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The world according to Sven-S. Porst

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Semantics

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Mark Pilgrim rants a little about gerbils and semantics, providing plenty of links and points. Most notably he warns against overstating the benefits of using any of validating web pages, CSS or semantic markup. Just the fact that you formally manage to churn out conforming web pages, doesn't mean they're any good.

I don't really know much about the 'semantic markup' business, but as far as my understanding goes, the main point is that your markup should attempt reflect your document's structure.

This is pretty obvious for things like headings – tell your browser it's dealing with a heading instead of telling it to use Zapfino at a certain size for those chunks of text. Easy. This situation seems pretty much win-win to me. I don't have any extra effort as I'd have to chuck in some markup for the heading anyway to specify the font. In fact, I may even save some work as the heading tags are particularly short. In addition my reader may enjoy the benefits of this markup if his or her browser can automatically generate an outline from the heading tags I used (not that I've ever even seen this rather trivial application of the markup in client applications).

So here, semantic markup – or whatever I think semantic markup is – works pretty well. To me that win-win aspect seems important. It isn't any extra work. You won't go insane by having to put zillions of extra tags in your documents. Just a different tag.

My impression is that advocates of semantic markup sometimes want to go too far: include markup for every abbreviation, state the significance of every single word by inserting extra tags. This usually means a lot of extra work for little to no benefit to the reader. So there's very little incentive to do it – in particular if the tags aren't generated automatically. If your objective is to write a text, you probably don't want to waste your time typing tags.

Let me digress to a topic that I am naturally interested in: mathematics and electronically writing about it in (La)TeX. TeX is frequently touted as an example for markup. I don't think (anymore) that's correct. Firstly because technically the examples aren't in plain TeX but rather in LaTeX. In LaTeX, to start a new section you simply type \section{Semantics} and there you go: a new paragraph, a heading, a bookmark in the PDF file, updated running headers, table of contents entry – whatever. If you don't like the looks of it you load a different document class and your heading will look differently. A bit like loading a different style sheet in HTML.

This kind of markup is nice. You can focus on what you're writing and don't have to worry about the looks. But what happens where the real work gets done? In formulæ? Consider the following:

xi

A pretty harmless expression that requires nothing but the obvious x^i in TeX's math mode. And that's nice as well. Probably the most efficient way to get the desired display. It's not, however, fully marked up. This expression could be anything. Some real number x taken to the real i-th power, some complex number x taken to the power of the imaginary unit, some group element x taken to then integer i-th power, the i-th co-ordinate, the i-th cartesian power of a set x – and so on. The notation can mean almost anything and all we use the TeX command for is to ensure it is displayed in the way we want it to look – its meaning hopefully being clear from the context.

I think that's a good thing. If people were seriously into marking everything up, they'd precisely state what each of the letters is and what the raising of the second letter means. Surely that would have certain benefits as changing a document to the notation that you personally favour would only cost a click of your mouse. On the other hand, however, document creation would probably grind to a halt as that approach would have an unacceptably low content-to-markup ratio.

An interesting question to ask in an all-marked-up world would be how that precious hobby of mathematicians known as abuse of notation is handled. Often people use notation that omits certain details. While those details may be important for comprehensive markup, their omission may actually make the expressions more human-readable and even comprehensible as the reader's attention is shifted to the significant parts rather than caught in notation.

Another question is how MathML fares. I haven't looked into it thoroughly. But my fear that it forces you to use all-markup all-the-time seems not to be true. There seems to be an option for presentational markup as well. Both of them look rather scary, though. Just check page 10 of this introduction for an example. It doesn't look like a winner to me. It tries to do too much.

And for good taste, let me show off what was forwarded to me from an unknown source:

August 30, 2003, 3:04

Tagged as TeX, zapfino.

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