Publisher Summary This chapter describes interactive application systems developed by the Tools & Materials (T&M) approach. Based on the T&M concept of workplace types, two important application types are introduced for expert workplaces and for functional workplaces. The solutions proposed are discussed on two levels: (1) domain concepts for cooperative work for handling mass data and for working with complex materials and (2) architectural concepts—including client–server architectures for persistence services, loading complex materials on demand, mapping options, and evolution of materials over the application life cycle—and connection to different databases. Software registry and generic persistence service are two different approaches to connect an application system to a database. When implementing a software registry or a generic persistence service, the points to be carefully considered include (1) client-server architecture, (2) identifiers, (3) technical data modeling and structural mapping, (4) evaluation and data warehousing, (5) load-on-demand, (6) transactions and locking, (7) class evolution, and (8) legacy databases. Also, real-world experiences with persistence are discussed along with some of the solutions that are implemented.