Category Archives: JavaScript

AJAX+REST as the latest architectural mirage

If the Web wasn’t tragically amnesic, I could show you 15-year old articles explaining how XSLT was about to revolutionize Web applications. In that vision, your Web server would return an XML file with all the data; and alongside that XML, an XSLT (which describes how to transform the XML into HTML). The browser would run it on the XML data and display the resulting HTML. Voila! This was going to bring all kinds of benefits over the old server-spits-out-HTML model. The XML could be easily consumed by other applications (not just humans) and different XSLTs could be used to adapt to the various client platforms.

This hasn’t panned out. At least not in that form. Enters AJAX. The XML doc is still there, though it usually wants to be called JSON. The XSLT is now a big pile of JavaScript. That model has many advantages over the XSLT model, the first one being that you don’t have to use XSLT (and I’m talking as someone who actually enjoys XPath). It’s a lot more flexible, you can do small updates and partial page refresh, etc. But does it also maintain the architectural cleanliness of having a data API separated from the rendering logic?

Sometimes. Lori MacVittie describes that model. That’s how the cool kids do it and they make sure to repeat in every sentence that their Web app uses the same API as 3rd party apps. The Twitter web app, for example, is in this category, as Mike Loukides describes. As is Apache Orion (the diagram below comes from the Orion architecture)

That’s one model, and it is conceptually very elegant. One API, many consumers. The Web site of the service provider is just another consumer. Easy versioning. An application management dream (one API to manage, a well-defined set of operations and flows to test, trace and diagnose). From a security perspective, it offers the smallest possible attack surface. Easy interoperability between different applications consuming the same API. All goodies.

And not just theoretical goodies, there are situations where it is the right model.

And yet I am still dubious that it’s going to be the dominant model. Clients of the same service support different interaction models and it’s hard for a single API to work well for all without sprawling out of control (to the point where calling it “one API” becomes a fig leaf). But if you want to keep the API surface small, you might end up with chatty apps. Not to mention the temptation for service providers to give their software special access over those of their partners/competitors (e.g. other Twitter clients).

Take Google+. As of this writing, the web site is up and obviously very AJAX-driven. And yet the API is not available. There maybe non-technical reasons for it, but if the Google+ web site was just another consumer of the API then wouldn’t, by definition, the API already be up?

The decision of whether to expose the interface consumed by your AJAX app as an open API also has ramifications in the implementation strategy. Such an approach pretty much rules out using frameworks that integrate server-side and browser-side development and pushes you towards writing them separately (and thus controlling all the details of how they interact so that you can make sure it happens in a way that’s consumable by 3rd parties). Though the reverse is not true. You may decide that you don’t want that API exposed to 3rd parties and yet still manually define it and keep your server-side and browser-side code at arms length.

If you decide to go the “one REST API for all” route and forgo frameworks that integrate browser code and server code, how much are you leaving on the table? After all, preeminent developers love to sneer at such frameworks. But that’s a short-sighted view.

Some tennis players think of their racket as one tool. Others, who own a stringing machine, think of the frame and the string as two tools, that they expertly combine. Similarly, not all Web developers want to think of their client framework and their server framework as two tools. Using them as one, pre-assembled, tool may not provide the most optimal code, but may still be the optimal use of your development resources.

There’s a bit of Ricardian angle to this. Even if you can produce better JavaScript (by “better” I mean better suited to your need) than the framework, you have a higher Comparative Advantage in developing business logic than JavaScript so you should focus your efforts there and “import” the JavaScript from the framework (which is utterly incompetent in creating business logic).

Just like, in Ricardo’s famous example, Portugal is better off importing its cloth from England (and focusing on producing wine) even though it is, in absolute term, more able to produce cloth than England is.

Which contradicts Matt Raible’s statement that “the only people that like Ajax integrated into their web frameworks are programmers scared of JavaScript (who probably shouldn’t be developing your UI).” His characterization is sometimes correct, but not absolute as he asserts.

I wouldn’t write Google+ with ADF, but it provides benefits to large class of applications, especially internal applications. Where you’re willing to give away some design control for the benefit of faster development and better-tested JavaScript.

Then there is the orthogonal question of whether AJAX technologies are well-suited to a RESTful architecture. You may think it’s obvious, since both are natively designed for the Web. But a wine glass and a steering wheel are both natively designed for the human hand; that doesn’t make them a good pair. Here’s one way to plant doubt in your mind: if AJAX was a natural fit for REST, would we need the atrocity known as the hashbang? Would AJAX applications need to be made crawlable? Reuven Cohen asserts that “AJAX is quite possibly the worst way to consume a RESTful API”, but unfortunately he doesn’t develop the demonstration. Maybe a topic for a future post.

“Because that’s the way it’s done now” was a bad reason to transform perfectly-functional XML-RPC into “message-oriented” SOAP. It also is a bad reason for assuming that your Web application needs to be AJAX-on-REST.

I’ll leave the last word to Stefan Tilkov: “Don’t confuse integration architecture with application architecture.” His talk doesn’t focus on how to build Web UIs, but the main lesson applies. Here’s the video and here are the slides (warning: Flash and PDF, respectively, which is sadly ironic for such a good presentation about Web technology).

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Filed under API, Application Mgmt, Everything, JavaScript, Middleware, Mobile, Protocols, REST, Tech, Web services

To each decade its Web abomination

In the 1990 decade,we got the imagemap. Some people decided to build an entire Web page as a giant JPEG backed by an imagemap for links. Mercifully, those are all gone, I think.

