Archive for the ‘Recreations’ Category

« Older Entries

Mystery and mathematics

Tuesday, February 2nd, 2010

[2 February 2010]

Lately I’ve been spending some time of an evening reading E. T. Bell’s classic collection of biographies of mathematicians: Men of Mathematics (1937; rpt. New York: Simon and Schuster, 1985). (As the title suggests, Bell is thoroughly pre-feminist; a collection called Women of Mathematics has been published more recently, which may be intended as a kind of pendant to Bell, though sadly it’s nowhere like as much fun to read; its authors are for the most part better historians and much less opinionated.) And something rather puzzling caught my eye the other evening.

Bell writes (p. 357 of the Simon and Schuster paperback reprint) in his sketch of the Irish mathematician William Rowan Hamilton:

So long as there is a shred of mystery attached to any concept that concept is not mathematical.

Granted, Bell was probably tired of having to tell generations of incredulous undergraduates that there is nothing especially imaginary about imaginary numbers; one might grow peevish on the subject over the years. But still: did Bell seriously believe that the natural numbers (say) are not mysterious?

Can anyone not dead to all sense of wonder contemplate the commutative property of integer addition without feeling themselves to be in the presence of mystery?

Posted in Recreations | 4 Comments »

Thought for the day

Tuesday, January 19th, 2010

[19 January 2010]

Not quite heard in conversation: “You will never gain full mastery of any tool until you have misused it.”

Posted in Recreations, Uncategorized | 1 Comment »

Bare-bones TEI

Wednesday, January 6th, 2010

[6 January 2010]

The markup vocabulary defined by the Text Encoding Initiative is, for good and sound reasons, rather large and in some ways rather complicated. From time to time, however, it’s useful to have a radically cut-down version of the TEI vocabulary. For people just learning TEI markup (to name just one instance), a cut-down version can simplify initial training and make the TEI feel a little less intimidating.

Many people use TEI Lite, which is much smaller than full TEI. But for some work I’m doing with Yves Marcoux and Claus Huitfeldt, we felt it would be handy to have an even smaller subset of TEI to work with. Years ago (1994), I defined a profile of TEI called ‘Bare Bones TEI’, intended not so much for serious use as for training and for thought experiments.

I had long regarded the full details of bare-bones TEI as lost to history: the documentation has been preserved by Robin Cover at the XML Cover Pages, but it didn’t include the DTD modification file showing the precise changes from the then-current TEI DTD. I had tried a few times, searching both the Web and my hard disk, to find the original data, but had had no luck. But the other day, for reasons I don’t think I can explain, an attempt at one more search eventually found an old copy of the documentation, the modification files, and the full DTD for bare-bones TEI.

I’ve now translated the original documentation to XML, added updated links to the various DTD files, and added parameter entities to the DTD to make it work both for SGML contexts and for XML. The documentation for Bare bones TEI is now available on this site, as is the modified DTD.

The current version of the bare-bones DTD is based on TEI P3, and the translation to XML loses a small amount of information involving the pb (page break) element. Eventually, perhaps, I’ll apply the bare-bones customization to TEI P5 and produce an updated version of the schema and documentation.

Note: in searching for Bare-bones TEI on the TEI Consortium site just now, I discovered that someone has produced a similar profile, called ‘Bare TEI’. [Further research shows that although the page on customizations does not identify the authors, the work was done originally by Laurent Romary and later edited by Syd Bauman, Lou Burnard, and possibly also Sebastian Rahtz.] This may be worth exploring, for those seeking a minimal profile of TEI. Unfortunately, I haven’t found any usable documentation for Bare TEI, so I don’t know the design principles that govern it, and the DTD is full of undefined ghost elements (or ‘zombies’), which renders it unfortunately cumbersome in a syntax-directed editor. So for now I’m sticking with bare-bones TEI.

Posted in Recreations, TEI | 7 Comments »

Philosophers make quick keyboardists

Thursday, December 17th, 2009

[17 December 2009]

A mnemonic for ACL2 induction

Lately I’ve been spending time working through a lot of exercises in ACL2. As a way of helping the user internalize the requirements for successful induction, several exercises ask for an explicit reformulation of a problem in terms of the ACL2 induction principle.

