Extreme Markup Languages 2004


8 August 2004

The Extreme Markup Languages conference proudly differentiates itself from others XML conferences by (amongst other things) its willingness to foster dissent from XML orthodoxies, its low tolerance of marketing speak and generally by having higher-than-average geek-appeal. This year's event, held at a curiously decorated downtown hotel in Montréal, certainly lived up to the stated goals. The following biassed, ill-informed, and unreliable report should be read in conjunction with the complete online proceedings and indeed the official photo page.

Tommie Usdin (Mulberry), chair of the conference, opened proceedings with what sounded like a tried and tested rehearsal of the conference objectives and guidelines. This year, for the first time, nearly all of the submitted proceedings had not only used the right DTD but validated against it. Some however had been hoist with the petard of over ingenuity — in Tommie's memorable phrase ‘Mathml may be ready for prime time but it's not ready for amateur use’.

James Mason (no, not the movie star, the SGML star), reported some experiments he'd been trying at something called the Y12 Manufacturing Facility of the US National Security Agency. This is a very long established military factory complex whose products range from the enriched uranium produced originally for the Manhattan Project, to special widgets for banjos (mercifully, he didn't tell us what the military does with its banjos) and complete off-the-shelf field hospitals. The complexity of its operations and consequently its data resources, seemed to Jim to make it a good candidate for explication via a topic map, and why not. His protoype web application demonstrated how the topic map worked as an effective way of navigating complex interdependencies amongst all bicycle-related resources. In answer to that FAQ, ‘what's special about topic maps?’, Jim opined that it was the ability to index and merge different kinds of data. This was fun but not, forgive me, rocket science.

Second plenary of the conference was a double-act involving two people from a health industry consultancy Pensare called Duane and Renee. Their big idea was that because the terminology used in any specialist field changes over time, development of ontologies and topic maps derived from them needed to build in a significant usage monitoring component. (At least, I think that's what it was). Duane and Renee advocated something alarmingly called `stealth knowledge management' techniques to help address this problem, which on interrogation seemed to mean paying attention to the informal ontologies people actually start using after the expensive formal ontology-creating consultants have left — presumably by retaining said consultants on a permanent basis. It's hard to disagree with Renee's pitch ‘usability isn't an end point, it's an ongoing process’; harder to see what you do about it.

Over lunch, I chatted informally with Terrence Brady from LexisNexis and learned that they use a topic map to navigate the horrors of the system documentation associated with their thousands of different databases, which was reassuring. After lunch, we split into parallel sessions, one (in the Incognita room) being mostly devoted to über-geeky reports on cool hacks, and the other (in the Mont Blanc room) less so. In the former category, I tried not very successfully to follow Bryan Thompson explain how existing HTTP GET (etc) commands can be used to access XML fragments from large scale web resources using Xpointer and something I've never heard of called the REST (`Representational State Transfer') architecture. This was followed by the first of several reports from current German computer science departments: Sebastian Schaffert (Munich) on a new declarative query language called Xcerpt, the key feature of which is an explicit separation of the process of querying resources and constructing their results. The claim is that Xpath in particular confuses these two in a very unteutonic way, and that separating them again better facilitates rule-chaining and other reasoning processes needed for the semantic web; he's probably right, but I don't think I can explain why.

After tea I returned to the Mont Blanc room to listen to Steve Pepper (Ontopia) announce how topic maps had taken over if not the world then at least the whole of Norway. Work on a Government-funded e-learning project has put Ontopia into the enviable position of being able to define a `Semantic Portal', that is, a group of subject-specific portals each of which exposes its contents by means of a topic map, and which can therefore be accessed as a group, using a single `identity mechanism' to identify when topics can be mapped to one another. Allegedly, the philosophers' stone in question is achieved by the use of Published Subjects, (Steve referred to this as the semantic superhighway), and TMRAP, which is a protocol for remote access to both topic maps and — critically — other resources as if they were topic maps; the final piece is a topic map-specific query language now being discussed within ISO. In an access of enthusiasm, Steve said that these constituted the building blocks of ‘seamless knowledge’ and would allow us to achieve all the semantic web promised and more. I don't think I was alone in feeling a little sceptical about this.

