Reuse of design rationales, while essential to long-term goals of both design rationale capture and software reuse, presents significant challenges to current technology. Organon Motives, Inc. (OMI) and Knowledge Evolution, Inc. (KEI) propose a system, MIRIAD (Models for Interoperable Rationale, Inference and Alternative Designs), for recording and managing reusable rationale in semantically structured repositories, MIRIAD builds on two ongoing research initiatives, FAMILIAR is a DDARPA/EDCS-funded system for management of design rationale being jointly developed by KEI and OMI. Ariadne is an OMI-funded framework, partially derived from DARPA-funded Open-RLF technology, for specifying heterogenous semantic model types and managing interoperation among models and related applications, MIRIAD will support codification and reuse of FAMILIAR-generated rationales, alternatives, and trade-offs in representations that are separable from underlying semantics of the system descriptions they annotate. Ariadne will beused to specify model types and framework for managing semantically related collections of FAMILIAR rationales. Repositories will interoperate with FAMILIAR inference capabilities, as well as with diverse software engineering environments. This will enable engineers to access and record rationale throughout a system's development and evolution, and to reuse rationales in a new and even unanticipated design situations.