The "Semantic Market Monitoring" (SEMAMO) project is intended to provide a flexible empirical instrument for the permanent collection of data -- notably, prices -- about products and services on offeneric online market observatory, SEMAMO capitalizes on a uniform data processing scheme covering all stages from automatic data capture using configurable mediators, through integration of Web-extracted data from multiple sources and their long-term storage in a persistent econometric database, up to statistical analyses feeding into flexible reporting functions. Based on a self-contained specification framework describing formally, by means of explicit models capturing market semantics, the online markets to be tracked, SEMAMO economizes the derivation of individual market monitoring applications. During run-time, a SEMAMO instance then seeks to adaptively optimize data quality and observation e±ciency based on both, previously gathered market evidence and customer-defined reporting requirements. The framework is evaluated experimentally in a practical application to online tourism.