A while back I recorded my thoughts on what I called MET, or the Model Endpoint Template organizational pattern, as used in MarkLogic Application Builder. One difference between 2009 and now, though, is that browsers have distanced themselves even farther from XML, which tends to undercut the eliminate-the-impedance-mismatch argument. In particular, the forms model in HTML5 continues to prefer flat data, which to me indicates that models still play an important role in XQuery web apps.

So I envision the app lifecycle like this:

1. The browser requests a particular page, say the one that lets you configure sorting options in the app you’re building
2. An HTML page loads.
3. Client-side script requests the project state from a designated endpoint, the server transforms the XML into a flat list, and delivers it as JSON (as an optimization, the server can package the initial data into the page delivered in the prior step)
4. Standard form interaction and client-side scripting happens, including manipulation of repeating structures mediated by JavaScript
5. A standard form submit happens (possibly via script), sending a flat list back to the client, which performs an update to the stored XML.

Another thing that’s changed is the emergence of XQuery plugin technology in MarkLogic. There’s a rapidly-growing library of reusable components, initially centered around Information Studio but soon to cover more ground. This is going to have a major impact on XQuery app designs as components of the app (think visualization widgets) can be seamlessly added to apps.

Endpoints still make a ton of sense for XQuery apps, and provide the additional advantage that you now have a testable, concern-separated data layer for your app. Other apps have a clean way to interop, and even command-line operaton is possible with off-the-shelf-tools like wget.

Lastly, Templates. Even if you use plugins for the functional core of your app, there’s still a lot of boilerplate stuff you’d not want to repeat. Something like Mustache.xq is a good fit for this.

Which is all good–but is it MVC? This organizational pattern (let’s call it MET 2.0) is a lot closer to it. Does MET need a controller? Probably. (MarkLogic now ships a pretty good one called rest:rewrite) Like MVC, MET separates the important essences of your application. XQuery will never be Ruby or Java, and its frameworks will never be Rails or Spring, but rather something uniquely poised to capture the expressive power of the language to build apps on top of unstructured and big data. -m

In other words, see you all at XML Prauge 2011. I’ve never been to this conference before, and each year I hear better and better things. Looking forward to it. -m

Also of note: eRDF has dropped off the map. hAtom and hReview are continuing their climb.

-m

Let me grab a random shortened link from Twitter. Don’t go away, I’ll be right back.

http://bit.ly/b1fYi1

OK, that’s six characters in the domain, a slash, and six more characters. 50 years from now, if bit.ly is still in operation, the URLspace will be rather more crowded, and the part after the slash might be eight or nine characters. This is a significant cliff, since most people have trouble remembering more than 6 or 7 things in their head at a time. Thus, one could conclude that 50 years from now, newly minted bit.ly URLs will be less fashionable than those from newer link-shortening services, particularly if more short TLDs come online, which seems likely. In that scenario, fewer and fewer people will use bit.ly, and it will become a resource-pit as costs go up (for more database storage, among other things) while usage drops, an economic trend that has only one eventual outcome, leading to the breaking all the external links relying on this service.

I’ve been picking on bit.ly here, but the same principle applies to any shortener service. In fact, the more popular, the more quickly the URLspace will fill.

The moral: don’t use link shorteners for anything that needs to be more durable than something you’d scribble on a scrap of paper at your desk.

More collected Geek Thoughts at http://geekthoughts.info.

But with browser forms, input and output are tightly intermingled. The View takes care of input and output. Something else has primary responsibility for mediating the data flow to and from the model–and that something has been called a Presenter. This yields the MVP pattern.

The terminology gets confusing quickly, but roughly

XForms Instance == MVP Model

XForms Model == MVP Presenter

XForms User Interface == MVP View

It’s not wrong to associate XForms with MVC–the term has become so blurry that it’s easy to lump variants like MVP into the same bucket. But to the extent that it makes sense to talk about more specific patterns, maybe we should be calling the XForms design pattern MVP instead of MVC. Comments? Criticism? Fire away below. -m

Photo by Micah

I know he left many things undone, for example only enhancing 60% of the delivered result pages. He never got a chance to finish his life’s ambition of promoting RDFa and microformats to the masses or to be the killer app of the (lower-case) semantic web. You could say he will live on as “some of this structured data processing will be supported natively by the Microsoft platform”. Part of the monkey we loved will live on as enhanced results continue to flow forth from the Yahoo/Bing alliance.

