We investigate issues in the construction of an Active Service Integration System (ASIS). An ASIS is a mediation system that provides event-based monitoring and integration over data-intensive, networked services. We describe the design and implementation of the Paradox Active Service Integration System, which we have built as part of our dissertation work. Paradox addresses many of the fundamental issues of ASIS construction. Paradox extends database technology and previous work in data integration to handle event-based processing over autonomous, heterogeneous network services efficiently. We suggest capabilities and metadata that services may provide to aid in the active integration process.