Use the Optional parent option in the setup of a process reference field to limit the forms shown to users in certain situations and increase ease of data entry and integrity.
Consider the following example and its processes.
I have a "Client" process to keep track of clients and their information.
I also have "Job" process to keep track of jobs. In the "Job" process there is a process reference to the "Client" process that allows me to choose the client for the job.
Now, let's say there was an incident on the job and a worker was injured on-site. To record the data I would use my "Incident Investigation Report" process. Using the Optional parent option, and choosing "Client" as the optional parent, I can display to the user only the jobs that reference the client when a client is chosen from the "Client" field.
Below is the date entry view of the incident investigation report form. Because there is only one job pertaining to the client "RPM Software," only one job form is presented to the user, instead of all the jobs if I had not chosen a optional parent for the "Job" process reference field.
Here is the setup of the "Job" process reference field and the Optional parent chosen.