I need help setting a constant in a process

Question

I have a process model that is running just fine. But I want to fetch the results from the PM for later use via a web API. I am new to Appian and I am having some problems: 
 1) I tried access the results of the process but could not query it out due to the process being inactive. It is a very short process model. Is there a way to access the results of a process which has terminated? 
 2) Since web calls are asynchronous I get back empty results from mapping the data outputs. So I decided to use a constant. 
 3) I've been trying to set a constant but the examples in the documentation are a bit terse. Can anyone give me better examples? 
 4) Web Services are a problem as I have custom data types and apparently webservices do not allow you to use them. 
 
 What would be a good approach to get the results from a process model so the outside users can use a simple lightweight JSON GET to retrieve the results for use in other applications.

sureshg57 · Accepted Answer

It is not necessary the constant to be a number though it is mentioned in documentation.

sureshg57 · Answer

It is little bit unclear what is your exact requirement, but form what i get you are trying to access/retrieve some values which is a result of a process that completed already. if this is the case I think best way is to persist the required data in database table and use webAPI to retrieve those data when ever webAPI is called. 
 
To answer how to update a constant it is pretty clearly given in the below documentation. 
When selecting constant in the smart service user Directory icon to select constant rather than opening up expression editor. 
(this approach is not good for this requirement as this may result in creating many version of the constant) 
 docs.appian.com/.../Update_Constant_Smart_Service.html

pedrol · Answer

Thank you that was what I needed. I think buggy documentation needs to be brought to Appian's attention.