Manfred Reichert (University of Ulm, Germany) and Marlon Dumas (University of Tartu, Estonia) have edited a special issue of the Data & Knowledge Engineering Journal (Volume 68, Issue 9). This special issue gathers extended versions of papers presented at the Sixth International Conference on Business Process Management (BPM 2008), held in Milan, Italy, September 2-4, 2008. Manfred Reichert and Marlon Dumas were also PC chairs of this conference. BPM'08 proceedings were published by Springer in its LNCS series. Over the years, the BPM conference series has grown from a rather small gathering of 80-100 specialists, to a premier forum that attracts over 200 participants and covers a range of BPM topics covering the entire lifecycle of business processes.

This special issue covers the following areas of business processes: semantics and analysis of process models, process simulation, and process execution. In the first paper, "Process Instantiation", Decker & Mendling examine alternative ways to define the instantiation semantics of process models, particularly in the context of languages in which the models may have multiple start events. In the second paper, Vanhatalo et al. define a canonical representation of process models, namely the "Refined Process Structure Tree" (RPST). The RPST of a process model is a hierarchy of sub-processes, each with a single entry and a single exit point. The third paper, "Deciding Service Composition and Substitutability Using Extended Operating Guidelines" by Stahl and Wolf, investigates open issues in the field of service protocol analysis. Next, Rozinat et al. propose an integrated approach that seamlessly links workflow execution with workflow simulation. In the final paper, "RESTful Web Service Composition with BPEL for REST'', the author proposes an extension of the BPEL standard in order to support the composition of RESTful Web services.