Example use cases: Checking whether a user is signed in, for example, user_id is not blank Referencing values captured in previous workflow steps, or previous runs of the workflow such as an invoice ID Comparing the current value with a previously handled value, such as invoice_id is not the same as the last processed invoice Preventing a workflow from re-triggering when the same value already exists in the conversation history Allowing a user to re-enter the workflow after signing in or supplying a new value