Category: Apache Sling

Apache Sling is a REST API that sits on top of Apache Jackrabbit.

Adobe acquires Day Software for $240 million

I’ll admit it. I did not see this one coming: Adobe announced today that it will acquire Day Software for $240 million USD. (Thanks, @pmonks, for the heads-up tweet).

Honestly, I thought Adobe would acquire Alfresco by the end of last year and I was surprised when it didn’t happen. They had done a big OEM deal making Alfresco part of LiveCycle and they did a gigantic Alfresco implementation as part of standing up Adobe’s site. Heck, Adobe even hosted Alfresco’s community event back in 2008. All small potatoes in the grand scheme of things, I know, but I can’t help but feel like the proud parent who’s daughter brought home a keeper, only to find out the guy’s been dating a hottie from Switzerland the whole time.

Day has a FAQ up on their site. As you would expect, Day promises that current customers have nothing to fear and that the products will continue to live on.

Day has some really cool stuff in both their commercial products and their open source projects (Sling, Jackrabbit). I hope the acquisition gives Day a huge injection of resources they are able to invest in the open source side of things.

Congrats to Erik Hansen, David Nuescheler, Kevin Cochrane, and the rest of the Day team!

Catching up on XForms, XRX, XProc, and Orbeon

I recently spent a little time looking at open source components we could assemble to provide a basic web form authoring solution embedded within one of our SaaS offerings. Rather than full-blown Web Content Management, all that the solution really called for was the ability for non-technical users to enter data in a form and to upload binary objects which may be related in some way to that form data. There could be several forms with some chunks of forms being reused, and at some point, it might be nice for non-technical people to create their own forms.

For the forms piece I immediately thought of XForms because (1) I knew we wanted the data stored as XML and (2) I like the MVC pattern that XForms follows.

It had been a while since I played with XForms directly. Alfresco’s web forms engine is currently based on the Chiba implementation of XForms, but you don’t normally get exposed to the XForms details. There are a few things going on in the world of XForms that caught my attention:

XProc. XProc is a W3C specification for an XML Pipeline Language. If you’ve ever worked with Apache Cocoon you’ll get this concept immediately as Cocoon was an early implementor of the XML pipeline approach. Think of raw XML going in a pipeline on one end, having it processed with one or more steps as it goes through the pipeline, and then possibly new XML emerging from the other end. Those processing steps can be thought of as modules that can be reused and recombined in different ways to build new pipelines.

One of our past clients was doing something similar to this with their own home grown solution. They were taking XML data feeds from sporting events, and then performing various operations on that XML before it was eventually posted on the web site in the form of scoreboards and stats pages. They called the process definition a “workflow” and it was described in XML. XProc would be ideal for something like that.

XRX. XRX stands for XForms/REST/XQuery. It is not a standard–it’s an approach for building web applications. It means using XForms on the front-end to present and capture data, REST between the front-end and the back-end, and XQuery to retrieve and transform XML from the back-end. This approach allows you to build a web application without any object-relational mapping. The data you are dealing with is always XML so there is no translation necessary.

eXist. eXist is an open source, native XML database. If you’re dealing exclusively in XML, why go to the trouble of translating your XML into rows and columns (and then back in to XML when it is retrieved)? Native XML databases do a better job of storing XML with no translation required while preserving your ability to efficiently do things like XQuery and XPath statements across the entire scope of your dataset. I had previously played with Apache Xindice but Xindice doesn’t support XQuery which is a major focus for eXist (plus, things seem a little quiet over at the Xindice project).

Orbeon Forms is a server-side XForms implementation. If you’re looking for an open source forms solution, you need to take a look. Orbeon is XForms, XProc, and eXist, all rolled into a single offering. You can merge the Orbeon WAR file with your web app’s WAR or you can deploy Orbeon in its own web app and simply tell it to handle all of the XForms tasks. Orbeon also has a graphical forms builder but I didn’t get a chance to play with that.

Thinking I might want to use Apache Sling/Jackrabbit as my repository, I decided to see how easy it would be to persist the XForms data into Jackrabbit instead of eXist, as Orbeon’s tutorial does by default. As I suspected, it turned out to be a 2 minute task. Because Sling provides a REST API into Jackrabbit, and because XForms can persist data via REST natively, it was simply a matter of changing the post URL from the eXist REST URL to the Sling REST URL and it was a done deal. Deciding whether or not Jackrabbit (instead of or in combination with eXist) is the right way to go is a decision for another day.

I’ll provide an update at some point down the road after we’ve done some implementation work on this embedded forms stuff and we’ll see how it actually held up.

Slinging some ideas around RESTful content

Via Seth Gottlieb news that Apache Sling has been officially released. Sling is interesting–I’ve played with it only a bit. You can read more about it on Seth’s post but essentially it is a REST API that sits on top of Apache Jackrabbit. Jackrabbit is the reference implementation of the JCR spec.

I’m not crazy about the JCR API because it is Java-only (yes, I know there are bridges out there). Plus, it doesn’t seem to be rich enough for many types of implementations. For example, Alfresco is a JCR-compliant (Level One) repository, but you don’t see too many people doing JCR-only interactions with Alfresco.

What is interesting to me, though, is the idea that you can abstract repositories at a higher level: the REST API. If we’re all going to talk to our repositories via REST, why not do it in a standard way?

Alfresco introduced a REST framework in 2.1 called “web scripts” (learn more). But Alfresco does not yet have a full-blown “REST API”. Yes, there are a few out-of-the-box REST calls but for the most part, when you interact with Alfresco via REST you are going to roll your own API. On Optaros projects, this has not yet been a huge burden. Quite the opposite, in fact–we’ve been able to develop everything from web script-backed JSR-168 portlets to a streamlined version of the Alfresco web client (soon to be released as an open source project), all on web scripts.

As part of 3.0, Alfresco anticipates rolling out additional out-of-the-box URLs to more fully establish the REST API. The new 3.0 web clients are based almost entirely on REST so they might as well build a REST API that we can all use.

When I look at Apache Sling, I’m thinking, why don’t we agree on a standard REST API for working with content repositories. Then, we could write a front-end once and theoretically use it with multiple back-end repositories. If someone then wants to use a JCR-compliant repository behind the scenes, then that’s cool, but it isn’t a requirement.

Obviously, there is a granularity challenge here. If the API is too granular the front-end ends up making too many calls. If you are aggregating multiple calls from within an intermediate application and then returning the result to the front-end (rather than making a bunch of AJAX calls initiated from the browser client), that’s not as much of an issue. If the API is too coarse, it is too hard to reuse across many different types of front-end applications.

Still, if we agree that REST is the preferred interaction model in the “content as a service” world, at least for the moment, and further, that front-end developers tend to want to have the option of using non-Java technologies for the presentation layer, a standard REST API for interacting with content repositories makes sense, whether that’s Sling, whatever Alfresco comes up with, or the best of both.

Maybe the Atom Publishing Protocol is close to what I’m thinking here. Maybe Alfresco thinks so too. I noticed the Abdera JAR was added to the Alfresco Community dependencies fairly recently. Abdera is an Apache incubator project for working with Atom.

We actually have an engagement with Alfresco right now to develop some of the new 3.0 web client modules. When I get some time I’ll explore this idea a little further by checking in on the 3.0 web client team, looking at Abdera, and doing a deeper dive on sling.