Objects at REST...

["Andrzej Jan Taramina" <andrzej@chaeron.com>]

Rick Jeliffe just posted a blog entry entitled "Objects at REST" on xml.com, 
found here:

   http://tinyurl.com/2oqrzm

where he proposes exposing objects using REST.

I've always had a problem with this approach.  Though it seems like a good 
and easy thing to do (urlrewritefilter, which Rick mentions, does rock and 
can help clean up REST URIs nicely), but there is typically an impedence 
mismatch between objects and resources that is very difficult to bridge while 
staying true to REST principles:

1) Objects tend to be much more fine-grained than is appropriate for 
distributed systems access.  I would have thought that we would have learned 
this from the ill-fated EJB Entity beans fiasco of a number of years ago.

2) WIth objects, the tendancy will always be towards using a RPC appoach, 
which is not in keeping with REST principles.  Objects tend to have little 
"data" and many methods, while resources (in the REST sense) are the reverse, 
with much data and few methods. Mapping between the two concepts will be 
problematic.

3) It may be rare to find a clean mapping between lower level objects and 
resources, without using an intermediary facade layer to bridge the two 
levels of abstraction, especially since most OO-based systems were not 
designed to be exposed as resources using REST.

I'm curious what others think of this notion of exposing objects using REST?

I'm especially keen to see what the patriarch of REST, Roy, has to say on 
this?


Andrzej Jan Taramina
Chaeron Corporation: Enterprise System Solutions
http://www.chaeron.com