Application portals, or Problem Solving Environments (PSEs), provide user environments that simplify access and integrate various distributed computational services for scientists working on particular classes of problems. Specific application portals are typically built on common sets of core services, so reusability of these services is a key problem in PSE development. In this paper we address the reusability problem by presenting a set of core services built using the Web services model and application metadata services that can be used to build science application front ends out of these core services
