I've followed the whole REST and RESTful Web Services hype with some interest the last few years, and genuinely like several aspects of REST:
- You can't go wrong with a KISS approach to software development.
- Most everybody is familiar with how the Web works, so exploiting that familiarity makes a lot of sense.
- The HTTP underpinnings of REST make it very well supported by a multitude of tools.
- By leveraging HTTP, REST has excellent support for intermediaries (i.e. proxies and caches) and all the cool things they can bring to the table.
On the other hand, I also have some reservations about the whole REST thing, and Mark Nottingham touched on several of these topics in his talk:
- As always, there is a lot of dogma to go around, and everybody has his own flavour. Is using this or that HTTP method in a particular way RESTful? Mark, who's obviously intimately familiar with HTTP, seems to have a much more pragmatic view on how you can or should use HTTP (i.e. listen to his comments on POST at the very end of the talk).
- HTTP is deceptively simple. The spec is BIG, and full of ambiguities. The entire first part of Mark's talk deals with this, and I would argue that most people (me included) only have a superficial familiarity with HTTP.
- Another thing I dislike about REST is that it's not generally applicable. For instance, suppose you're developing a search service, like Google (a typical text-book RESTful Web Service example). Most everybody in the REST community agrees that you should use HTTP GET for the search and encode the query in the URI: http://www.google.be/search?q=jellyfish. Imagine a similar search service that allows you to search for images that look like a given image. Logically this is completely in-line with the simple search service, but because of technical limitations of HTTP GET you're forced to implement this in a different way (WS-* is more consistently applicable this way).
For me, it's all about sane software engineering. If you have a well designed service, using established standards and conventions where relevant, people are going to be able to use your service without much problems. Things like REST and WS-* all have there place as tools in a developers toolbox, and it's up to us developers to make informed decisions on when to use what to build the best possible software we can.
