Open Source Workflow Engines Written in Java

Here's a review of Open Source Workflow Engines that are written in Java:

• Enhydra Shark Shark is completely based on standards from WfMC and OMG using XPDL as its native workflow definition format. Storage of processes and activities is done using Enhydra DODS.
• Codehaus Werkflow Werkflow is a flexible, extensible process- and state-based workflow engine. It aims to satisfy a myriad of possible workflow scenarios, from enterprise-scale business processes to small-scale user-interaction processes. Using a pluggable and layered architecture, workflows with varying semantics can easily be accomodated.
• OpenSymphony OSWorkflow What makes OSWorkflow different is that it is extremely flexible.
• jBpm JBoss jBPM is a platform for multiple process languages supporting workflow, BPM, and process orchestration. jBPM supports two process languages: jPDL and BPEL. jPDL combines human task management with workflow process constructs that can be built in Java applications. Includes also a Visual Designer for jPDL and Eclipse-based tooling for BPEL.
• wfmOpen WfMOpen is a J2EE based implementation of a workflow facility (workflow engine) as proposed by the Workflow Management Coalition (WfMC) and the Object Management Group (OMG). Workflows are specified using WfMC's XML Process Definition Language (XPDL) with some extensions.
• OFBiz Workflow Engine The Open for Business Workflow Engine is based on the WfMC and OMG spec. OFBiz Workflow Engine uses XPDL as its process definition language.
• ObjectWeb Bonita Bonita is a flexible cooperative workflow system, compliant to WfMC specifications. A comprehensive set of integrated graphical tools for performing different kind of actions such as process conception, definition, instanciation, control of processes, and interaction with the users and external applications. 100% browser-based environment with Web Services integration that uses SOAP and XML Data binding technologies in order to encapsulate existing workflow business methods and publish them as a J2EE-based web services. A Third Generation Worflow engine based in the activity anticipation model.
• Bigbross Bossa The engine is very fast and lightweight, uses a very expressive Petri net notation to define workflows, does not requires a RDBMS and is very simple to use and to integrate with java applications. Actually, it was designed to be embedded.
• Taverna The Taverna project aims to provide a language and software tools to facilitate easy use of workflow and distributed compute technology within the eScience community. Taverna is both a workflow enactor and also an editing suite.
• JFolder JFolder (formerly PowerFolder) contains features critical to many applications - including web pages, workflow, security, persistence, email, file management, and data access.
• Open Business Engine Open Business Engine is an open source Java workflow engine which supports the Workflow Management Coalition's (WfMC) workflow specifications, including interface 1, also known as XPDL, interface 2/3 known as WAPI and interface 5 for auditing. OBE provides an environment for executing activities in a controlled, centralized environment. OBE supports both synchronous and asynchronous execution of workflows. The primary OBE implementation is based on J2EE.
• OpenWFE OpenWFE is an open source java workflow engine. It features 3 components, easily scalable : an engine, a worklist and a web interface. Its workflow definition language is inspired of Scheme, a Lisp dialect, though it is expressed in XML.
• Freefluo - Freefluo is a workflow orchestration tool for web services. It can handle WSDL based web service invocation. It supports two XML workflow languages, one based on IBM's WSFL and another named XScufl. Freefluo is very flexible, at its core is a reusable orchestration framework that is not tied to any workflow language or execution architecture. Freefluo includes extension libraries that enable execution of workflows written in a subset of WSFL.
• ZBuilder - ZBuilder3 is a second generation of workflow development and management system which intends to be an open source product. It defines a set of standard JMX management interfaces for different workflow engines and their workflows. Abandoned
• Micro-Workflow - The micro-workflow framework targets developers who want to separate the control and logic aspects in their programs, thus making them flow independent. A well-factored flow independent application facilitates change because the most frequent business changes translate into process changes, thus leaving the code intact. Flow independence also fosters reuse, because domain objects make fewer assumptions about the control context in which they operate
• con:cern - con:cern is a workflow engine based on an extended case handling approach. A process is described as a set of activities with pre- and postconditions. An activity is executed when its preconditions are met. It manipulates the process item, thereby creating postconditions. The process flow is determined at run-time. This approach is superior to the conventional process flow approach.
