Lambda the Ultimate

Pardus Linux is a case study of functional Python. It's a Linux distribution built from semi-scratch, the main focii being package management and init subsystems - places where C and shell script make poor sense. A funded group has finally tackled these issues.

A package management software deals a lot with sets, lists, and dependency graphs....We have extensively used functional operators (map, filter, reduce) and list comprehensions, even metaclasses are used in a few places.

Someone nudge Guido. Scheme or Oz might have been the better choice, but give them credit. They admit frankly to social acceptance issues.

A Real-World Use of Lift

Well, lift is actually being used in production. I converted a Rails app to lift and it was a very interesting experience...

Then we did some benchmarking. For single request processing, the lift code, running inside Tomcat, ran 4 times faster than the Rails code running inside Mongrel. However, the CPU utilization was less than 5% in the lift version, where it was 100% of 1 CPU (on a dual core machine) for the Rails version. For multiple simultaneous requests being made from multiple machines, we're seeing better than 20x performance of the lift code versus the Rails code with 5 Mongrel instances. Once again, the lift code is not using very much CPU and the Rails code is pegging both CPUs.

In terms of new features, we've been able to add new features to the lift code with fewer defects than with the Rails code. Our Rails code had 70% code coverage. We discovered that anything shy of 95% code coverage with Rails means that type-os turn into runtime failures. We do not have any code coverage metrics for the lift code, but we have seen only 1 defect that's been checked in in the 2 weeks since we started using lift (vs. an average of 1 defect per checkin with the Rails code.)

So, yes, I'm pimping my own framework, and yes, I'm able to do with lift what guys like DHH are able to do with Rails, so the comparison is, in some ways, unfair.

On the other hand, Scala and lift code can be as brief and expressive as Ruby code. lift offers developers amazing productivity gains vs. traditional Java web frameworks, just as Rails does. On the other hand, lift code scales much better than Rails code. lift code is type-safe and the compiler becomes your friend (this does not mean you should not write tests, but it means that your tests can focus on the algorithm rather than making sure there are no type-os in variable and method names.)

I promise that "Dave Pollak" is not a pseudonym for "Paul Snively."

Update: I guess the self-deprecating humor hasn't worked, some 400+ reads later. Although the caveat that Dave offers about trying to objectively compare his own framework with Ruby on Rails is well-taken, I think that this nevertheless is an important marker in applying a very PLT-driven language and framework, Scala and lift, to a very realistic application, especially given that it's a rewrite from a currently-popular language and framework, Ruby and Rails. We admitted proponents of static typing and weird languages are constantly being asked for this sort of thing, and while it's doubtful that this adds anything to the PLT discussion per se—at least until we have a chance to dig into lift and see how Scala's design uniquely supports it—I thought people might find the Scala connection worth commenting on.

(Note: The title is meant to be humorous!)

XMLisp is the integration of Lisp with XML. The Lisp Meta Object Protocol is used to establish a simple and highly efficient mapping between CLOS objects and the XML extensible markup language. It is not just an API to read XML files and turn them into some Lisp flavored representation. Instead, it integrates Lisp and XML into one environment at two levels. At a language level it allows the arbitrary combination of Lisp expressions and XML elements. CLOS objects can be printed as XML elements. XML elements evaluate into CLOS objects. At a tool level XMLisp allows users to fluidly experiment with XML. Type XML elements into the lisp listener. Evaluate complete or parts of hierarchical XML elements. Inspect complex XML elements using the inspector. Get support from symbol completion when editing XML.

I stumbled across this while porting more layers of the Open Agent Engine to OpenMCL. While at first it seems a little weird, it's actually quite an amazingly natural way of integrating Lisp and XML.

It's neat to work with XML fragments as an inspectable CLOS object hierarchy. I think XMLisp is also a great example of the flexibility available to Lisps of all flavors; I'm sure some industrious soul could easily port it to PLT Scheme or something similar!

Ralf Lämmel and Erik Meijer. Revealing the X/O impedance mismatch.

When engaging in X/O mapping, i.e., when viewing XML data as objects or vice versa, one faces various conceptual and technical challenges -- they may be collectively referred to as the `X/O impedance mismatch'. There are these groups of challenges. (i) The XML data model and the object data model differ considerably. (ii) The native XML programming model differs from the normal OO programming model. (iii) The typical type systems for XML and objects differ considerably, too. (iv) Some of the differences between data models and between type systems are more like idiosyncrasies on the XML site that put additional burden on any X/O mapping effort. (v) In some cases, one could ask for slightly more, not necessarily XML-biased language expressiveness that would improve X/O mapping results or simplify efforts.

