The OSIRIS Process Support Middleware and the ISIS Process-Based Digital Library Application

This paper presents the OSIRIS middleware (Open Service Infrastructure for Reliable and Integrated process Support) which allows combining different distributed services into processes, thereby implementing flexible digital library applications. In OSIRIS, we distinguish between system services and application services. System services are used internally for coordinating the execution of processes in a distributed way, without relying on a central execution engine/scheduler. In addition, the distributed architecture of OSIRIS allows for reliable peer-to-peer process management and sophisticated failure handling according to the transactional process model and is able to balance the load among several providers of the same service. For application services, we distinguish between loosely coupled and tightly coupled services. Usually, a part of the distributed OSIRIS middleware (called OSIRIS layer) runs on each host providing application services. These application services are considered as tightly coupled since, in case information on their transactional properties like compensation or re-invocation (retriability) is available, dedicated transactional guarantees for processes can be provided. Loosely-coupled application services are those that have to be called remotely, without a local ORISIS layer available. The integration/invocation is done via WSDL for service description and SOAP for invocation. The core of OSIRIS has been developed at ETH Zürich. Currently, it is being extended (e.g., for processing continuous streams of data) jointly at UMIT and at the University of Basel. There are two versions of OSIRIS: one is implemented in C++ and runs on Microsoft platforms, the other version is implemented in Java. Second, this paper also introduces the ISIS application (Interactive SImilarity Search) that has been built on top of the OSIRIS platform. ISIS consists of a set of pre-defined processes and several application services (like feature extraction, index management, index access, relevance feedback, etc.) which are used within these processes. The paper presents how the ISIS application has been built and the application services it relies on. Finally, it also gives detailed information on how new digital library applications can be built on the basis of existing services.