• Twister - Twister's aim is to provide a new generation, easily integrable, B2B oriented workflow solution in Java, based on the latest specification efforts in this field. The process engine is based on the BPEL business process specifications and Web Services standards. Abandoned
• YAWL - YAWL (Yet Another Workflow Language), an open source workflow language/management system, is based on a rigorous analysis of existing workflow management systems and workflow languages. Unlike traditional systems it provides direct support for most of the workflow patterns (http://www.workflowpatterns.com). YAWL supports the control-flow perspective, the data perspective, and is able to interact with web services declared in WSDL. It is based on a distributed, web-friendly infrastructure.
• Zebra - Zebra is a workflow engine - originally developed to fill in the gaps in some commercial and open source workflow engines. The key differences between it and other workflow systems are able to model all the workflows described in workflow patterns, a GUI designer and Hibernate persistence layer.
• ActiveBPEL - ActiveBPEL engine is a robust runtime environment that is capable of executing process definitions created to the Business Process Execution Language for Web Services (BPEL4WS, or just BPEL) 1.1 specifications.
• XFlow2 - Inspired by simple workflow definition language in XFlow developed to improve its implementation. Externalized SQL in iBatis mapping files. Works as embedded workflow engine.
• Apache Agila - Agila is centered around Business Process Management, Workflow and Web Service Orchestration. It's composed of two specialized modules: Agila BPM and Agila BPEL. Agila BPM is basically handling tasks and users who have to complete these tasks. It's a very flexible and lightweight workflow component. Agila BPEL is a BPEL-compliant Web Services Orchestration solution
• Antflow - AntFlow is a tool for the automation and scheduiling of data system tasks, including those with complex dependencies and workflow logic. Antflow represents a new approach to simplifying system automation that leverages pipelines of hot folders chained together to perform a given task. Using XML, Antflow associates an automated task, such as data transfer, compression, or encryption, with a directory on the local system. Whenever a file is copied or written into the hot folder, the associated task is executed and the file is moved to the next hot folder in the pipeline for further processing.
• MidOffice BPEL Engine - MidOffice BPEL Editor (MOBE) is an open-source platform for process orchestration which executes, monitors, adjusts and terminates pre-defined processes). The platform is implemented using J2EE technologies and standards like BPEL, XML and SOAP. Abandoned
• PXE - PXE is a modular business process execution engine with support for business processes described in the OASIS Web Services Business Process Execution Language (WS-BPEL 2.0) or in the legacy vendor specification BPEL4WS 1.1. PXE consists of three key components: The process compiler converts a business process in XML form into an expression for the process virtual machine, The process virtual machine "runs" compiled processes and The framework is an abstraction layer that wraps and manages the necessary system-level services (persistence, communication) for the engine.
• Beexee - Bexee is a BPEL engine capable of executing deployed business processes described in BPEL by orchestrating existing Web Services.
• Syrup - Syrup can be used to describe the tasks, procedural steps, required input and output information and tools needed for each step in a business process. Syrup provides five basic concepts: Tasks, Links, Workflows, Workers and the WorkSpace. Syrup can overcome the von Neumann bottleneck that stops traditional software systems from scaling. It does this by strictly separating the specification, identification and execution phase of Workflows in a distributed setup. Syrup doesn't follow the more complex standards such as Wf-XML, BPML and XPDL.
• Dalma - The heart of the engine is an ability to capture the execution state of a thread and resume it later. Many applications of today need to have a part of the program that waits for other entities. . Often there are multiple conversations running concurrently. Those are what we call "workflow" applications. Today, those applications can be written, but one can't write it very productively. Dalma makes it very easy to write those workflow applications by letting you write it as an ordinary procedural program without any boilerplate.