Don’t worry: I don’t want to try to explain the ACL2 induction principle here. It suffices for present purposes to observe that a fully explicit application of the ACL2 induction principle requires that you write down a number of things; you, dear reader, don’t need to understand what they are, only that they exist and need to be specified:

  • φ, the formula being proved
  • m, the measure to be used when computing the ‘size’ of a particular instance of the formula
  • qi (for 1 ≤ i ≤ k), the conditions which determine the different induction steps: one induction step for each qi
  • k, the number of induction steps (and thus of conditions)
  • σi,j (for 1 ≤ i ≤ k and 1 ≤ j ≤ hi), the substitutions applicable to condition qi; each condition qi may have up to hi hypotheses and corresponding substitutions
  • hi, number of induction hypotheses for each induction step qi
  • the measure conjectures for the case: (a) that the measure given always produces an ordinal value, and (b) that the measure decreases on each recursive call (i.e. in each induction hypothesis)

After a while, my evil twin Enrique got tired of watching me flip back and forth between the statement of the problem I was trying to solve and the page that showed all the things that needed to be written down; he said “Haven’t you memorized that list yet?” “No,” I said. “It’s not that simple a list, is it?”

“Sure it is,” he said. “Just use a mnemonic to remember it. The full list, with all subscripts, is

φ m, qi ≤ k, k, σi, j, hi, m c

“So just remember

Philosophers make quick keyboardists; strength in judgment helps improve mental capacity.

“Or if you can remember the subscripts by yourself, and just need (φ, m, q, σ):

Philosophy multiplies quizzical subtleties.

“Easy, see?”

Sometimes I think Enrique has too much time on his hands.

Tags: ,
Posted in Recreations, formal methods | No Comments »

Metadata and search - a concrete example

Tuesday, August 18th, 2009

[18 August 2009]

Here’s a concrete example of the difference between the metadata-aware search we would like to have, and the metadata-oblivious full-text search we mostly have today, encountered the other day at the Balisage 2009 conference in Montréal.

Try to find a video of the song “I don’t want to go to Toronto”, by a group called Radio Free Vestibule.

When I search video.google.com for “I don’t want to go to Toronto”, I get, in first place, a song called “I don’t want to go”, performed live in Toronto. When I put quotation marks around the title, it tells me nothing matches and shows me a video of Elvis Costello singing “I don’t want to go to Chelsea”.

It’s always good to have concrete examples, and I always like real ones better than made-up examples. (Real examples do often have a disconcerting habit of bringing in one complication after another and involving more than one problem, which is why good ones are so hard to find. But I don’t see many extraneous complications in this one.)

Posted in Balisage, Conferences, Recreations | 4 Comments »

Mainframe terminal rooms and the oral tradition

Tuesday, July 7th, 2009

[7 July 2009]

A number of XML experts I know use Emacs for editing XML, employing either James Clark’s nxml mode or Lennart Staflin’s psgml mode. But few people who don’t already know Emacs are eager to learn it.

My evil twin Enrique suggested a reason: “In the old days,” (he means thirty years ago, when he first learned to use computers), “using a computer mostly meant using a mainframe. Which meant, on most university campuses, using a public terminal room. Which meant there were usually other people around who might be able to help figure out how to make the editor do something. Emacs was able to spread widely in that culture because the written documentation was not the only available source of information. (Did Emacs even have written documentation in those days?) Emacs, and a lot of other tools, were propagated by oral tradition.

“Nowadays, however, the oral traditions of the public terminal room are mostly dead. What the user cannot figure out how to use from the user interface and (perhaps) a glance at the documentation, might as well not be in the program. Fewer and fewer users will trouble to learn Emacs.

“I predict that when the people who first learned computing in a mainframe terminal room are dead, Emacs will be effectively dead, too. Its natural method of propagation is by looking over someone’s shoulder at what they are doing and asking ‘How did you do that?’ That doesn’t happen when computing almost always happens in private places.

“R.I.P., Emacs,” he intoned mournfully. “And probably TeX and LaTeX, too.”

“Well, hang on,” I said. “Neither Emacs nor TeX is dead yet.”

