Domain-specific web applications often need to integrate information from schematically heterogeneous sources that share some semantic similarities. These applications often include application widgets—where each widget may address a (potentially small) subset of the local schema. We seek to provide flexible integration where each widget may use its own “global” schema and use its own mapping to each local schema. It is possible for each such “global” schema to be mapped multiple times, in different ways, to a given local schema. Traditional information integration is too rigid to meet these requirements. Here, we define a new integration model that introduces a metamodel of small domain-specific schema fragments—called domain structures—that can be mapped to local schemas. We show how generic, polymorphic widgets can be created by writing queries against domain structures using an extended relational algebra that includes a local type operator to propagate local type names to the domain structures. By bringing the local semantics to the global level we create an integration system with local dominance where important, distinct local schema semantics are available globally.