XML
An Introduction and a JavaScript RDF/XML Parser
My name is David Sheets. I will be a sophomore at MIT this fall. I like to be at the intersection of theory and practice.
This summer, I am working as a student developer on the Tabulator Project in the Decentralized Information Group at MIT's CSAIL. My charge has been to develop a new RDF/XML parser in JavaScript with a view to a JavaScript RDF library. I am pleased to report that I have finished the first version of the new RDF/XML parser.
Before this release, the only available RDF/XML parser in JavaScript was Jim Ley's parser.js. This parser served the community well for quite a while but fell short of the needs of the Tabulator Project. Most notably, it didn't parse all valid RDF/XML resources.
To rectify this, work on a new parser was begun. The result that is being released today is a JavaScript class that weighs in at under 400 source lines of code and 2.8K gzip compressed (12K uncompressed). For maximum utility, a parser should be small, standards-compliant, widely portable, and fast.
To the best of my knowledge, RDFParser is fully compliant with the RDF/XML specification. The parser passes all of the positive parser test cases from the W3. This was tested using jsUnit -- a unit testing framework similar to jUnit but for JavaScript. To run the automated tests against RDFParser, you can follow the steps here. This means the parser supports features such as xml:base, xml:lang, RDF Collections, XML literals, and so forth. If it's in the specification, it should be supported. An important point to note is that this parser, due to speed concerns, is non-validating. Additionally, RDFParser has been speed optimized resulting in code that is slightly less readable.
The new parser is not as portable as the old parser at this time. It has only been tested in Firefox 1.5 but should work in any browser that supports the DOM Level 2 specification.
RDFParser runs at a speed similar to Jim Ley's parser. One can easily construct example RDF/XML files that run faster on one parser or another. I took five files that the tabulator might come across in day-to-day use and I ran head-to-head benchmarks between the two parsers.
Parse time is highly influenced by compact serialization. The more nested the RDF/XML serialization, the more scope frames must be created to track features from the specification. The less nested, the fewer steps to traverse the DOM, the more triples per DOM element.
Planned in the next release of RDFParser is a callback/continuation system so that the parser can yield in the middle of a parse run and allow other important page features to run.
API documentation for RDFParser included in the Tabulator 0.7 release is available.
Finally, I'd be happy to hear from you if you have questions, comments, or ideas regarding the RDFParser or related technologies.
On GData, SPARQL update, and RDF Diff/Sync
The Google Data APIs Protocol is pretty interesting. It seems to be based on the Atom publishing protocol, which is a pretty straightforward application of HTTP and XML, so that's a good thing.
The query features seem to be less expressive than the SPARQL protocol, but GData has an update feature, while the SPARQL update issue is postponed. Updating at the triple level is tricky. I helped TimBL refine Delta: an ontology for the distribution of differences between RDF graphs a bit, and there's working code in cwm. But I haven't really managed to use it in practical settings. My PDA's calendar has an XMLRPC service where I can update a whole record at a time, just like GData. I assume caldav does likewise.
The GData approach to concurrency looks quite reasonable. I haven't studied the authentication mechanism. I hope to get to that presently.
RDF Calendar, GRDDL, Microformats, and all that at XML2005 in Atlanta
My talk was:
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@ 2:45 on Weds
:
Semantic Web Calendaring: RDF Calendar, hCalendar,
and GRDDL
I spent a lot of time preparing my slides, Semantic Web Data Integration with hCalendar and GRDDL, but at show-time, there were still too many. I had to basically skip over the cool OWL DL consistency checking example that I spent the better part of two days putting together, but I'm OK with that; the more basic points were more important.
I unfortunately didn't leave any time for questions, but I had some interesting follow-up conversations:
- Somebody asked about using GRDDL and RDF to track relationships between specs, products that support them, and all that. I recalled that when the folks that run the OASIS standards registry contacted W3C, we told them we prefer a more decentralized approach: each organization publishes stuff about their own standards, in RDF, and anybody can aggregate it. TimBL's roadmap diagrams show one approach. It is somewhat bit-rotten, but we have an automated system in production for publishing basic title/author/date/version metadata about our specs and we're adding more stuff over time; e.g. which WG produced the spec (for patent policy reasons), comment due dates, etc. I told him this had come up in spec-prod; while I'm happy for the discussion to go there, my impression that it had come up there before was wrong. I hope to organize my thoughts on this near NormativeReferences in the QA/ESW wiki and re-kindle discussion in spec-prod or qa-ig.