In the 2000 decade, we got Flash. Plenty of people decided that their whole site would be a Flash application. Some of these are still around and only now realizing their error.

In the 2010 decade, we got AJAX. As could be expected, we are now seeing sites entirely build as a JavaScript application. Which is just as wrong.

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Filed under Everything, Flash, JavaScript

/me thinks Google Wave looks like IRC

If you’re not yet seasick with all the reviews of Google Wave, here are a few additional thoughts.

My mental picture for a Wave is that of an IRC channel on which each message is an edit to an XML doc. And where the IRC server (or a bot, like Zakim) keeps a log of all messages. I think it’s the use of bots in Wave as in IRC that pushed me towards this view. The character-per-character update reminded me of the arguments about the comparative values of the Unix “talk” command and IRC. And if the IRC comparison holds water, hang on for the upcoming bot wars. BTW, doesn’t this Wave Federation Protocol look like an ideal opportunity to resurrect the IRC bot attack code that leveraged server splits?

Leaving IRC aside, the other obvious lens through which to look at Wave is the good old WS/REST debate. Let’s brace ourselves for the “is Wave RESTful” analysis that are sure to follow. I’ll note, tongue in cheek, that an alternative (to XMPP) way to implement a Wave could be provided by the WS specifications currently being worked on in the W3C Web Services Resource Access working group : send a succession of WS-RT “Put” messages to a WS-Eventing event sink that, in turn, acts as an event source. Or formalize the sink/source combination more cleanly as a broker from WS-BrokeredNotification. Finally a non-management use case for these specifications! Good luck doing character-by-character updates over this, but I am not sure that this is the most fundamental part of Wave anyway (though it makes for a good demo).

Nick Gall is right to separate the “technology showcase” aspect from the “killer app” aspect. The demo is very nice but it takes more than cool technology to change years of habits and social conventions, supported by hundreds of tools. So I am not sure how much of a killer app this collaboration demo is, however nice. On the other hand, I can see how the underlying framework (or at least the techniques used to create it) could quickly spread. I need more time looking at the federation protocol to decide what I think about it. This blog entry clearly describes the three Ps (product, platform, protocol) and some of the history.

As far as how this may relate to systems management, I don’t see too much alignment from a modeling perspective. What really matters in IT models are the relationships between the entities and Wave puts a lot more focus on the content of each wave than its relationships with others. At least for now. The underlying synchronization techniques on the other hand seem more readily applicable. The Rasmussen brothers previously created Google Maps which I found very inspiring from an IT management point of view. Years later the IT management industry still hasn’t caught up with them.

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Filed under Everything, Google, JavaScript, Mashup

WSO2 Mashup Server

I see that WSO2 has just released version 1.0 of their Mashup Server. Congratulations to Jonathan and the rest of the team. I haven’t played with the earlier betas of the Mashup Server but I have read enough about it to be interested. Now that it’s been released, it might be a good time to invest a few hours to look into it (I just downloaded it and I filled a small documentation bug already). I know (and like) many of the WSO2 guys (Jonathan, but also Sanjiva and Glen) from the early days of the W3C WSDL working group. Plus, you have to give credit to a company that offers visibility on its web site not just to its board and management team but also to its engineers.

But the Mashup Server is not interesting to me just because I know some of its authors. There are tow more important reasons. One is that it is the integration product in WSO2’s portfolio that is the most different in its approach from the many integration products in Oracle Fusion Middleware. We want Oracle Enterprise Manager to do an outstanding job at managing Oracle Fusion Middleware, but we also want it to manage other integrations approaches as well (we manage Tomcat for example). At this point there is of course no market demand for managing WSO2’s Mashup Server, but from an architectural perspective it’s a good alternative to keep in mind along with the BPEL, ESB, ODI, etc that are already in heavy use. I am always interested in perspectives that help make sure that the most abstract application/service management concepts remain suitably abstracted, so learning a bit about the Mashup Server can’t hurt. I’ll know more once I’ve looked at it, but my impression is that the Mashup Server is somewhere between BPEL and Ruby on Rails (or TurboGears) in terms of declarativity and introspectability (yes I like to make up words) for management purposes.

This may well be sweet spot and it’s my second reason for being interested in the Mashup Server. I am always interested in tools that help with quick prototyping and the best tool is different for each job. The Mashup Server is pretty unique and I can imagine it being a nice tool for some management integration prototypes once the participating services have been suitably XML-ized (something that that Oracle Fusion Middleware makes easy).

Interestingly, the release of this JavaScript-based platform comes on the same day that Joe Gregorio declares JavaScript to be the new SmallTalk.

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Filed under Everything, JavaScript, Mashup, Mgmt integration, Tech, WSO2

Want to play a minesweeper game?

Since I am on a roll with off-topic posts…

I accidentally ran into some Web pages and scripts I wrote between 1994 and 1996. Mostly experiments with Web technologies that were emerging at the time. Some have pretty much disappeared (VRML), some are still pretty useful but slowly on their way out (CGI) but many of them are very prominent now. I found a bunch of Python scripts I wrote back then, some Java apps and applets and even a Minesweeper game written in JavaScript. And the impressive thing is that even though those were all pretty early technologies at the time, these programs seem to run just fine today with the latest virtual machines and interpreters for their respective languages. Kuddos to the people who have been growing these technologies while maintaining backward compatibility. Speaking of technologies that were emerging at the time and have made it big since then, all these were served from a Linux server and the Python stuff was developed on a Linux desktop (Slackware was the distribution of choice).

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Filed under Everything, Game, JavaScript, Minesweeper, Off-topic, Tech