Workflow Definition
A workflow definition is a DAG with control flow nodes (start, end, decision, fork, join, kill) or action nodes (map-reduce, pig, etc.), nodes are connected by transitions arrows.
The workflow definition language is XML based and it is called hPDL (Hadoop Process Definition Language).
Oozie does not support cycles in workflow definitions, workflow definitions must be a strict DAG.
Workflow Nodes
Workflow nodes are classified in control flow nodes and action nodes:
- Control flow nodes: nodes that control the start and end of the workflow and workflow job execution path.
- Action nodes: nodes that trigger the execution of a computation/processing task.
Node names and transitions must be conform to the following pattern =[a-zA-Z][\-_a-zA-Z0-0]*=, of up to 20 characters long.
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Reference
https://oozie.apache.org/docs/4.0.1/WorkflowFunctionalSpec.html