IPDL is the language that Mozilla is using to describe all the messages between processes. Invented by Chris Jones, the IPDL language makes it easier for us to write type-safe and secure code by generating a lot of the basic validation code involved with messages.
When Chris was at Mozilla Headquarters a few weeks ago, he presented a tech-talk on IPDL which has been recorded and is available for download or viewing:
In the presentation, Chris explains the motivations for IPDL, demonstrates basic usage, and answers many questions about the limitations and benefits of using IPDL. I encourage anyone who is interested in Mozilla’s Multi-Process work to watch the presentation.
There are also some IPDL protocols in the tree if you’d like to read them: see the dom/ipc directory in the Electrolysis branch.