-metic constraints is particularly appropriate for describingspatial data. In contrast to most of the previous models forspatial data, the constraint database model has a uniform,relational query language that handles both spatial and non-spatial data. This provides the potential for integrating spa-tial and non-spatial data. Apart from the advantages thisbrings to the user, such an integration also has the poten-tial of enabling us to use query optimization techniques ina GIS framework. The Cosmos1 project at Bell Labs wasestablished to investigate these aspects of constraint-baseddatabase systems.In this paper, we describe our proposal for a constraintquery language, called CSQL. This is a query language forspatial data based on SQL, being developed as a