Selected quotes on REST and empty window interfaces

Joe Gregorio

The impetus for this post in part comes from a conversation I had at PyCon. A developer had admitted that in the past he had served up a high-traffic web page that was the same for every visitor, but then used a bit of Javascript to pull up the users information separately to customize the page, but he felt "dirty" doing it. That was pretty surprising to me because it's a perfect use of Javascript, and it highlights a misunderstanding about the role of Javascript in the web.

Sean McGrath:

I don't know which way it will go but I would suggest that if we are searching for what exactly the web *is* we have to go further than say it is HTML, as Hugh does in this piece.

For me, the web is URIs, a standard set of verbs and a standardized EVAL function. The verbs are mostly GET and POST and the standardized EVAL function is the concept of a browser that can EVAL HTML and can eval JavaScript. I don't thing we can afford to leave JavaScript out of the top level definition of what the Web is because there is too much at stake.

The short answer is that using Javascript can be RESTful:

Fielding Dissertation - Section 5.1.7:

The final addition to our constraint set for REST comes from the code-on-demand style of Section 3.5.3 (Figure 5-8). REST allows client functionality to be extended by downloading and executing code in the form of applets or scripts. This simplifies clients by reducing the number of features required to be pre-implemented. Allowing features to be downloaded after deployment improves system extensibility. However, it also reduces visibility, and thus is only an optional constraint within REST.

The emphasis is my own, and is the crux of the problem, that using too much Javascript can reduce visibility, not only to intermediaries, but also to other denizens of the web, like crawlers.

There is a broad range on which Javascript can be applied in building a web site, from sites that use HTML and CSS only, to sites that require Javascript to access any functionality. The latter are what I call "empty window" interfaces, because if you visit the site with Javascript turned off all you're going to see is an "empty window".

GWT and Search Engine indexing:

You're barking up the wrong tree here. GWT is for writing AJAX/RIA/whatever-you-want-to-call-them applications. It makes the obnoxious JS bits tolerable. JS applications are inherently unfriendly to search engines. You can overcome that (as Ian has done) but it isn't going to be as simple as tossing an HTML file on some random web server and having it indexed.

It's picking the right range for your application to sit in that matters, and picking that range depends on how searchable you want to be.

Simon Willison:

Annoyed at Google Moderator - I can see absolutely no reason why it should be a JavaScript-required service

NIST is assembling standards around SaaS, and one component of that standard is understanding the value of the data versus the risk of it being exposed. We need a similar decision framework for web applications, but in this case the reverse, the value of the data versus the risk of it not being indexed.

We do the same thing in our project -- serve up a standard page for everyone, then pull up customized code for the user. In some cases it is not just personalization but, say, a bit of content that was changed by a user action and needs to be refreshed (w/o wanting to re-render the entire page).

Whenever it IS possible, I try to follow the HATEOS principle of REST and not let javascript construct the URL, but rather have the target URL sit in a link element on the page. The link@rel lets the javascript find the proper link and send off the request. If I am not mistaken, that would help for search optimization as well. As long as the content is "surfaced," in this case by a link on the page, I assume the crawler can get to it.

And while it's often not possible, I'd like to see more folks embed link@rel=alternate in their web pages that points to a more highly structure "version" of the content/data there. My preference is Atom, but I suspect RDF would be fine for that as well. Nicely illustrated by

Posted by Peter Keane on 2009-05-08

My current thinking is that when you create a full-blown AJAX (including GWT) app, you need a "mobile"/simple version anyway.

Using rel=canonical, the AJAX pages could simply point to the mobile version of the page in question, which uses HTML only and is thus crawlable.

Posted by Manuel Simoni on 2009-05-08

@Peter Keane: if that JavaScript was delivered the server in question, then there's no violation of URI opacity, nor of HATEOAS, and the situation is no different than if you were fabricating a URI from a URI template downloaded from the server. Still, it is, of course, better to have proper links if possible.

Posted by Keith Gaughan on 2009-05-08

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