Signature
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Query Pattern/Query Instance Pattern
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Classification
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Correlation Pattern
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Intent
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To query an already executing process instance.
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Motivation
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Based on the process status or business logic, there are requirements to query an already running process for varied information.
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Applicability
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When a query event occurs, the regular flow of the process will be interrupted and the query event subprocess will execute in parallel with the main BPMN process.
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Implementation
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We can use the event subprocess to query an existing process without even interrupting the main process, and both the main process and the query event subprocess will run in parallel. A new token is created for the query event subprocess.
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Known issues
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Making certain that the request to query a process instance must result from the process instance that it is meant for.
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Known solution
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Correlation.
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