Posted by mchampion
on December 19, 2003 at 6:58 AM PST
Some thoughts, and links to other discussions, inspired by a speech given by Adam Bosworth last week. Topics touched on include the KISS principle and its breakdown in the XML world, hopes that Father Darwin wil set things right, the challenges of effectively using low-powered mobile devices in an internet optimized for fat pipes, and spins off into a discussion of the ideas behind JXTASpaces as an alternative to the competing distributed object and REST approaches to this kind of application.
[Another look back at the XML 2003 conference
last week. I feel sortof blogspherically incorrect in waiting a week to write
down these thoughts, but I wanted to let them bounce around a bit, and look at
what others wrote.]
Adam Bosworth of
BEA delivered the opening keynote address on Wednesday. He started by reminding
us of the dream that XML geeks shared back in 1998: Information should not get
lost in presentation. Actual XML practice has to some extent diverged into two
separate streams -- documents on one hand, and application data on the other --
but together they have helped take back the world from the "hideous complexity
and fragility" of information presented in .DOC, .EXE, etc.
I started to summarize the talk
itself, then came upon Matt May's excellent
I'll just elaborate on a few points that resonated with
Bosworth notes that one of the
negative aspects of the current XML world is that the KISS (Keep It Simple,
Stupid) principle is being widely ignored, as XML and Web services technologies
are becoming extremely complex. Bosworth has pointedly noted the complexity of
W3C XML Schema and XQuery in the past; this time he said something like
"there's only one guy in our company who *really* understands WSDL" ... and "we
don't need all these layers of coordination/orchestration specs on top of SOAP,
we need something like a 'SOAP cookie'." It's heartening to see more and more
people pick up on the theme that the XML family of specifications is too
complex, since I've been beating this drum for a long time now.
It's definitely time for some serious
refactoring of the the family of XML specs, and that won't happen until more
people of Bosworth's stature start telling the unpleasant truths about what a few
thousand person years of Design By Committee will do to a technology that used to be simple. The video clip from
Bosworth's presentation in Jon Udell's weblog has my favorite quote from the
talk: After admitting that 50 people would come up with 75 different ways of building distributed systems ."Some will win, some will lose. That's just fine. It's called evolution. It works really well. It's why we're all sitting here today." Maybe a bit of Darwinian Refactoring is what is called for on this stuff.
major theme in the keynote was that XML developers are asked to use "APIs from Hell."
For example, a programmer working with a purchase order in XML format must deal
with events, or child/sibling nodes in a tree, rather than application-level
concepts such as products and quantities. Hmm, that's a posting in and of
itself, because it ties in with a town hall meeting on storing/querying XML that
turned into a discussion of XML APIs. More later.
Probably the most unconventional
topic Bosworth spent time on was the importance of getting XML data models and
APIs suitable for handling the synchronization of intermittently connected
devices to Web-based master databases or applications. He noted that he spends
much of his business week using only his Blackberry device. Effective use of
such web-enabled, but slow and UI-challenged devices will require better
synchronization tools: queries are difficult to generate with a handheld UI, and
their limited bandwidth (if connected at all) means that it is important for
queries to be very optimized to return back only the information the user really
wants. Since this is so far beyond the state of the art, it may be easier for
the device to anticipate the types of data the user will want, and trickle than
information into the device in advance, as bandwidth is available, rather than
Bosworth presented a slide
outlining a "Mobilized Data Model" that might help guide work on this. I
suspect that many other listeners were also intrigued, but a bit mystified by
this-- a planned demo wasn't ready in time for the conference. It has, however,
generated some interesting discussion on the Web, not so much on the still-fuzzy
details of the data model, but on the deeper issues. For example, Tim Bray
that he is skeptical of the basic assumption behind the widespread need for
synchronization, since "the trend is clear:
anyone who wants to will be able to have a
pipe that's always
on." I'm not sure which side I come down on, but there is definitely two world
views here: Those who assume that there will be a significant amount of data on
the handheld device that must be synchronized with a central repository, and
those who assume that in general the remote device will be able to query the
central repository for the data it needs for a given task. Bosworth did offer
one data point that might argue against Bray's position: At best, in the
best-served places in the world a GPRS (General Packet Radio Service -- used for
"always on" connection to the Internet by mobile devices) request takes 1 second
to fulfill, and more if any significant amount of data is transmitted. Unless
we get a WiFi network that is as extensive as the GPRS network today, it's not
clear that the "fat pipe" assumption is realistic.
Another point that Bosworth has
explored, not so much in his speech but in his weblog. How can one address the difficult challenge of synchronization without falling into the trap of complexity that will not scale to the Internet, or even work on a limited power and bandwidth device? He's asking a lot of questions about REST in the weblog, getting lots of answers, but one gets the impression that they are not satisfactory.
Inspired by a posting by Vanessa Williams , I'll put in a plug for the ideas behind JXTASpaces (sortof tuplespaces/Javaspaces using XML rather than objects) as a way of bridging the gap between the web services ideas that Bosworth talked about and the REST stuff that intrigues him. (Williams doesn't make the link to Bosworth in the posting, but has done so privately) . Kimbro Staken picks up the thread and mentions how an XML DBMS that supports XPath can make the template lookup feature of tuplespaces easy to implement if XML documents are the "tuples." I think they are definitely on to something here -- See Robin Cover's summary of some technologies and discussions, including some comments by me. The one point that's most relevant to synchronizing mobile devices is that coordination via "spaces" allows loose coupling in time as well as space -- not only can components in a distributed system employ different platforms, languages, and native data formats, they don't even have to be running at the same time. On the other hand, product ideas such as Ruple went nowhere and even the open source JXTASpaces project is a not exactly thriving. Is this just an idea whose day has not yet come, perhaps like hypertext before HTML? Or is there not really a "there" there? I'm pretty sure that if any application domain is tailor made for an XML Spaces approach, it's intermittently connected mobile devices!
Finally (just when I thought I was finally done blogging this speech!), Joe Chiusano asks about the apparent contradiction between Bosworth's focus on simplicity and BEA's co-authorship of a somewhat daunting list of Web services specifications. It will be interesting to see if Joe gets an authoritative answer from BEA; my guess is that they are telling it like it is in a recent press release that suggests [at least in my reading between the lines!] that customers are giving them the message that the current way of doing things is too complex.