The Open For Business Project: Workflow Engine Guide

Written By: Andy Zeneski, [email protected]
Edited by Les Austin
Last Updated: August 04, 2004

Table of Contents

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The Open for Business Workflow Engine is based on the WfMC and OMG specifications. (See the related documents for information on these specs.) The Workflow Engine is a member of the Services Framework, and is tightly integrated with the Entity Engine. It uses the entities found in entitymodel_workflow.XML for definition information and entitymode_workeffort for runtime storage. All changes to a process or activity are persisted real-time. Therefore, the engine does not run in a thread, it is simply a group of APIs and common objects which handle the flow. When a change to the workflow is made, the engine then processes that change. When finished, the engine returns. Hence, if the application does crash, or the system reboots, the workflow will continue right where it left off upon restart.

The Workflow Engine is not designed for processing flow of a web site. This is a common misconception. Web site flow is controlled by the Control Servlet. Workflow is the processing of manual and automatic activities to fulfill a specific goal.

OFBiz Workflow Engine uses XPDL as its process definition language. This is an open standard, and very flexible. In cases where the XPDL spec does not specifically state or leaves the implementation up to the vendor, we have noted them in the section "XPDL Extensions," below.

XPDL Extensions

Workflows are designed using a processes definition language called XPDL. This document does not go into detail about XPDL, that is explained in a document created by the WfMC, see related documents.

There are a number of attributes the WfMC says is left to the vendor. Here we will document our extensions: (These are implemented as 'ExtendedAttributes')







Client API

The client API for the OFBiz Workflow engine consists of a set of global services and a factory class. The factory class named org.ofbiz.workflow.WfFactory, can either create a new instance of a workflow component (process/activity/assignment) or it can locate an existing instance. Instances are stored in the WorkEffort entity and are loaded as necessary. The set of global services found in org.ofbiz.workflow.WorkflowServices are setup to make assigning, accepting and completing assignments/activities easier. It is not required to use these services, but it is highly recommended. You will want to review the JavaDocs for these classes.

The workeffort web application shows an example of a workflow web client. From this interface you can accept assignments which are currently assigned to your group/role and edit the state. Try http://localhost:8080/workeffort.

Workflow Activities

The combination of manual and automatic activities is what makes a workflow so powerful. The OFBiz Workflow Engine currently implements NO, ROUTE, TOOL:Procedure, and SUB-FLOW type activities. TOOL:Application type activities are not yet implemented but will be in a future release.

The current version of the OFBiz Workflow Engine does not implement LOOPS. These too will be added in a future release.


To use the workflow engine you must first have a process you wish to invoke. Design your process in XPDL format. Once your design is complete, import the XPDL file into the workflow entities. You can do this from the webtools web interface. After the workflow is imported it can now be made available for execution. The easiest way to invoke a workflow is to define it as a service. Create a service definition for the workflow process and set its engine-type to 'workflow'. From there you can start a workflow process just like running any other service.

Documentation Notes

We know this documentation does not go into much detail. And we apologize for that. However, we spend a most of our time writing the code base, so documentation doesn't get full attention. We realize the need for good documentation, but our resources are limited. If you or anyone you know is interested in helping The Open For Business Project by contributing time writing better documentation, please contact the e-mail address at the top of this document. Thank you.