The present article systematically investigates the mismatch in depth. It identifies and categorizes the various challenges. Known mitigation techniques are documented and assessed; several original techniques are proposed. The article is somewhat biased in that it focuses on XML Schema as the XML type system of choice and on C# as the OO programming language of choice. In fact, XSD and C# are covered quite deeply. Hence, the present article qualifies as a language tutorial of `the other kind'.

This paper is over 100 pages, way longer than I have the time to read at the moment. Skimming, the paper looks interesting and useful. If you manage to read the whole thing, do share your observations with us in the discussion group.

(via Don Box)

This paper will attempt an objective side-by-side comparison of the two languages: not just from the point of view of technical features, but also looking at usability, vendor support, performance, portability, and other decision factors. Is it true, for example, that XQuery is better for data and XSLT is better for documents? Is one or the other language easier to learn depending on your computing background? As well as trying to answer these questions, the paper will also illustrate how the two languages can interoperate, so that each can be used for the parts of an application where it is most appropriate.

A comprehensive discussion by Michael Kay that, I think, wasn't mentioned here before.

A screencast about Microsoft's Atlas toolkit (Flash, Windows Media and QuickTime formats available).

Atlas it ASP.Net's AJAX solution, and it seems quite well thought out from what I can tell.

Both the ASP.Net Atlas code and the Atlas XML Script DSL provide a declarative programming model, which should help build AJAX applications which otherwise require a somewhat confusing programming model for beginners.

It sohuld be interesting to see how this approach compares with web frameworks such as Rails (whose DWIM approach makes it quite DSL-ish), and with the approach Wadler takes with Links.

Following the story on Mind Mappers and other RDF comments of late, I thought this NLP slide show (PDF) should get a story. Dr. Adrian Walker offers an interesting perspective in a friendly crayon-colored format, including a critique of RDF. Source site Internet Business Logic has other offerings including an online demo.

The X in XML stands for “Extensible”; one big selling point is that you can invent your own XML languages to help you solve your own problems. But I’ve become convinced, over the last couple of years, that you shouldn’t. Unless you really have to. This piece explains why. And, there’s a companion piece entitled On XML Language Design, in case you do really have to.

Ouch.

OS and web search vendors are merging desktop search into their offerings. Vendor solutions vaguely worry me. They seem too focused on the home PC and not on business needs, while needlessly bypassing RDF. There's also vendor lock, bad EULAs, privacy negligence, and lost boundaries between OS, applications, and data - proprietary black boxes tempting us into dependence.

That thinking led me to the open-source Mind Raider program. It's one of the few that makes RDF useful for normal people. It compares to Chandler but focuses less on email and calendars. As far as I know, Chandler doesn't expose RDF or even use it, necessarily. However the Mind Raider Big Picture shows similarity to Chandler's vision.

So why should this stuff matter to LtU. Well, compare formal organization between data that only computers inspect and data that people use daily. Many database systems exist to store data in the former category. Employee and customer address data serves little purpose beyond printing paychecks and shipping labels. A human will not care about values except that they not be empty. Granted that people do use databases to track sales figures and other aggregates. Still even those folks use data in the latter category: stray thoughts and reminders, sticky notes, social and business correlations, restaurant napkin sketches, collaborative data, recorded conversations, news clippings. A large cloud of miscellany doesn't rise to the level of application documents or the formality of enterprise systems.

Few systems exist to aggregate and organize that stuff. If your brain suffices, then good for you. The rest of us need a crutch. Some people use spreadsheets to store lists simply because there's little else available. I've used software which imitates sticky notes on screen. It leaves much to be desired. There are dozens of little programs for narrow data types - address books, internet bookmark apps, password managers, photo albums, etc. How do you tell the address book that the photo album has pictures of the guy, and that his web link lives in the bookmark manager? Right now, you don't. And programs never organize data just the way you want. Besides, exceptions to the common format always arise. So the problem is not just searching documents and email, nice as that is, but organizing human details in useful ways. Moleskin notebooks and Dictaphones have been around a long while. It's time for cool software.

Somehow RDF seems primed for the role, but it needs less abstract public relations. Raw RDF may not be the ideal presentation but still seems a likely candidate for the underlying data model. Each individual develops a personal ontology (aka "working style" if you will) over years of time. RDF can capture that, but it will take friendly programs like Mind Raider. What do you think?

The apps are built using PHP and a simple XML-vocabulary based DSL called XNHTML.

As I've been saying for a long time here and elsewhere, it's all about programmability these days, and as the Ning folks realise DSLs are a very good technique for achieving end-user programmability.

Seems to me they could have gone the extra mile, and eliminated the need for PHP altogether, but I guess that would be asking for too much...