SPATIAL DATABASES

Inaccuracy as inconsistency. The conflicting information that arises from data inaccuracy (e.g., conflicting positional information) may be treated as inconsistency if there exists an explicit integrity constraint that reflects this kind of conflicting information. What will be treated as a problem of data inaccuracy or a problem of inconsistency is still something that needs clarification.

Space does not automatically generate attribute constraints. The spatial dimension of an object does not automatically constrain the attributes of the object or the attributes or spatial components of other objects. It should be, however, an easy way to specify spatial integrity constraints.

Partial consistency. A geometric representation can be totally or partially consistent such that queries based on spatial criteria over such representation are not necessarily inconsistent.

Spatial relations. Spatial relations are usually implicitly represented and may not need positional accuracy. So, what is inconsistency with respect to objects’ positional information may not be inconsistency with respect to spatial relations between objects.

Consistency of composite objects. Composite objects treat aggregations of objects and impose constraints with respect to their parts to enforce consistency.

Application-independent versus application-dependent integrity constraints. Application-independent integrity constraints associated with spatial primitives can be built into the system with ad-hoc implementations. Application-dependent constraints, in contrast, require facilities for the generation of code to impose the constraints.

Consistency with propagation of updates. A modification in a spatial database may cause simultaneous updates in a large number of records with consequences in the consistency of data.

Consistency at multiple representation levels. Spatial databases may need to treat different levels of detail in the spatial representation. Consistency at multiple representations needs to be based on research that goes beyond considering topological relations, to incorporate, for example, orientation and distance relations.

Consistency across heterogeneous spatial databases. Distributed and interoperating spatial information systems are not always designed under the same conceptual model, with the result that what is consistent in one database is inconsistent in another. Further studies are needed to analyze the consistent integration of data not only at the geometric but also semantic level.

Management of inconsistency tolerance. In the presence of inevitable inconsistencies in a database, it is necessary to find strategies that provide consistent answers despite the fact that the database is inconsistent with respect to a set of integrity constraints. For example, a database with conflicting positional information may still provide consistent answers with respect to topological relations.

Context dependence of integrity constraints. Some integrity constraints are associated with the computational application of particular spatial operators (e.g., area and intersection). Context may determine the integrity constraint that is required for a particular use.

Integration of solutions. Advances in modeling consistency in spatial databases, such as models of consistency at multiple representations and data integration, should be integrated to give solutions to real problems.

Efficient algorithms. The complexity of spatial data requires efficient algorithms for implementing consistency models of spatial data.

 

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