Creating a look-up script for DLP

I am brand new to DLP (have been working with SEP Antivirus so far) and have been asked to create a look-up script for DLP. I can create a script, no problem, I am just trying to figure out exactly what to script.

So far, I have some understanding of the requirements, and have been asked to read Chapter 50 of Symantec DLP 11.6 Admin Guide, called "Implementing lookup plug-ins"

I'm trying to get a feel for the inner-workings of DLP, or anything that may help in general.

Can anyone point me in the right direction.