Just to clarify how Drools Flow supports the requirements you are describing (refering to the Drools Flow documentation):
- can handle both automated and manual (GUI-based) steps within a workflow
Drools Flow uses (domain-specific) work items (Chapter 8) to interact with external systems. These could be automated services, or a human task management component (Chapter 9) for manual tasks. This human task component is fully pluggable but Drools Flow supports a WS-HumanTask implementation out of the box. Drools 5.1 will include web-based task lists, including custom task forms.
- supports long-running, asynchronous tasks
The engine allows you to start processes that can live for a long time. The process supports different kinds of wait states (work item nodes, event nodes, event wait nodes, sub-process, etc.) to model long-running processes. External tasks can be integrated synchronously or asynchronously.
- provides support for restarting workflows in the event of a server crash
The runtime state of all process instances can easily be stored in a data source by turning on persistence (Chapter 5.1). Therefore, all processes can simply be restored in the state they were in after a server crash.
- stores a full audit history of previously executed workflows
Drools Flow generates events about what is happening during the execution of your processes. By turning on audit logging (Chapter 5.3), these events can be stored in a database, providing a full audit history of whatever happened during execution.
- provides easy access to this audit history data
The history data is stored using a few simple database tables. These tables can be queried directly, or you could use it for generating custom reports (Chapter 12.1) that show the key performance indicators that are relevant for your application.
Furthermore, we believe that a knowledge-oriented approach, allowing you to seamlessly combine processes with rules and event processing whenever necessary, will offer you more power and flexibility compared to aforementioned process-oriented engines.
Kris Verlaenen
Drools Flow Lead
Best Answer
Best is to simply start with the Drools Flow manual: https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/docs/drools-flow/html/index.html
Lots of other useful information in the blog entries: http://blog.athico.com/search/label/Drools%20Flow
and some examples can be found here: http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples/drools-examples-drl/
and here as part of the unit tests (Process*Test.java): http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-compiler/src/test/java/org/drools/integrationtests/
Kris