Process Dictionary vs Proplist in Web Frameworks

[Ngoc Dao]

Hi,

Web frameworks are normally designed as layers (web server ->
middleware -> front controller -> controller -> action -> view ->
etc.). Data needs to be passed from one layer to another. There are 2
ways to pass:
1. Proplist (environment variables)
2. Process dictionary

The 2nd way:
* Is Simple and natural in Erlang because normally one HTTP request is
processed by one process.
* Makes application code which uses the framework appear to be clean,
because application developer does not have to manually pass an ugly
proplist arround and arround.

I want to ask about the (memory, CPU etc.) overhead of process
dictionary, compared to proplist. Which way should be used in a web
framework?

Thanks.