From: Matthew Slyman <whatwg@aaabit.com>

Date: Fri, 23 Sep 2011 21:10:59 +0100

Message-ID: <20110923211059.10412q5cn8lh0moj@ares.krystal.co.uk>

To: Ian Hickson <ian@hixie.ch>

Cc: whatwg@whatwg.org, public-webapps@w3.org

Date: Fri, 23 Sep 2011 21:10:59 +0100

Message-ID: <20110923211059.10412q5cn8lh0moj@ares.krystal.co.uk>

To: Ian Hickson <ian@hixie.ch>

Cc: whatwg@whatwg.org, public-webapps@w3.org

Matthew Slyman, M.A. Computer Science (Camb) -- Quoting Ian Hickson <ian@hixie.ch>: > > We took it out because it was just far too complicated a solution to solve > far too narrow a set of use cases. > > However, there is a lot of ongoing work in this area of research, > especially currently in the public-webapps@w3.org group. I encourage you > to bring up the suggestion there. Unfortunately, coming up with a > declarative solution whose cost-to-usefulness ratio is good enough has > proven over the years to be a rather elusive goal. > I find this surprising. Unless of course you're trying to create a tool to do everything (in which case you're diving head-first down a rabbit-warren), or otherwise, have already tried that and decided it doesn't work, and therefore decided that it's not worth attempting a solution to any part of this problem. Let's address another potential misconception at the same time. I recently dug up an old archive message from 2004/2005 in which some fellow was talking the repetition model down on the basis that "repetition would be programming and declarative models aren't meant to do programming" or something to that effect. Repetition isn't truly programming if it isn't Turing-complete. But I get the point, and I would NEVER ask for a declarative solution that would be Turing-complete. Let's look at a case study or two: ===Chemical formulae===: These have had a repetition model for a long time now, which is very simple but very powerful. Like so: Ca(OH)2 [subscript 2 - put superscript figures in for charge if you want.] Nobody has a problem with this. It does the job and it's very powerful. Just powerful enough, yet not so "powerful" that you end up with 20 different ways to write the same chemical formula (the system is sufficiently restrictive to enforce a common system of notation). It strikes the balance perfectly, and forms a perfect demonstration of the relative advancement of chemistry as compared with many other sciences. The combination of power and simplicity in this system of chemical notation (which closely resembles the basic HTML5 "Repetition Model") enables the world of chemistry to get on with their real work without worrying too much about the art of notation, and enable chemists to find prior art easily. ===Linear equations===: A similar case could be made for these. They're a separate class of problems from the much larger set of problems that can be tackled with mathematics in general. You shouldn't put the folks that need real power and freedom in a strait-jacket by forcing them to work with a system designed for linear equations only. Likewise, you shouldn't burden and befuddle the novices and the folks that just need to get a quick linear equation job done, by forcing them to work with a generalised mathematical tool that they're just not trained to handle, and will never be confident using. ===Classes of problems===: For many problems, there is such a thing as "too much power". Let's please recognise that we're dealing with two distinct classes of problems here. There is a class of problems that requires a similar approach/solution to what we see in chemical notation (where one only requires a contiguous repetition of a block of HTML, which may or may not include repeatable subgroups), and another separate and much larger class of problems that requires the greater power available in a programming language. The correct solution for the former is a declarative solution like the basic HTML5 Repetition Model. The correct solution for the latter is Javascript or something similar. ===CONCLUSIONS===: We need a declarative solution for HTML repetition, the same way Chemists need a declarative solution for repetition of chemical formulae. Please reinstate the basic HTML5 Repetition Model. The system design as it stood just a few months ago was excellent in my opinion, and not at all in need of major revision if any. -- Matthew Slyman, M.A. Computer Science (Camb)Received on Sunday, 25 September 2011 13:18:04 UTC

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