• Pi Calculus for SOA - The first stage of this project is to provide an implementation of the W3C Web Services Choreography Description Language (WS-CDL). It provides the necessary tools to describe and police blueprints for complex distributed IT architectures as well as for describing cross domain business protocols (e.g. FIX, fpML, SWIFT, etc).
• Intalio|BPMN An Open Source project to be released in the second quarter of 2006. It will provide a complete BPMN designer as an Eclipse plug-in with standard BPEL 2.0 code generation capabilities.
• GridAnt - GridAnt is not claimed as a substitution for more sophisticated and powerful workflow engines such as BPEL4WS, XLANG and WSFL. Nevertheless, applications with simple process flows tightly integrated to work with GT3 can vastly benefit from GridAnt without having to endure any complex workflow architectures. The philosophy adopted by the GridAnt project is to use the workflow engine available with Apache Ant and develop a Grid workflow vocabulary on top of it. In other words, we provide a set of Grid tasks to be used within the Ant framework.
• Kepler Project - The Kepler project's overall goal is to produce an open-source scientific workflow system that allows scientists to design scientific workflows and execute them efficiently using emerging Grid-based approaches to distributed computation. Kepler is based on the Ptolemy II system for heterogeneous, concurrent modeling and design.
• JOpera - JOpera for Eclipse is a rapid service composition tool offering a visual language and autonomic execution platform for building distributed applications out of reusable services, which include but are not strictly limited to Web services. Due to its generality, JOpera for Eclipse has a wide range of applications: from classical Workflow Management and Business Process Automation, Enterprise application integration, to Virtual laboratories (e.g., scientific workflows, bioinformatics), Cluster and Grid computing and even Data Stream processing.
• Ode - Orchestration Director Engine - The initial source for Ode originates from the Sybase Business Process Enginge (BPE) and the PXE BPEL 2.0 engine from Intalio. ODE implements the WS-BPEL specification. The implementation will also support Message/Event to process correlation. ODE can be plugged into various service bus or component architectures like ServiceMix.
• Imixs - The project comprises a framework to create workflow systems as well as a reference implementation based on the J2EE standard. The project includes the development of a graphic editor for creation and management of workflow models based on the Eclipse framework.
• BeanFlow - A tiny library with just a few classes and only depends on commons-logging and Java 5. Uses plain Java code to do boolean logic, handle state, do looping, call functions, create objects, aggregation and composition. Based on just one single concept, joins.
• jawFlow - JawFlow is a Workflow Engine partially conformal to WfMC (www.wfmc.org) directives. It ia based on XML Process Definition Language (XPDL) and activities can be written in Java or any BSF based scripting language. JawFlow is composed of modules that are JMX Mbeans.
• uEngine - A BPM / Workflow Solution based on Web Services. Features a Process Designer, EIP, Web service tools and an OLAP based Process Analyzer.
• BpmScript - BpmScript aims to make writing Business Processes simple by handling Workflow, Web Services Orchestration and Sheduling. BpmScript has an embedded ServiceMix ESB. This allows it to take advantage of the prebuilt ServiceMix components (e.g. SOAP, FTP, Email, File, RSS, Jabber, JMS etc.)
• JaCOB - PXE's BPEL implementation relies on the JACOB framework to implement the BPEL constructs. The framework provides the mechanism necessary to deal with two key issues in implementing BPEL constructs: Persistence of execution state and Concurrency. By rolling up these concerns in the framework, the implementation of the BPEL constructs can be simpler by limiting itself to implementing the BPEL logic and not the infrastructure necessary to support it.
• Tempo - Intalio Tempo is a set of runtime components that support BPEL4People to bring workflow functionality to a BPEL engine. Tempo provides one possible User Interface for users to manage their tasks, which goes beyond the scope of BPEL4People. Tempo only provides runtime component. It does not provide tools to generate workflow processes nor does it provide forms.

Please let me know if I missed something that should be in the list.