Resource-oriented Client Architecture

A collection of simple recommendations for decent Web application frontends

Frequently Asked Questions


In our work, we find it’s much easier to get ideas across if they can be referred to by name (compared to other approaches) and thus be made tangible. ROCA is an attempt to provide a reference for exactly this purpose.

Why “ROCA”?

It was the most reasonable and easy-to-remember name we could come up with that also resolved to a meaningful acronym.

Does ROCA intend to replace other concepts?

Not at all. ROCA builds upon well-established concepts like REST and progressive enhancement, reinforcing their importance. (Some have called ROCA “a distillation of a decade of web development experience”.)

Is ROCA the one true way?

As with every architectural choice, there are trade-offs to be made. Sometimes strict adherence to ROCA principles is not practical or sensible, so it might be judicious to consciously depart from this path for selected parts of an otherwise ROCA compliant application. Of course one should be conscious of the costs associated with such a decision - however, that’s no different from other optimizations, e.g. database normalization.

How can I install the framework?

You don’t – that’s the point. ROCA is intended to be framework-agnostic. You can pick any programming language, library, or framework, as long as you adhere to the aspects described above.

Frameworks are sometimes driven more by their authors’ personal taste, the intent to create something new, a desire to hide the Web and turn it into something different, or any combination of these factors. But even if they are totally in line with the ROCA guidelines, they can often be used in many different ways. That’s why we want to tie the whole thing more to how a Web application engineer approaches design than to any particular framework.

What are good frameworks that are a good choice for the ROCA style?

We plan to include a section on this, but would like to test the community’s reaction first. Frankly, we don’t want to risk ROCA being associated with any particular framework or even community.

But what about single-page apps? Aren’t they the future?

We don’t think so; in our view, single page apps repeat the mistakes of unnecessarily fat server-side Web frameworks on the client side. The fact that the Web relies on a series of resource representations that are linked to each other is not a bug, it’s a feature.

So you’re against dynamic pages, Ajax and stuff?

Of course not. Using JavaScript to create a better user experience is an entirely awesome idea. That doesn’t mean you have to degrade the browser into a runtime for a custom UI engine. It’s perfectly possible to use JavaScript unobtrusively, which will in our view give you the best of both worlds.

But not everything is a resource! How about dashboards, portal pages, etc.?

Yes, everything is a resource, at least if we’re talking about the Web. Because that’s the whole point of it. If it’s a dashboard we’re talking about, then the resource is the dashboard; if it’s a portal you’re looking for, you might consider that your browser already does many things one usually expects a portal to do.

Why the insistence on “static assets” - why shouldn’t the server generate JavaScript or CSS dynamically?

Externalizing CSS and JavaScript code rather than inlining it in HTML has been accepted consensus for quite a while now. Not only does this provide performance benefits, it also encourages reusability and ensures separation of concerns, thus improving maintainability.

Many of these benefits are lost when state is injected into CSS or JavaScript. In particular, cacheability is reduced and maintainability suffers due to functionality being spread across the code base (not to mention the potential for subtle bugs due to the need for escaping injected values).

For example, instead of something like this:

// HTML template
<script>var ROOT = "<? echo $root_url ?>";</script>

// JavaScript
var uri = ROOT + path;

… we prefer this:

<a href="<? $root_url ?>" id="root-url">Home</a>

var uri = document.getElementById("root-url").getAttribute("href");

Is it either 100% ROCA compliance or nothing?

Of course not. The whole point of this site, though, is to give a reference that one can compare design decisions to.

All this talk about unobtrusiveness, and then you end up using Disqus?

You’re right, Disqus violates ROCA – which is really sad. It would probably not be too hard for them to simply offer a link to the discussion itself that would allow users who don’t have JavaScript enabled to simply go to their site directly. Maybe we’ll end up building something using their REST API, but for now, we simply chose to accept it.

Who’s behind ROCA?

The ROCA style itself is nothing new and can be seen in the wild in any number of Web applications. The name and this document have been created by Till Schulte-Coerne, Stefan Tilkov, Robert Glaser, Phillip Ghadir and Josh Graham, with lots of valuable input from a number of other folks, most notably from internal discussions at innoQ as well as a presentation on ROCA at SpeakerConf 2012.

How can I use this document?

This document is licensed under a Creative Commons license, i.e. you can essentially use it as you see fit, as long as you include proper attribution and share your modifications under the same license. We explicitly encourage you to recommend, compare or develop frameworks according to this style, and intend to be as open as reasonably possible while maintaining conceptual integrity.

Can I provide feedback?

Of course, please use the issue tracker for our Github repo to share your thoughts. We welcome criticism as well as suggestions for improvement.