Workflow validation reference

Last updated: October 14, 2026Applies to current supported NIM releases

Workflows · Reference

Find the meaning and the fix for every finding the workflow designer and the configuration screen report.

NIM validates a workflow in two places:

• In the designer, with Workflow → Validate: the drawing and its soundness. See Workflow definitions.
• On the configuration's Validation tab: everything the configuration adds. See Workflow configurations.

In the messages below, X and Y stand for the names NIM fills in.

Drawing findings

The designer reports these when it cannot turn the drawing into a runnable process. Errors keep NIM from updating the generated process on save; the drawing itself is still saved. Warnings are informational.

Flows

Show findings and fixes

Finding	Severity	Meaning and fix
Sequence flow X is not attached to a shape on one side.	Error	Connect both ends of the line to a shape.
…attaches to a shape that is not a BPMN flow node.	Error	A line ends on a decoration (icon, line, or text). Connect it to a task, event, or gateway.
…needs exactly one arrow head; the arrow defines the flow direction.	Error	Give the line one arrowhead, at the end it flows to.
…connects X to itself.	Error	Remove the line. To repeat a step, loop back through an exclusive gateway.
…runs into a start event / runs into a boundary event / runs out of an end event.	Error	A start event and a boundary event have no incoming line, and an end event has no outgoing line. Reconnect the line.
…duplicates an existing flow; it is merged.	Warning	Remove the duplicate line.
The … has no incoming/outgoing sequence flow.	Error	Connect the element. A boundary event needs an outgoing line for its exception path.

Tasks, events, and gateways

Show findings and fixes

Finding	Severity	Meaning and fix
N workflow shapes are labeled 'X'; workflow labels must be unique.	Error	Give each task, event, and gateway its own label.
The start event … must have exactly one [outgoing flow]. Add a gateway to branch.	Error	Start with one line, then branch with a gateway.
The end event … must have exactly one [incoming flow]. Add a gateway to merge, or use one end event per branch.	Error	Merge with a gateway, or give each branch its own end event.
…a task takes exactly one of each. Add an explicit gateway to branch or merge.	Error	A task has one incoming and one outgoing line. Use gateways to branch and merge.
…model the join and the split as two separate gateways.	Error	A gateway either merges or splits. Draw two gateways.
…has one incoming and one outgoing sequence flow, so it decides nothing; it is mapped as a pass-through.	Warning	Remove the gateway, or add the missing branch.
…an event gateway only offers a choice, it cannot merge.	Error	Merge with an exclusive gateway.
A branch of the … runs into …; every branch must start with a timer or message event.	Error	Start each branch of an event gateway with a timer event or a message event.
The process has no start event / has N start events.	Error	Draw exactly one start event.
The process has no end event; it can never complete.	Error	End every path with an end event.

Boundary events

Show findings and fixes

Finding	Severity	Meaning and fix
The … is not attached to an activity.	Error	Add boundary events with right-click → Boundary event on a task.
…a boundary event can only be attached to a task.	Error	Attach it to a user task or service task.
…is attached to X, which is a branch of event gateway Y.	Error	The branches of an event gateway already compete. Remove the boundary event, or move the task after the event.
…is attached to service task X, which the nim service runs to completion, so the event can never occur.	Warning	Remove the boundary event, or put it on a user task.
X has N non-interrupting boundary events; it can have at most one.	Error	Keep one non-interrupting boundary event per task.

Participants and meanings

Show findings and fixes

Finding	Severity	Meaning and fix
Shape X names the participant 'P', but it is …	Warning	Only user tasks, send tasks, and message events have a participant. Clear it on other elements.
The line(s) leaving X state(s) a meaning, but only a branch of an exclusive gateway is an outcome somebody chooses.	Warning	Set meaning to none on lines that do not leave an exclusive gateway or a cancelling join.
N branches of gateway X are stated to be the positive/negative outcome.	Error	Mark only one line positive and one line negative per gateway.

