Getting it in writing: [Closing remarks at Extreme Markup Languages® 2005]

C. M. Sperberg-McQueen


Closing Keynote: The letter killeth, but the spirit giveth life. Or was it the other way round?

Keywords: Markup Languages

C. M. Sperberg-McQueen

C.M. Sperberg-McQueen is a member of the technical staff at the World Wide Web Consortium; he serves on the W3C XML Schema Working Group and chairs the XML Coordination Group.

Getting it in writing

[Closing remarks at Extreme Markup Languages® 2005]

C. M. Sperberg-McQueen [World Wide Web Consortium, MIT Computer Science and Artificial Intelligence Laboratory]

Extreme Markup Languages 2005® (Montréal, Québec)

Copyright © 2005 C. M. Sperberg-McQueen. Reproduced with permission.

Thanks to Kate Hamilton of Mulberry Technologies for transcribing this from tape. She and I have taken the opportunity to repair a few sentences and improve a few transitions, but mostly the text below is what was said rather than what one might wish I had said. I've left Kate's indication of audience reaction and added some footnotes where I thought people might be interested in additional information.

Hitting the balance

There is a strain in our culture which distrusts writing things down.

There is another that says writing things down is essential.

“Getting it in writing” is a pejorative, sometimes jocular, way of expressing distrust. Surely the only person who wants to get an agreement in writing is one who distrusts the other; much better to say of someone that “Their word is their bond.”

On the other hand, people who want too much freedom of action make us nervous unless we trust them implicitly. Unless we trust them implicitly, we don't know exactly what they're going to do.

Those of you who, like me, grew up listening to Charlie Mingus records may remember from the liner notes on Mingus Ah Um the story about a jazz workshop where Mingus brings in a composition where he's left a few measures open for improvisation. The musicians say, “You're getting lazy, man! Write it down, write it out!”1

That's the tension that I see.

I have been thinking lately that we as a community may not be hitting exactly the right balance with regard to that tension.

Rules written and unwritten

There have been tensions over the years, sometimes minor, sometimes more major, in the W3C as in other standards-development organizations, in part because the W3C started with the goal of having a really light-weight process: there was a widespread perception that written procedures slowed things down. Well, that's true. They do.

There was a desire to get some written rules that working groups could trust and work by; and there was a certain resistance by some of the W3C staff, including Tim Berners-Lee, which made some people suspicious; it made me suspicious, before I started working at the W3C and got to know Tim Berners-Lee better.

Part of the issue was transatlantic. I have to remind myself even now that Tim grew up in a country governed by an unwritten constitution, and they're proud of the fact that it is not written down. It gives you flexibility when the chips are down, in ways that the American constitution doesn't always. (Unless, of course, you ... No, let's not go into Supreme Court issues!)

More generally, I think we've all had ample opportunities to observe a general distrust on the part of many geeks of written procedures, parliamentary procedures.

In part this is part of an endemic distrust of democracy on the part of technically-oriented people. It's hard not to mistrust majority rule if you grow up going through school being one of the brightest in your class and knowing that if two of you say the answer to this math problem is x, and 27 other people in the room say the answer is y, the chances are that you're right, not them. It's hard to learn to trust majority rule after enough experiences of that kind.

But I think mistrust of democracy is only part of it.

Information vs wisdom

Part of it is mistrust of writing things down, of losing the flexibility that you get when things are not written down.

This goes way back in our culture. The subtitle of my talk is from 2 Cor. 3:6 - “For the letter killeth but the spirit giveth life.” That has been interpreted in a lot of different ways. The spin I'm going to put on it is that if you follow the strict letter of the law, you're not necessarily following the spirit of the law. The spirit, in this Pauline view, is more important. Some of the time I think that's right; some of the time, I'm not so sure.

The distrust of writing goes back farther than Paul; Paul got it from Greek philosophy; Greek philosophy got it from Socrates and Plato. There is a well-known passage in Plato's Phaedrus, which some of you will have been expecting me to quote; I hate to disappoint anybody, so I'll quote it:

The god Theuth (or Thoth) has invented writing and he takes it to the king Thamus. Theuth says that writing will make people wiser, and improve their memories. Thamus replies:2

O most ingenious Theuth, the ... inventor of an art is not always the best judge of the utility ... of his own inventions .... And in this instance, you ... have been led to attribute to them a quality which they cannot have; for this discovery of yours will create forgetfulness in the learners' souls, because they will no longer use their memories; they will trust to the external written characters and not remember of themselves. The specific which you have discovered is an aid not to memory, but to reminiscence, and you give your disciples not truth, but only the semblance of truth; they will be hearers of many things and will have learned nothing; they will appear to be omniscient and will generally know nothing; they will be tiresome company, having the show of wisdom without the reality.