- At lunch, somebody brought up my slide about email headers in RDF and asked if thunderbird has RDF support like mozilla and firefox. I don't know, but I hope to find out. DanBri? Anyone?
On the non-technical front, jamming with Len Bullard was a blast. We had a fascinating discussion of DRM and the recording industry where I relayed AaronSw's viewpoint that any model based on scarcity is uninteresting. Len says Prince is no longer independent, which contradicts the impression I got from studying Prince in Wikipedia recently. Len says the big customer ripie for SemWeb technology is transit, at least as much as intelligence. Gotta look into that.
Later in the evening Len brought out a fake book and Tony and Lauren and Eve and John sang and I tried to accompany them on Len's guitar. I was having so much fun that I raised a sizeable blood-blister on my strumming hand before I noticed. I think we did OK with Annie's Song as well as mangling lots of Beatles and such.
Then Len took the guitar and Eve asked him to play Angel from Montgomery by Bonnie Raitt. When he said he didn't know it, I was able to use my sidekick to find chords and lyrics and since it was your basic three chord number, he picked it up in no time.
As to the conference program...
Tue 15 Nov
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@09:00.Opening
Keynote: From Atoms to OWLs the new ecology of the Semantic
Web
Jonathan Robie said Jim made 5 or 6 points in this talk that had been obscure, at best, in earlier talks on the Semantic Web in RDF. Kurt Cagle's notes don't seem to show them.
Unfortunately, the DAWG teleconference started at 9:30 and missing it would have delayed the WG by several weeks, so I ducked out.
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@11:45.Handling
Math in Real-World Workflows: Practical Lessons
What jumped out at me was that primary school publishers are hot on MathML content markup for reasons of accessibility. It's good to hear that the theory that higher levels of semantic abstraction contribute to accessability plays out in practice.
I asked if XSL-FO was on the map in this world of production math workflows, but he said no, not really.
I wanted to ask
what would you change about mathml if you had a time machine?
but didn't find the right moment. -
@14:00.Modeling Methods and Artifacts for Crossing the
Data/Document Divide
He had this great slide (5 of 37) showing that business data goes from narrative documents (catalogs) to transaction data (orders) and back to narrative (support docs) and that data models need to cross them.
An HL7 person asked
how important is it to trace back from document to data model?
which prompted me to add a slide to my talk to make the point about how GRDDL lets you get from narrative documents back to UML-like models. -
*14:00.Federated Identity Management: An Overview of
Concepts and Standards
I really wanted to get this overview from Eve, but I got caught in a hallway conversation or something and missed it. I picked up some of how Liberty works from the next talk. ID-FF looks an awful lot like OpenID. I wonder what's the difference.
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@14:45.Liberty Federation Deployment Case Study
This showed real-world deployment of federated identity services remarkably like the ones we discuss in the PAW project. I asked a lot of questions about the details, and the answers were quite reasonable. Afterward, I said to Eve and Yvonne,
Would you slow down? We're trying to pitch many of these ideas to research funders. If you deploy them all in commercial settings, where will we be? ;-)
At some point, she mentioned government rules where authorization data was considered sensitive but authentication data was not. I hope to get more details about that.
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*14:45.Microsoft's Language Integrated Query and XML
I heard this was a great talk; both the content and the presentation. I hope to get notes from Norm, Michael, and others who were there.
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@16:00.The Atom Publishing Protocol: Publishing Web
Content with XML and HTTP
Most of the stuff he presented looked familiar; looks like not much has changed since the last time I saw Joe give a talk on the Atom protocol. He mentioned
great article by Udell on URIs
... ah... Tangled in the threads seems to be a column that Udell used to write for Byte. Anybody got a pointer to the article Joe was talking about? I'd like to cite it among the TAG educational materials. -
@16:45.Remixing RSS - past, present and future
An interesting perspective of the development of blogging. At their booth, I discovered bryght is a big drupal shop. I asked them about in-browser direct-manipulation editing; they're big on TinyMCE.