Cancelling join

Show findings and fixes

Finding	Severity	Meaning and fix
…needs at least two incoming flows, and exactly two outgoing ones: one stated positive, one stated negative.	Error	Lead every branch of the parallel gateway into the join, and give it two outgoing lines.
…needs one outgoing line stated to mean positive … and one stated to mean negative.	Error	Set meaning on both outgoing lines.
No line running into the … is stated to mean negative, so no branch can cancel the others.	Error	Set meaning to negative on the refusal lines, or use a parallel gateway to merge.
The branches running into the … do not all come from one parallel gateway.	Error	A cancelling join merges the branches of exactly one parallel gateway.
…merges the branches of parallel gateway X, which another cancelling join already merges.	Error	Use one cancelling join per parallel gateway.
A branch … holds a second parallel gateway / another cancelling join / a non-interrupting boundary event.	Error	Keep each branch between the fork and the join to a single path.
A branch … runs into end event X instead / loops back / never reaches the join.	Error	Every branch must end in the join.
X lies on a branch … but is also reached from outside that branch.	Error	Nothing may enter a branch from outside.
Two branches … run through the same sequence flow.	Error	Keep the branches apart.

Soundness findings

When the drawing has no errors, the designer explores every state the process can reach. These findings mean a real case could get stuck, so fix them before you publish a configuration. The messages name the lines (places) and steps (tasks) involved.

Show soundness findings and fixes

Finding	Meaning and fix
The net can reach a deadlock: no task is enabled while the workflow is not completed …	A case can stop for good. Typically, a parallel join waits for a branch that an exclusive gateway never took. Merge alternative branches with an exclusive gateway and parallel branches with a parallel gateway.
Place 'X' can hold more than one token at the same time …	Two parallel branches meet where only one was expected, typically a parallel split merged with an exclusive gateway. Merge them with a parallel gateway.
The net is unbounded: tokens can accumulate without limit on place 'X'.	A loop keeps creating parallel work. Close the loop through an exclusive gateway.
The workflow can terminate with a token stranded on non-end place 'X'.	A case can end while a branch is still running. Merge the branches before the end event, or end each branch separately.
The net can reach a state from which completion is no longer reachable (livelock) …	A loop can never be left. Give the loop a branch that leads to an end event.
Task 'X' can never fire in any reachable execution.	The step is unreachable. Check the gateways before it.
Analysis stopped after exploring N markings; soundness could not be proven. (warning)	The process is too large to check completely. Simplify it, or test it carefully with Simulate.

Configuration findings

The Validation tab of a configuration lists these findings. Errors block saving and publishing. Warnings block publishing only. The two advisories (a send task without a template, and a duplicate display name) block nothing. Select a finding to jump to the tab where you fix it.

Configuration and definition

Show findings and fixes

Finding	Severity	Meaning and fix
The configuration has no name / starts or ends with a space.	Error	Rename the configuration.
Configuration 'C' belongs to diagram 'D' …, not to …	Error	The configuration was made for another definition. Create a new configuration for this definition.
The workflow has structurally changed since it was configured; check the configuration and save it again.	Warning	Check each step, then save.
This element is configured twice.	Error	Remove the duplicate entry.
The configured element is not a step of this workflow (any more); remove the entry.	Error	The step was removed from the drawing. Remove its configuration.

