What is an externally implemented activity (external implementation) in BAW and how does an external system complete it?

Question

We want some tasks of a BPD to be worked in another application (a custom portal or a mobile app) instead of a coach. BAW has "External implementation" as an activity type. How does it work end to end and what does the external side have to call?

Answer 1

An External Implementation is an activity implementation with an input / output contract but no UI: BAW creates a task as usual (assigned to a team, visible in the task list, with due date and priority) and the process waits until an external application finishes the task through the REST API.

# 1. process app: External Implementation "Approve in Portal" with inputs (order) and outputs (decision, comment); a BPD activity uses it, assigned to team Approvers
# 2. external app - find open external tasks (as the user, or as an administrator with filterByCurrentUser=false)
PUT /rest/bpm/wle/v1/search/query?organization=byTask&run=true&size=50&condition=taskStatus%7CReceived&condition=taskActivityName%7CApprove%20in%20Portal
# 3. read the task's input data and the external activity ids
GET /rest/bpm/wle/v1/task/2078.911?parts=data      -> data.variables.order, externalActivityID, externalActivitySnapshotID
# 4. the contract (input/output schema) of the external activity, for a generic form renderer
GET /rest/bpm/wle/v1/externalactivity/60.0b902a52-8df2-44ed-85e2-04bbd980b01d/model?snapshotId=2064.abc...
# 5. claim and complete with output data
PUT /rest/bpm/wle/v1/task/2078.911?action=assign&toMe=true&parts=none
PUT /rest/bpm/wle/v1/task/2078.911?action=finish&parts=none&params={"decision":"APPROVED","comment":"ok"}
BPMCSRFToken: <token from POST /system/login>

Portal patterns: the external app polls the search, or is notified (a system-lane step that sends a message with the task id to the app, or BAI events); it presents the data in its own UI and finishes the task; the process continues immediately. Coaches and external implementations can be mixed per activity, so a mobile app can handle only the approval steps. On CP4BA the calls are the same with a Zen API key; Workplace lists the external task but cannot open it - keep such tasks in teams that do not use Workplace, or hand them to an Application Designer page.

Alternative without an external implementation: a normal coach task that your app completes through the same finish call - possible, but then Workplace users could also open the coach; the external implementation makes the contract explicit and validates the output data against it.

References

• Process REST API - task, search and externalactivity resources
• BAW documentation - external implementations