AT:

• Adding and deleting an identity link is logged to history (for both task and process instance identity links) as HistoricIdentityLinkLogs
• When a task is assigned to a user, a historic identity link of type "ASSIGNEE" and history event type "add" is created
• When a task is un-assigned to a user, a historic identity link of type "ASSIGNEE" and history event type "delete" is created
• When a task is set as the owner of a user, a historic identity link of type "OWNER" and history event type "add" is created
• When a user is unset as the owner of a task, a historic identity link of type "OWNER" and history event type "delete" is created
• I can query for HistoricIndentityLogs using the history service
• When performing a historic task query I can restrict on the historic identity links of any type (.taskInvolvedUser(...) and .taskInvolvedGroup()). This will return all the tasks for which an identity link pointing to that user id / group id exists
• When performing a historic task query I can restrict on the historic identity of type "candidate" links (.taskHadCandidateUser(...) and .taskHadCandidateGroup())

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OLD DESCRIPTION

We are currently migrating our Activiti Engine to the Camunda Engine.

But Camunda misses an essential Activiti-feature we are using.
In Activiti 5.16+ we were able to get call the method .taskInvoledUser() on an HistoricTaskInstanceQuery. In Camunda we can call it on TaskQuery only.
(Since 5.17 Activiti moved this method to the superclass TaskInfoQuery)
http://activiti.org/javadocs/org/activiti/engine/task/TaskInfoQuery.html#taskInvolvedUser(java.lang.String)

Before we can switch to Camunda completly and start getting enterprise support we need to get the information Activiti provides us with this method.