Apps and mappings

Show findings and fixes

Finding	Severity	Meaning and fix
Only a user task is performed in an app, and only the start event is started from one.	Error	Remove the App from this element.
The variable mappings have no app to map onto.	Error	Choose an App, or remove the mappings.
This user task has no app, and no gateway with labeled branches follows it …	Warning	Choose an App, or label the lines of the gateway after it, so a task list can decide the step.
The start form is where the case begins, so there is no case to fill it from yet.	Error	Remove the prefill on the start event.
Only the start takes in the session variables of whoever starts the case.	Error	Remove the session mappings from the step.
'X' is not a session variable of this nim service.	Error	Use a session variable defined under Configuration → Variables → Session.
Case variable 'v' is a … and session variable 's' a …	Warning	Align the types, or accept the conversion.
A prefill/result/session mapping is missing its case/app/session variable.	Error	Complete or remove the mapping.
'v' is not a case variable of this workflow.	Error	Declare the variable, or map to an existing one.
Two prefill/result/session mappings write 'X'.	Error	Keep one mapping per variable.
This step has to be performed in its app, but it has none.	Error	Choose an App, or clear Must be performed in its app.
App 'A' does not exist (any more).	Error	Choose another App.
App 'A' has no variable 'X'.	Error	Remove the mapping, or add the variable to the App.
App 'A' neither fills nor takes any variable …	Warning	Add variables to the App if the step must exchange data.
'X' of app 'A' cannot be taken into the case: …	Error	Use another App variable.
App 'A' fills 'X' itself; to give it a value when the step opens, make it an input variable of the app.	Error	Change the App variable's type to input.
App 'A' never fills 'X', so there is nothing to take back from it.	Error	Remove the result mapping.
Case variable 'v' is a … and 'X' of app 'A' a …	Warning	Align the types, or accept the conversion.
App 'A' cannot be performed without a value for its input variable 'p' …	Error	Prefill the required input variable from a case variable.
…and case variable 'v' it is filled from is filled by nothing.	Error	Make an earlier step or the start fill the case variable.

Service tasks

Show findings and fixes

Finding	Severity	Meaning and fix
Only a service task is performed by the nim service; this element is not one.	Error	Remove the actions from this element.
A workflow step cannot run a '…' action.	Error	Use a target system function, script function, or service resource command.
Action '…' does not say what to run.	Warning	Complete the action.
Action '…' is given / hands back 'v', which is not a case variable of this workflow.	Error	Declare the variable, or change the binding.
This service task has no actions.	Warning	Add an action, or remove the service task from the drawing.

Participants

Show findings and fixes

Finding	Severity	Meaning and fix
Participant 'P' is not bound to any user or group …	Warning	Bind the participant on the Participants tab.
Participant 'P' is bound to …, but no step of the drawing is performed by that participant.	Warning	Clear the binding.
Participant 'P' is bound twice.	Error	Keep one binding.
Participant 'P' is bound to something it cannot stand for: …	Error	Remove the invalid user or group.
Participant 'P' is resolved as '…', which the runtime cannot do yet.	Error	Use Bound here, From a case variable, or By rules.
Participant 'P' is resolved by the engine itself, so the … user(s) or group(s) bound to it are ignored.	Warning	Clear the users and groups of Initiator.
Participant 'P' is looked up from a case variable, but none is named / from 'v', which is not a case variable.	Error	Choose a declared case variable.
Participant 'P' is looked up from 'v', which is neither a number nor a text.	Error	Use a number or string variable.
Participant 'P' is looked up from 'v', but no service task fills that variable …	Warning	Fill the variable with a service task or a session mapping on the start event.
'v' says who participant 'P' is, and this step takes it from the app …	Error	Remove the App mapping. Only a service task or a session mapping may fill it.
Participant 'P' is looked up from a case variable while the case runs, so the … user(s) or group(s) bound to it are ignored …	Warning	The users and groups act as the fallback only. Informational.
Participant 'P' is chosen by rules, but there are none.	Warning	Add rules.
The condition of rule N of participant 'P' cannot be used: …	Error	Correct the rule's condition.
Rule N … has no condition and is not the fallback.	Error	Give the rule a condition, or make it the otherwise rule.
Rule N … names no user or group.	Error	Add users or groups to the rule.
The fallback rule N … cannot carry a condition / Participant 'P' has N fallback rules.	Error	Keep one otherwise rule, without a condition.
Participant 'P' has no fallback rule ('otherwise') …	Warning	Add an otherwise rule.
Participant 'P' is chosen by rules, so the … user(s) or group(s) bound to it directly are ignored.	Warning	Informational. Clear them to tidy up.
This user task / message event / send task names no participant …	Warning	Name a participant on the element in the designer.

