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Open Source Workflow Engines Written in Java » Integrating workflow engines with other system modules
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This site conforms to the following standards:
Some products are engines that can be called upon by other programs. www.skelta.com is an example of this. Another to is a full product that allows either the workflow engine to be used stand alone or for other systems to be integrated into the workflow products GUI. www.webandflo.com is an example of this
Both are not open-source. They're thus not relevant here.