There are a couple of interesting things to note here. It seems to me, reading this out, that Thoth and Thamus seem to be arguing at least as much about what counts as memory as they are about writing and whether it will be a good thing or not.

Of course they are both right. Thoth is right because no matter what Thamus says, human societies that possess writing have, on the whole, much better historical knowledge than societies without writing, and much broader scientific and technical knowledge. On the other hand, Thamus is right, because few of us as individuals have memories that can compete with a Greek rhapsode or a Nigerian griot or a Serbian singer of tales. The individual memory is weaker; the system is stronger.

They sound to me a little like John Searle and Alan Turing arguing about whether a computer that can speak Chinese can legitimately be described as thinking — completely ignoring the revolutionary implications of the premise that we have a mechanical system that can speak Chinese in a way indistinguishable from a human being! Who cares whether it's “thinking” or not?!3

Thamus seems to me to be succumbing to what I think of as the John Searle fallacy. Because the human is the most important part of the system being described, or at least the part that most nearly resembles Thamus himself, Thamus identifies the capacities of the system with the capacities of the human component in exactly the same way that, in the discussions of the so-called Chinese Room, John Searle appears to be systematically unable to tell the difference between a computer system and a CPU.4

Thamus, on the other hand, is absolutely right in identifying a fallacy to which Thoth succumbs, a fallacy which some of us might not have expected to appear until much more recently, with the advent of data processing. Thoth said writing will make people wise, and Thamus said No, it will only make them appear well-informed: not the same thing.

I find that interesting because, for a long time, in teaching introductions to SGML and XML, I made the point that we want to build systems that are more useful and more intelligent, but until artificial intelligence bears fruit, if it ever does, we actually don't know how to make systems that are intelligent in any useful sense of the word. On the other hand, with descriptive markup, it's much easier to make systems that are well-informed. In computer systems as well as in human beings it's easy to confuse the two, and by well-informedness to give the impression of being intelligent.

Document grammars and entropy

There's another way to think about writing things down that may be worth spending a moment to consider.

In preparing for this conference I started reading the book that Ann Wrightson has been recommending for several years as providing the answer,5 Keith Devlin's book, Logic and Information, and then I digressed to read another book about information theory.6 Standard information theory as defined by Shannon shows us one way — surely not the only way, Devlin demonstrates that it's not the only way — to think about information flow, how to calculate the capacity of a channel, how to calculate the information content in an information source, how to do this mathematically.

I've been troubled by my readings in information theory because it seems clear that what descriptive markup does, what imposing the XML grammar on a datastream does, is reduce the entropy, which means it reduces the information content. How can any of us who care about information be happy about reducing the information content of the message?

I've had to work very hard to remind myself that information, in Shannon's theory, is effectively synonymous with entropy or disorganization; uncertainty on the part of the recipient, choice on the part of the sender. Reducing information content sounds alarming; reducing uncertainty sounds a lot better.

If the well-formedness rules of XML and the validation rules of our document grammar accurately describe the messages that will flow across that channel, then it's not a question of reducing the information content but a matter of more accurately estimating the information content. If there are true regularities in the information source that a document grammar allows us to capture, then we have a better understanding of the information source, which is good both from an engineering point of view and from a philosophical point of view. If the sender doesn't really have a particular choice, then it's better if the recipient knows that. The better we understand the nature of the signal, the better we will be able to distinguish information from noise at the receiving end.

There's a danger, if we prescribe too narrowly, or if we optimize the channel prematurely, saying, We'll provide easy ways to express all of the likely things, and these other things are so improbable that they are negligible. This is not unknown in the history of information theory. If we do that we have ruled out the possibility of certain surprises, and we run the risk of mistaking an unlikely message — a message that carries a lot of information precisely because it is unexpected — for noise, and discarding it, impeding our own ability to learn. That's another area where entropy could stand being reduced.

So: Writing things down about the nature of the information that flows is a good thing because all additional knowledge is good, and because it helps us engineer better.