“Maybe not, but it’s only a matter of time. They’ll end up in the Retro-Computing Museum.” I could have sworn I saw a tear in his eye.

“But, you know, it’s only a matter of time for all of us. And besides, you’re wrong in at least some ways. I did indeed spend the first few years of my computing life haunting university terminal rooms. I got a lot of help from other people, and I passed it on. But I didn’t use TeX or Emacs until years later. The oral traditions of the terminal room, if they ever actually existed, had nothing to do with it. Both Emacs and TeX are perfectly capable of acquiring new users without oral transmission.”

He looked up. “You mean, there’s hope yet?”

“There’s always hope. But no, I’m still not going to help you debug that self-modifying 360 Assembler program you brought over. I’ve got work to do.”

Posted in Data longevity, Recreations | 3 Comments »

For collectors of headline ambiguities …

Wednesday, April 22nd, 2009

[22 April 2009]

Linguists (and others) like to collect cases in which the compressed, telegraphic style of newspaper headlines lead to unexpected syntactic ambiguities.

The Albuquerque Journal and the Santa Fe New Mexican both carried stories yesterday about the results of a new University of New Mexico study on the incidence of spinal injuries in the U.S.

I showed them to Enrique, who glanced at the headline in the Journal:

Paralysis More Widespread Than Thought

and asked “When did the Albuquerque Journal start covering W3C and ISO Working Groups?”

Posted in Recreations, Standards development | 1 Comment »

Enrique and the printer

Wednesday, February 18th, 2009

[18 February 2009]

Enrique isn’t speaking to me just now.

He phoned this morning, fuming. “I installed some new OS update the other day, and now my printer won’t print.” “I’m sorry to hear that,” I said. I was, too: when Enrique’s printer doesn’t work, he always wants to use mine. “Did you try to fix the problem?” “Well, I went to the Web and found some advice to try deleting the printer and re-adding it. So I deleted it. And now the [expletive deleted] machine can’t see the printer at all!” “Ouch,” I said, wondering whether the toner we have on hand would get us through the week, if Enrique descended on us with hundreds of pages to print. “So I ran Software Update again, and it took forty-five minutes to download yet another security update for the OS. And it still couldn’t find the printer. So then I went to the Apple site and downloaded the packet of HP printer drivers … and it’s still not finding the driver.“

“Is the USB cable seated securely?” “What kind of amateur do you take me for? Of course. I checked, it’s secure both at the machine end and at the printer end.“

“Did you unplug and replug the power cord, too?”

There was a brief pause, before the call was cut off. Like I say, he’s not talking to me today. I’ll try to use the quiet time to get some other work done.

Tags:
Posted in Recreations | No Comments »

Writing tight

Thursday, November 13th, 2008

[13 November 2008]

Dimitre Novatchev has called attention to a recent question on the
stackoverflow programming Q and A web site:

I have an XPath expression which provides me a sequence of values like the one below:

1 2 2 3 4 5 5 6 7

It is easy to convert this to a set of unique values “1 2 3 4 5 6 7″ using the distinct-values function. However, what I want to extract is the list of duplicate values = “2 5″. I can’t think of an easy way to do this. Can anyone help?

Dimitre’s solution is beautiful and concise: 21 characters long (longer if you use variables with names longer than singler characters), and well worth the five or ten minutes it took me to work out why it works. I won’t explain it to you, dear reader; you deserve the brief puzzlement and Aha-moment of understanding it.

Despite being terse, it’s not the kind of thing you’d enter in an Obfuscated XPath contest, it just uses an idiom I haven’t seen before. I’ll see it again, though, because I’ll use it myself; as I say, it’s beautiful. (I do confess to a certain curiosity about how he would modify it if, as he says, efficiency needed to be addressed.

Dmitre gets my vote for this month’s best programming-language application of Strunk and White’s rule: “Omit needless words!”

Posted in Recreations, XML | 1 Comment »

Thought for the day

Thursday, August 21st, 2008

[21 August 2008]

If we call Courier and similar fixed-width fonts “monospaced”, shouldn’t we be calling Garamond and similar variable-width fonts “polyspaced”?

Posted in Recreations | 1 Comment »

« Older Entries