Frequently Asked Questions

• What is a workflow ? A lot of people use the word Workflow when they actually mean workflow engine. Let's talk only about workflow here. A workflow is a set of activity (or tasks, something that have to be done by somebody) organized in a graph that has one or more beginning and one or more ends. A very (very) simple workflow could be "Joe produces a web page, Pete reviews it and when he agrees, Mike publishes it on a web site". This workflow only includes human participants but most vauable workflows also include other pieces of software as participants. A workflow is also very often called a process.
• What is a workflow engine ? A workflow engine is the software program that executes a workflow. A workflow is a general description of everything that can and should occur, the workflow engine uses this description to coordinate all tasks and make sure everything really occurs as supposed to.
• What is a process description language ? A workflow can be quite complex, organizing severalt tasks, with a lot of conditions, things occuring all at the same time and involving a lot of different partners. But you have to describe your workflow to a workflow engine so that it can properly understand it and execute it later on. A process description language is a specialized language (or grammar) that helps you express your workflow in words that can be understood by you and by a workflow engine. Since XML became so popular, most recent process description languages, like XPDL, BPML or WS-BPEL, are built using XML
• Why using WS-BPEL ? The Web Service Business Process Execution Language has originally been built by Microsoft, IBM and BEA Systems which are pretty big partners. We felt that this simple fact would make it a market standard. Besides, it is a good standard. Not perfect, but pretty good. The only dark spot is the licensing that is still worrying us a bit.
• What is Twister ? Twister is a workflow engine, written in Java and supporting BPEL as a process description language. But Twister is not only a workflow engine, the solution also includes several other components that make it pretty valuable for a modern software platform in most businesses.