We examine semantic interoperability problems in the fixed income securities industry and propose a knowledge representation architecture for context interchange mediation to support dynamic integration of autonomous database, web, and procedural sources of information. For sources and receivers sharing a common subject domain, the mediator's reasoning engine can devise query plans integrating multiple sources and resolving semantic heterogeneity. Receiver applications can obtain the data they need in the form they need it without imposing changes on sources. The architecture includes: 1) data models for each source and receiver, 2) subject ontologies, containing abstract subject matter conceptualizations that would be known to experienced practitioners in the industry, and 3) context models for each source and receiver that explain how each data model implements the abstract concepts from a subject ontology