Send tasks and display names

Show findings and fixes

Finding	Severity	Meaning and fix
No mail template is coupled to event 'workflow-step: …', so this send task sends nothing.	Advisory	Couple a template on Events → Actions. See Workflow notifications.
End users see this configuration as '…', and '…' under the same name.	Advisory	Give the configuration its own display name.

Timers

Show findings and fixes

Finding	Severity	Meaning and fix
Only a timer event goes off at a moment; this element is not one.	Error	Remove the timer setting.
This timer event has not been told when it goes off.	Warning	Set a duration or a date variable.
The timer needs a duration of at least one minute, hour or day.	Error	Enter a duration of 1 or more.
The timer takes its moment from a case variable, but names none / 'v' is not a case variable.	Error	Choose a declared variable.
Case variable 'v' is not a date or a date-time.	Error	Use a date or date-time variable.

Variables, subject, and result

Show findings and fixes

Finding	Severity	Meaning and fix
Case variable 'v' is filled by nothing …	Warning	Tick it in a result mapping, a session mapping, or an action output, or remove it on the Variables tab.
A case variable without a name … / starts or ends with a space.	Error	Rename the variable.
Case variable 'v': names starting with 'wf' belong to the workflow itself …	Error	Rename the variable without the wf prefix.
'v' is filled by the workflow itself; a step cannot write it.	Error	Remove the mapping or action output that writes a built-in variable.
Case variable 'v' is declared more than once.	Error	Names ignore case. Remove the duplicate.
Case variable 'v' has a type a case cannot carry yet.	Error	Use string, number, boolean, date, or date-time.
The case subject / result names 'v', which is not a case variable.	Warning	Correct the placeholder.

Gateways and branches

Show findings and fixes

Finding	Severity	Meaning and fix
This element does not choose between branches, so a decision variable / condition has nothing to decide.	Error	Remove the routing setting.
'v' is not a case variable of this workflow.	Error	Choose a declared variable.
This gateway routes on the outcome of a step, but no step ends with one …	Warning	Let the step before it complete with an outcome, or configure a decision on the gateway.
App 'A' completes its step with 'o', but none of this gateway's branch labels … is that …	Warning	Relabel a line, set its meaning, or change the outcome of the action.
…N of its M branches have no text on the line / two of its branches carry the same text.	Warning or error	Label every line except at most one default line, and use distinct labels.
This gateway has both a decision variable … and conditions on its branches.	Error	Keep one way of routing.
A condition is configured on a line that is not (any more) a branch of this gateway.	Error	Remove the condition.
Branch 'b' is configured twice.	Error	Remove the duplicate.
The condition on branch 'b' cannot be used: …	Error	Correct the condition: an unknown variable, a syntax error, or values that cannot be compared.
Branch 'b' is the default branch … it cannot carry a condition / N branches … are the default branch.	Error	Keep one otherwise branch, without a condition.
Branch 'b' has no condition and is not the default branch, so no case can take it.	Warning	Give it a condition.
Branch 'b' states that it is the positive/negative outcome, but this gateway routes on …	Warning	Route on the outcome, or set the line's meaning to none.

Permissions

Show findings and fixes

Finding	Severity	Meaning and fix
Participant 'P' may not read/write case variable 'v', yet …	Warning	Grant the right on the Permissions tab, or remove the mapping.
The case subject/result names 'v', which participant(s) … may not read.	Warning	Every participant sees the subject and result. Grant read, or remove the variable from the text.
Participant 'P' holds rights on 'v', which is not a case variable of this workflow.	Warning	Remove the entry with Remove unused right(s).
Participant 'P' holds rights on 'v', but no step of the drawing is performed by that participant.	Warning	Remove the entry.
Participant 'P' has two permission entries on case variable 'v'.	Error	Keep one entry.
The rights of participant 'P' on 'v' include bits that mean nothing on case data.	Error	Use only read and write.

Related guides

• Workflow definitions — validate and simulate the drawing.
• Workflow configurations — jump from a finding to the setting that needs correction.

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