Workflow Validation

Only valid Workflows can be used to create WorkflowRuns. In order to be valid, a Workflow must have all its elements (WorkflowJob, InputPort, OutputPort, Connection) valid, and its workflow graph valid.

1. For any WorkflowJob in the Workflow:

• it has at least one OutputPort
• the number of its InputPort and OutputPort should satisfy the requirements of InputPortType and OutputPortType of corresponding Job
• each field in its setting should satisfy the requirements of the corresponding Job

2. For any InputPort in the Workflow:

• its InputPortType must belong to the underlying Job
• it should have zero or one Connection

3. For any OutputPort in the Workflow:

• its OutputPortType must belong to the underlying Job
• there must exist a common ResourceType between this OutputPort and its connected InputPorts.

4. Finally, the workflow graph should:

• be nonempty (have at least one WorkflowJob)
• be connected, i.e., from any WorkflowJob it is possible to reach every other WorkflowJob in the Workflow (treating the Workflow's connections as undirected)
• have no cycles.

Validation Error Table

Error Code	Description	Arguments
WFJ_NO_OP	The WorkflowJob has no OutputPort.	WorkflowJob
WFJ_TOO_FEW_IP	The WorkflowJob has too few InputPorts.	WorkflowJob, InputPortType
WFJ_TOO_MANY_IP	The WorkflowJob has too many InputPorts.	WorkflowJob, InputPortType
WFJ_TOO_FEW_OP	The WorkflowJob has too few OutputPorts.	WorkflowJob, OutputPortType
WFJ_TOO_MANY_OP	The WorkflowJob has too many OutputPorts.	WorkflowJob, OutputPortType
WFJ_INVALID_SETTINGS	The WorkflowJob has invalid settings.	WorkflowJob
IP_TYPE_MISMATCH	The InputPortType of InputPort does not belong to the underlying Job of WorkflowJob.	InputPort
IP_TOO_MANY_CONNECTIONS	The InputPort has more than one connections.	InputPort
OP_TYPE_MISMATCH	The OutputPortType of OutputPort does not belong to the underlying Job of WorkflowJob.	OutputPort
RESOURCETYPE_LIST_CONFLICT	InputPort accepts a list of resources but OutputPort is not list-typed. OR OutputPort is list-typed but InputPort is not.	OutputPort, InputPort
NO_COMMON_RESOURCETYPE	There is no common ResourceType between an OutputPort and connected InputPorts.	OutputPort, InputPort1, InputPort2, ..., InputPortN
WF_EMPTY	Workflow is empty.	None
WF_NOT_CONNECTED	The Workflow is not connected.	None
WF_HAS_CYCLES	The Workflow has cycles.	Connection (that causes the problem)

Example: the server may return -

HTTP 409 CONFLICT
{
    'associated_objects': {
        'workflowjobs': ['http://testserver/workflowjob/06b056b9282f445591c6f564e09bdae2/']
    },
    'details': ['The WorkflowJob gamera.rotate has invalid settings.'],
    'error_code': 'WFJ_INVALID_SETTINGS'
}

Workflow Graph Validity Check Algorithm

Step 0 If there are no WorkflowJobs, the graph is empty. Terminate the algorithm.

Step 1 Initialize variable permanent_marks_global <- ∅ and temporary_marks_global <- ∅. Let U denotes to the universal set containing all WorkflowJobs.

Step 2 Initialize disjoint-set data structure: for every WorkflowJob as v, perform MakeSet(v).

Step 3 Perform following "integrated depth-first-search" subroutine on an arbitrary WorkflowJob in U\permanent_marks_global as w: (algorithm enhanced from cycle detection algorithm to perform connectivity check in one DFS)

• If w ∈ temporary_marks_global, the graph HAS a cycle. Raise an exception.
• If w ∉ permanent_marks_global:
  • temporary_marks_global <- temporary_marks_global ∪ {w}
  • Find all distinct WorkflowJobs whose input_ports are connected to output_ports of w, for every of them as v:
    • perform "integrated depth-first-search" subroutine on v.
    • perform Union(w, v)
  • permanent_marks_global <- permanent_marks_global ∪ {w}
  • temporary_marks_global <- temporary_marks_global - {w}

Step 4 If U\permanent_marks_global ≠ ∅, jump to Step 2

Step 5 If ∃w, v s.t., Find(w) ≠ Find(v), the graph is NOT connected. Terminate the algorithm.

Step 6 Declare that the graph is connected and has no cycles.

Examples of Workflow Validity

Example	Validity
	Not valid. The Workflow has cycles.
	Valid.
	Valid.