Things we don't bother writing down

But there are some things which we are reticent about writing down.

Jon Bosak said the other day that there is a good reason that standard rules and procedures say a deliberative body should write down what it decides to do, and not why it decided to do it.7

One reason, of course, is that it's hard enough to decide what wording is going to go in the spec; if we also have to agree on why it should go in the spec, we will never finish.

Not everyone knows that when the Civil Rights of 1964 was passed by the U.S. Congress, the first draft forbade discrimination on the basis of race, color, or creed, and an amendment was offered adding sex to the list of protected categories. Many of us today, looking back, think of that as a good thing. But the amendment was not offered in that spirit. It was offered by southern congressmen who wished to reduce the pending bill to absurdity and ensure that it failed.

Should we reject their votes from the majority that passed the bill we approve simply because they voted for the amendment for what we believe to be the wrong reason? Should we reject the votes of those who voted in favor of the amended bill in spite of their misgivings about the inclusion in the amendment of sex, even though we think their misgivings were wrong? On the contrary. The first rule of any deliberative body, the most important skill of a Supreme Court Justice, as I think Justice William Brennan said, is to know how to count to five.8 [gentle laughter]

There are some things you really don't want to write down, because it's too much work and it's not worth it. Even if we do write down the rationale, there are limits — as Patrick Durusau was reminding me this morning after breakfast — there are very, very strict limits to our ability to constrain the interpretation of those who read the specs we write. We can try. But there are no guarantees. The ingenuity of readers knows no bounds. [gentle laughter]

Things that needn't be written down

There are some other things that we don't want to write down because they seem redundant. When you write rules for how working groups will conduct their meetings, no one ever suggests that we should make it a rule that the meetings should take place on Earth. We know they will. It would only raise questions in people's minds [great laughter] if we said so.

And there are some things I think have not gotten written down for that reason.

The SGML spec doesn't say anything normative about descriptive markup. It does have a description of descriptive markup and what some people call the SGML methodology, but it's in a non-normative appendix. The XML spec certainly doesn't tell you anything about how to design your vocabulary. Why?

One reason is [heavy sigh] even if the SGML and XML specs prescribed the correct design philosophy for markup vocabularies — let's assume we could all achieve enough hubris to believe that we could define it; most members of the working groups knew enough that they didn't want to try to nail it down for all time — even if they had tried, can you imagine achieving a normative definition of the difference between declarative semantics and imperative semantics? I can't. I pride myself on my spec draftsmanship, but that's not a definition I would want to make; it's not something that would turn into what the QA people would consider a testable assertion.

So nothing is said in the SGML and XML specs about that distinction. Why doesn't it trouble us?

It doesn't trouble us in part because many of us are convinced it doesn't matter whether we say it or not, it's like the law of gravity. Yes, it's true that it's better to have declarative semantics for your vocabulary than imperative semantics, but we don't need to tell you that because nature will teach you that. Nature will punish imperative semantics in ways that it doesn't punish declarative semantics.

Or ... ?

At least, that is the way I've always thought about it. But one of the things that started me wondering whether we've hit the right balance here was a talk I heard earlier this year from someone I like a great deal and who is very smart, but whose name I'm not going to mention because I'm about to slag him mercilessly; a talk in which this very smart guy talked with great pride about his role in the development of the XInclude spec.

Now, the XLink spec and the XInclude spec actually both talk about the same thing: I've got a resource here, and I've got other resources, and logically those other resources form part of a virtual resource that consists of the conjunction of this top-level resource and a bunch of others — the way images form part of an HTML document, or the way included external entities form part of an SGML document.

The problem, my colleague said, is that the XLink semantics are really hard to understand. Nobody can figure out what you're supposed to do. Which is one of the reasons you don't see a lot of conforming implementations of XLink: implementors look at it and say: “What am I supposed to do with this?” In this, at least, I agree with him: implementors have not figured out what to do in an XLink implementation.

The speaker was very happy, by contrast, with XInclude, which has a very clear semantics, he said — an XLink processor sees such-and-such an element, and it does such-and-such a thing — it has, that is, an imperative semantics.

In the analysis of the difference, my colleague was quite wrong. There is no difference in clarity. The XLink semantics are absolutely, perfectly clear: there is no possibility of misundersatnding. It's not that XLink is less clear than XInclude. The difference is that XLink carefully maintains a purely declarative semantics, and XInclude allows itself an imperative semantics.