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*16:00
.Names, Namespaces, XML Languages and XML Definition
Languages
I think Henry alluded to this paper in a TAG discussion of XMLVersioning-41 in Edinburgh. I was looking forward to getting it presented conference-style, but I guess I can read the paper and discuss it in the TAG.
Wed 16 Nov
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*
11:45 . On Language Creation
missed this in the panic of preparing for my talk. Darn.
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*
11:45 . Native XML Scripting with ECMAScript for XML
(E4X)
missed this in the panic of preparing for my talk. Darn.
- @ 14:00 . XSL Transform Self-Documentation
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*
16:00 . XML, REST, and SOAP at Yahoo
Wanted to follow up on the conversation we started briefly in his blog but it was scheduled against a SPARQL session. Had to settle for a brief hand-shake and card exchange.
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@
16:00 . SQL, XQuery, and SPARQL: What's wrong with this
picture?
What looked like a SPARQL-bashing session turned into a pretty good SPARQL tutorial. Jim Melton, who has been doing SQL standards work for over 20 years and sharing that experience in the XQuery WG for several years, took a close look at SPARQL, prompted by some nifty results by some folks using RDF/OWL in drug discovery. Even though he was "strongly encouraged" to conclude that SPARQL was obviated by SQL and XQuery, his conclusion was that it has a place.
Thu 17 Nov
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*
09:00 . Describing Web Applications
missed the talk but spent some time noodling on WebDescriptionProposals in the ESW wiki. I hope to study WADL more closely.
- * 09:00 . Semantics and Security: Applying RDF and OWL to Defense and Security Challenges
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*
11:00 . The Impact of XML on Contract Law and the Volume of
Contract Litigation
I didn't get to see Jane Winn's talk (though it won an award and I look forward to reading the paper), but after Bob G. introduce me to her in the exhibit hall, we had a fascinating discussion of the social side of open source and open standards. There's some seminal paper on charismaric leadership that she's supposed to be sending me. I asked for a pointer, but it seems to come from the pre-Web world of paper and fax machines.
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@
11:00 . Unit Testing in XSLT 2.0
Some comments on XSLT 1.0 were pushed back a la
but wer're just doing a transformation language for stylesheets, not a general-purpose programming language.
Maybe so, but clearly XSLT 2.0 is sufficiently general purpose to build unit testing harnesses. -
@
11:45 . Automated mass production of XSLT stylesheets
Using a spreadsheet as a way to communicate design requirements and even decisions from users to developers and/or straight to the machine. Cute. Reminds me of my own work on using spreadsheets as an RDF authoring tool.
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*
14:00 . "Just" Use XML
His slides have great stuff on pitfalls of XML, unicode, dateTime, etc.; filed it under quality
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@
14:45 . A Generalized Grammar for Three-way XML
Synchronization
This was much less relevant to our work on RDF diff/sync than I thought it might be, but trick of using SVG animation to show differences between images was really cool.
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@
16:00 . Using XSL, XForms and UBL together to create
complex forms with visual fidelity
I have missed so many chances to soak up XForms at a conference... I finally made the time for this one, but it turned out to me more about XSL-FO.
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@
16:45 . Enterprise-level Web Form Applications with XForms
and XFDL
John Boyer is an
XForms WG co-chair, as well as doing DSig stuff. He's now
at IBM, since they acquired Pure Edge. Hendler got the
two of us together in the hall to discuss some connection
between XForms and SPARQL... something about using XForms
in the role that XSLT plays in handling SPARQL results.
Hmm.John asked that we "don't think of a Form as just the typical name/address or pizza order form"; likewise, he asked us to put aside our notion of table. But I didn't get a firm feel for what we're supposed to put in thier places, except that a form can be a blackjack game.
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@
20:00 . Closing Keynote: Everyone's using XML,
but does anyone care?
Very entertaining. On Web services, he said
we've got this little pea of xml under all these layers and only a true xml princess can feel it.
