Evolving out of theoretic and practical work, this paper presents the motivation and basic ideas for the construction and use of modular knowledge bases. The approach bears upon earlier work by the two authors done separately from each other. We introduce a model which attempts to merge two previous approaches while maintaining their benefits: Modules for logical knowledge bases, and ordered by generality domains. Central aims are reusability, restriction of memory search, and management of inconsistent (competing) knowledge within one knowledge base. We explain the model by motivational examples and discuss the formal semantics of structured, modular knowledge bases for knowledge representations that are based on logic programming.