At that point, I began to think, “Maybe the SGML old-timers among us didn't talk quite enough about the SGML methodology.” Because, when he said the XInclude spec was clearer, the earth didn't swallow him up; lightning didn't strike him. I was kind of disappointed. [laughter]

If, as is easily observable in many other places in data processing, many people find declarative semantics a little harder to grasp than imperative semantics, and XML becomes ubiquitous, then XML will be exposed to a lot of people who find imperative semantics easier to understand than declarative semantics, and if we are not careful, those of us who got into this business because of the advantages of declarative semantics will find that the barbarians have helped us achieve ubiquity of what we thought was going to be descriptive markup but what turns out to be only angle brackets; and that the infrastructure is built around systems that can't handle declarative semantics, that will only handle imperative semantics. And then where will we be? (Well, we'll be in a minority the way we've always been; but still.)

Cognition as a tool for defensive programming

I think in some way XML is all about getting things in writing in this way; understanding the data, knowing the regularities, knowing where it varies and where the variation is significant, is information, and when the variation is not significant, is noise. It's about our understanding, for a particular information source, the difference between noise and information.

Economically this makes sense: if you understand the regularities in the data and if you can enforce any restriction on the kinds of messages that can be sent, in particular the kinds of erroneous messages that can be sent, than you reduce the number of cases that programmers have to prepare for. You make it feasible for the amount of defensive programming that programmers are prepared to do, to actually meet the need. You increase the effectiveness of their defensive programming.

But I think the reason that a lot of us are so devoted to XML at a visceral, emotional level stems not just from its economic benefits but from the invitation it offers us to try to put down in writing what we perceive to be essential about the information we exchange and care about. By putting it in writing we reduce it from an infinitely subtle intangible to something still perhaps immensely subtle but infinitely more tractable. It's similar, in a way, to the transition between analog signals and digital signals, which Keith Devlin identifies with the act of cognitiion. Cognition is understanding an analog signal — an image, a situation — in a way clear enough to be able to put names to what counts for you, in your situation.

By putting it in writing, we externalize it, and we make it more malleable, we make it easier to share, easier for people we don't talk to, to read and understand. Edsger Dijkstra spent a lot of time wondering whether computer science was a discipline and thinking about the difference between scentific disciplines and guild-controlled crafts. The single best test he found was this: Are the results in this field published? Are they written down? Can people read them, or must you be initiated; must they be transmitted by oral tradition?9 By externalizing the knowledge, we make it easier for ourselves or for others to transform it; to transform it, for example, from a representation of what I think is essential to a representation of what you think is essential. We establish pathways, in that way, between different ways of thinking about things.

I suspect that future philosophers and historians of ideas may be alarmed to discover that, in order to trace the differences in relations between different ways of thinking about things in the 21st century, they are going to have to read and understand the ontological significance of XSLT stylesheets and XQuery transformations.

(But I notice that Allen Renear has already positioned himself to be in the forefront of this new school of philosophy!)

Getting it in writing

When we manage to get the key things down in writing without over-restricting things, without over-emphasizing the orderliness that we perceive, without filtering out signal unintentionally; when we get that down in writing, we are trying to make it possible for our systems of digital representation to call things by their true names.

The correct identification of what we see is one of the first stages of scientific knowledge. Linguists, trying to justify an interest in linguistic theory, frequently dismiss it as ‘botanizing’, but knowing what it is you're seeing is really a crucial first step. Some of us care about markup for that reason.

Calling things by their true names is also, as my poetry teacher in college taught me long ago, one of the ancient secrets of magic.10 Some of us care about it for that reason.

As Arthur C. Clarke taught us, that in turn means that calling things by their true names is one of the ancient secrets of creating advanced technology. [laughter and applause]11 Some of us care for that reason.

And my poetry teacher taught us that, whatever we may think of magic or advanced technology, it is one of the secrets of poetry.

And whatever the King Thamus may think, calling things by their true names will always be one step towards greater wisdom.

[applause, hollers]



Charlie Mingus, Mingus Ah Um (Columbia, 1959), reissued several times on LP and CD.