Last paper of the day, back in the Incognita suite, was Eric Miller (formerly at OCLC now at W3C) whose title, abstract, and presentational style all promised rather more than was actually delivered. The subject was mapping between one specific XML schema and an RDF representation using XSLT; the use case was Michael Sperberg-McQueen's sui-generis calendar data and Eric's own; a harsh critic might say that since the main purpose of the application discussed was to find a way of scheduling time for the two authors to plan the content of their paper, the lack of content in the paper demonstrated rather well the viability of this approach. However, Eric did do a very good job of re-problematising the issues of semantic mapping which Steve's presentation had somewhat obfuscated with marketing hype.

Day two of the conference was largely devoted to papers about Overlap, a major theme of the conference and also the pretext for some amusing lapel pins being handed out by Patrick Durusau. Andreas Witt (Bielefeld) gave a rather good summary of the current state of knowledge about how to handle concurrent structures, endearing himself to me greatly by demonstrating how little the state of human knowledge on this has advanced since the TEI originally discussed it in the late eighties. The issue seems to be not so much how to choose between the different possible ways of representing overlapping structures in markup (TEI milestones, standoff, MECS, LMNL...) as how on earth to process them effectively. Andreas suggested conversion to a set of prolog facts (using python) and gave a good overview of the sorts of meta-relations recoverable from such a re-encoding of multiple layers of annotation.

Patrick Durusau, wearing a remarkably silly Gandalf hat, covered basically similar ground, but used a simple relational database rather than a prolog fact base as engine. He also reported availability of a sample data set — the first few books of Milton's Paradise Lost marked up with page/line hierarchies from different editions, and also with sentence and clause analyses (but not, regrettably for Miltonists, speaker divisions), which sounds like a good test for such systems.

In the absence of Steve De Rose, Tommie Usdin briefly summarized his very thorough presentation of — guess what — the various ways available of presenting overlapping hierarchies. Steve's paper featured a number of varyingly memorable metaphors, most notably the concept of `Trojan milestones', involving start- and end- pointers on empty versions of otherwise ordinary looking structural elements. He proposed a formalism called CLIC (for ‘canonical LMNL in XML’).

Wendell Piez reminded us that overlapping and multiple concurrent hierarchic structures were not exactly the same problem. He gave an update on the purpose and nature of LMNL (Layered Markup and Annotation Language) which he and Jenni Tennison had presented in 2002. Since then, Alex Czmiel had produced an implementation of this non-XML based data model, but, as Wendell agreed, the problem of how to process it remained. He also reported availability of a nice dataset (heavily annotated extracts from Lord of the Rings) and demonstrated how it might be processed by conversion to what is effectively milestone-only (or COCOA-style) markup; several people suggested that LMNL could usefully be simplified by not treating annotations on annotations differently from any other kind of annotation.

After lunch, I fear I paid less attention than I should have to two more German computer scientists: Christian Siefkes (Berlin) presented an algorithm for automagically tidying up well-formedness markup errors which didn't appear to convince anyone. Felix Sasaki, from Bielefield, discussed rather more fundamental issues about ways of representing markup semantics independent of their instantiation, and thus mapping between different schemas (I think), the erudition of which appeared to stun everyone into silence.

After tea, there was a rather comical panel featuring several of the available topic-map heads (Patrick Durusau, Lars Marius Garshol, Steve Newcombe, Ann Wrightson). It seems that the ISO work group charged with defining a topic map reference model as a complement to ISO 13250 (which defines the terminology and ISO syntax for topic maps) had met immediately prior to the Markup Conference, and discovered they all disagreed about what that reference model might be. Garshol had the enviable task of reporting this contretemps, which he did in a rather disarming way; the other panellists then proceeded vigorously to disagree with each other to everyone's satisfaction and we all went to dinner.

