Many distributed data and knowledge base applications call for a structured approach to collaborative construction of large ontologies (conceptualizations of objects, properties, and relationships between objects of interest in specific domains). This high risk, potentially high impact research is aimed at addressing the need of such applications for ontology languages, distributed reasoning algorithms, and software tools that support rapid collaborative assembly and use of complex ontologies through partial and selective reuse of independently created ontology modules. A family of description logics (DL) based modular ontology languages, namely Package-Based Description logics (P-DL) being developed by the researchers to explore the language features, syntax, and semantics of package-based partial order ontologies (PPO). The resulting tools will be evaluated in the context of collaborative construction of animal trait (phenotype) ontologies needed for comparative genomics. Anticipated results of the research include open source software for rapid, collaborative construction of PPO (and eventually, P-DL ontologies). The resulting tools can potentially transform distributed data and knowledge base applications in the same way in which the World-Wide Web transformed the construction, sharing and use of hyperlinked documents and Wiki has transformed encyclopedia construction. Broader impacts of this research include enhanced opportunities for research-based training of graduate and undergraduate students, enhanced interdisciplinary collaborations, increased participation of under-represented groups, and engagement of the broader scientific community in developing and using increasingly sophisticated collaborative ontology development tools. The project Web site provides access to the information on the project, publications and prototype software tools.