The SearchMonkey Alumni group on LinkedIn is filled with wonderful mourners. Micah Alpern wrote there

I miss the team, the songs, and the aspiration to solve a hard problem. Everything else is just code.

Isaac Asimov was reported to have said “If my doctor told me I had only six minutes to live, I wouldn’t brood. I’d type a little faster.” Today we can identify with that sentiment. Keep typing.

-m

Late that night, with 15 minutes of battery remaining, I found it. The operative search term is XSLTJSON. -m

Some interesting tidbits overheard, in no particular order…

“it is not necessarily clear that this approach would capture the difference between the ridiculous and the merely implausible.”

Complexity — what is the relationship betwen complexity and long-term data storage?

“Narratives with fancy words in them”

How do you store, say, a video in a format that will be readable in 100 years?

Order of magnitude scale changes produce discontinuities

“The Da Vinci Schema”

Dandelion DNA (Free license)

“Indispensible” — “I don’t think that means what you think it does”

“Keeping electrons alive is really difficult”

“I wondered…with my Topic Map brain damage…”

-m

This pushes all of my buttons. It’s got structured documents, Web, parser geekery, writing, engineering, and standards. There’s a bunch of open source prior art, including PyXMLWiki, which I adapted from some fantastic earlier work from Rick Jelliffe.

Sadly, MarkLogic employees aren’t eligible to enter. Get your write-up done by July 15 and sent to balisage-2010-contest at marklogic dot com. The winner will be announced at Balisage and will take home some serious prize winnings, and also will be strongly encouraged (but not required) to give a brief summary (~10 minutes) of their winning entry.

Can’t wait to see what comes out of this. -m

XML, or to be really specific, XML Namespaces, comes with its own set of challenges. Making an interface that’s usable is no small task, particularly when your target audience includes the 99.9% of people that don’t completely understand namespaces. Take for example a simple step, like p:delete.

In brief, that step takes an XSLTMatchPattern, following the same rules as @match in XSLT, which ends up selecting various nodes from the document, then returns a document without any of those nodes. An XSLTMatchPattern has a few limitations, but it is a very general-purpose selection mechanism. In particular, it could reference an arbitrary number of XML Namespace prefix mappings. Behind a short string like a:b lies a much longer namespace URI mapping to each prefix.

What would an intuitive user interface look like to allow entry of these kinds of expressions? How can a user keep track of unbound prefixes and attach them properly? A data-driven approach could help, say offering a menu of existing element, attribute, or namespace names taken from a pool of existing content. But by itself this falls short in 1) richer selectors, like xhtml:p[@class = "invalid"] and 2) doesn’t help in the general case, when the nodes you’re manipulating might have come from the pipeline, not your original content. (Imagine one step in the pipeline translates your XML to XHTML followed by a delete step that cleans out some unwanted nodes).

So yeah, this seems like a Really Hard Problem, but one that’s worth taking a crack at. If this sounds like the kind of thing you’d enjoy working on, my team is hiring–drop me a note.

-m

This is what XML was supposed to be like. Now that XML has fallen off the hype cycle, we’re getting some serious work done. -m

In 2005 I called continued development of XLink a “reanimated spectre”. But even earlier, in 2002 I wrote one of the rare fiction pieces on xml.com, A Hyperlink Offering, which using the format of a Carrollian dialog between Tortoise and Achilles, explained a few of the problems with the XLink specification. It ended with this:

What if the W3C pushed for Working Groups to use a future XLink, just not XLink 1.0?

Indeed, this version has minor improvements. In particular, “simple” links are simpler now–you can drop an xlink:href attribute where you please and it’s now legit. The spec used to REQUIRE additional xlink:type=”simple” attributes all over the place. But it’s still awkward to use for multi-ended links, and now even farther away from the mainstream hyperlinking aspects of HTML5, which for all of its faults, embodies the grossly predominant description of linking on the web.

So in many ways, my longstanding disappointment with XLink is that it only ever became a tiny sliver of what it could have been. Dashed visions of Xanadu dance through my head. -m

Early bird registration ends Feb 28. -m