The liner notes (available on the Web at, show my memory was slightly off in some details: “Because of the success of this workshop, a Composer's Workshop was formed, in collaboration with Bill Coss of Metronome, that included Teddy Charles, John LaPorta and Teo Macero (who, as an A&R man for Columbia, arranged the date for this album). Mingus believes now that it got too far away from jazz — spontaneity — since almost all of the music was written. He remembers one rehearsal at which Teddy had left several bars open for blowing and everyone jumped on him with ‘Man, are you lazy? Write it out!‘“

Note that both sides of the tension are well represented here, the desire to have it written out, and the desire to leave some space open for the inspiration of the moment.


I quote from The works of Plato, tr. Benjamin Jowett, selected and edited by Irwin Erdman (New York: Modern Library, 1928). In the undated paperback reprint I am consulting, the passage is on page 323.


Alan M. Turing, “Computing machinery and intelligence,” Mind 49.236 (1950): 433-460; John Searle, “Minds, brains, and programs,” Behavioral and brain sciences 3 (1980): 417-457. These and other episodes in the sometimes amusing and sometimes alarming history of discussion of the Turing test are reprinted with commentary in The Turing test: Verbal behavior as the hallmark of intelligence, ed. Stuart M. Shieber (Cambridge, Mass.: MIT Press, 2004).


In fairness to Searle, I should point out that his paper includes a section designed to refute precisely this accusation. It is true that in my view he wholly fails to understand the nature of the objection or provide a persuasive response. But he does try.


See first of all Ann Wrightson, “Some Semantics for Structured Documents, Topic Maps and Topic Map Queries,” paper given at Extreme Markup Languages 2001 (available on the Web at, and this year her paper “Semantics of Well Formed XML as a Human and Machine Readable Language: Why is some XML so difficult to read?” (available at


Keith Devlin, Logic and information (Cambridge: Cambridge UP, 1991). The other book I have been reading is John R. Pierce, An introduction to information theory: Symbols, signals and noise, 2d rev. ed. (New York: Dover, 1980), which provides a good readable introduction to Shannon's information theory.


Jon Bosak, “The Universal Business Language (UBL),” Late-breaking news talk delivered at Extreme Markup Languages 2005, Montréal.


The maxim is attributed to Brennan by Anthony Lewis, “Privilege & the press,” New York Review of Books 52.12 (14 July 2005).


His concern with this question is so pervasive it's hard to choose just one place to point to, but my copy of his essays falls open by chance at an essay which makes this point quite explicitly: Edsger W. Dijkstra, “Craftsman or Scientist?” (EWD840) in Selected writings on computing: A personal perspective (New York: Springer, 1982), pp. 104-109. The essay was originally given as a Luncheon Speech at ACM Pacific 1975, in San Francisco.


Belle Randall's books of poetry include True Love (Seattle: Wood Works Press, 2003), Drop Dead Beautiful (Seattle: Wood Works Press, 1998), and The Orpheus sedan (Port Townsend, Wash.: Copper Canyon Press, 1980), but the book I know best is an earlier collection, 101 different ways of playing solitaire, and other poems (Pittsburgh: University of Pittsburgh Press, 1973).

So many stories involve the idea that knowledge of a thing's true name conveys power, often magical, that it seems dangerous to single any out. Sometimes the power is mystical, as in Kabbalistic tradition. Sometimes it is wholly mundane, as in the science fiction writer Vernor Vinge's short story “True Names” (first published in 1981, reprinted in Vinge's True names ... and other dangers, New York: Baen, 1987). After the talk, Simon St. Laurent observed that in some tellings, knowledge of the true name can have effects we might find deplorable (e.g. Arthur C. Clarke, “The nine billion names of God”, first published in 1953 and reprinted several times, most prominently perhaps in The nine billion names of God: the best short stories of Arthur C. Clarke, [New York: Harcourt, Brace & World, 1967]). Simon concluded with the plea “Save the universe; don't call things by their true names.”


In the 1973 republication of his Profiles of the future (New York: Harper & Row, 1973) Clarke added to the essay “Hazards of prophecy: The failure of imagination” (originally published in 1962) the observation that “Any sufficiently advanced technology is indistinguishable from magic,” giving it the name ‘Clarke's Third Law’.

My joke relies only on the fact that indistinguishability is a symmetric relation.

Getting it in writing

C. M. Sperberg-McQueen [World Wide Web Consortium, MIT Computer Science and Artificial Intelligence Laboratory]