Day three of the conference opened with Liam Quinn, also wearing a very silly hat, who now works for W3C, and thus has time to worry about old chestnuts like the feasibility of standardizing a binary format for XML. A W3C activity chaired by Robert Berjon has been formed, which will collect usecases and report after 12 months whether or not there is a case for doing the technical work needed to define such a thing. As Lee pointed out, it's in the XML dogma that all processors would be able to understand all XML documents, which seems to suggest that proposing a standard for ‘islands of binary goop’ (his phrase) would not stop them remaining insular. On the other hand it's clear that plenty of user communities do need binary formats (Lee talked about delivering PDF fragments and extracts from multi-gigabyte map data to memory-challenged handheld devices) so reducing the number of such competing formats might be advantageous.

Matthew Fuchs' plenary, which followed this, was a rather more technical piece about ways of adding object-oriented like features to XML processing, in particular the use of the element() function in XSLT2 which seemed to offer the only way of taking advantage of the inheritance and compositional properties definable for elements in W3C schema. The XSD-based UBL (Universal Business Language) (which Matthew claimed was on the verge of world domination) uses these as a framework for extensible schemas, but the tools are lacking. He reported in more detail than I could follow his success in adapting Ken Holman's stylesheets for UBL to use polymorphic classes. Norm remarked that XSLT2 (still a moving target) now does more of what was needed for this purpose.

After the coffee break, I paid only cursory attention to a presentation about DITA, which seems to be a kind of topic map application for integration of technical documentation systems, and was mildly nonplussed by a presentation shared by David Birnbaum and David Dubin. The former explained at some length the principles of Russian versification, while the latter gave us a demo of a prolog program which inferred the presence of textual features such as rhyme from markup of phonological features. Allen Renear explained to me over lunch that the point of all this was to demonstrate that the information recoverable from a marked up text was not necessarily exhausted by the markup itself. I found this insight distinctly underwhelming, no doubt because I was worrying about my own presentation.

I presented the current state of the ODD system developed for production of TEI P5, emphasizing its features for modularity, modification, and internationalisation, and was politely received, but (rightly) taken for task for overstating our desire to ditch DTD users. Syd and Julia continued the ODD theme with a discussion of some of the implications of extensive user modification, also outlining some limitations of what could currently be customised in P5, notably the documentation. (We need to find a way of translating the TEI GIs that are referenced in the text). The day finished with a very nice presentation from Norm Walsh about the way in which DocBook is going down the same righteous path as TEI in its RelaxNG-based modularization.

Simon St Laurent kicked off the last morning of the conference by tackling another of those things we thought XML had disposed of: namely general entities. He reminded us of all the nice things you can do with them and how xinclude really doesn't hack it. The DTD declaration may be dead in an XML world, but it isn't lying down as long as we need to use general entities. Simon's suggestion is to use a pre-processor to do entity management; he reported progress on (and some details about the inwards of) his ents parser (http://simonstl.com/projects/ents/. Since however the XML committee has reportedly opined that ‘existing methods suffice’ there doesn't seem to be much future in this.

Another grand old man of the SGML world, Sam Wilmot, original developer of the Omnimark language, gave an entertaining and discursive talk about pattern matching languages like icon and snobol; in particular he presented an implementation of pattern matching primitives in python. His main point was to remind us that pattern matching was a useful technique not adequately supported by most currently available XML processors.

Nicest surprise of the conference was Eric van der Vlist's talk. He reported a successful project which has provided for DocBook more or less the same customizing functionality as we hope to provide for TEI with the new ODD system, using nothing up his sleeves and no software fancier than an Open Office spreadsheet and some XSLT scripts.

Extreme appears to have a tradition of allowing Michael Sperberg McQueen to deliver a closing sermon: this year's text was the word model as in ‘XML has no formal model’, an accusation which Michael triumphantly rebutted, with his customary wit, erudition, and length, not to mention appeals to formal logic theory and corpus evidence. I did feel a little worried that he felt it necessary to ask us whether the solar system modelled the theory that the earth goes round the sun though.