- From: David Woolley <david@djwhome.demon.co.uk>
- Date: Sat, 20 Nov 2004 12:40:19 +0000 (GMT)
- To: www-svg@w3.org
> I agree semantics would be extremely useful in some use contexts, e.g. if > people are intending to use SVG to replace HTML + CSS, in others, I'm not so I suspect that is a major growth area for SVG, especially in the mobile market, where the lack of inclusion in out of the box Windows or Windows Update is not a blocking factor, and there isn't a large body of HTML hacks for cut and paste coders. My impression is that many commercial web designers only think visually, and therefore try to use HTML+CSS as a page description language, not a document language.[A] It is the HTML type uses that tagged PDF addresses, but there is a whole spectrum of uses of (near) final form graphical presentation languages, nearly all of which have semantics attached to them that is deeper than what is represented in the graphics metafile. Technical diagrams often have very strong topologies that are lost in low level graphics languages. Business graphics have underlying real data sets. Maps have strong topologies, but final form graphics may end up separating labelling from symbolic and topographic layers. > sure. Ultimately, SVG could be considered accessible without semantics. > Users extracting meaning from visual parsing of the displayed document have With suitable AI, so would JPEGs. Also, the whole point of most use of graphics is not the graphics themselves but that they make it easy to convey information (or, in the commercial world, emotional messages[B]). They are also used to achieve instant recognition (logos, and branding in general). If accessibility depends on describing the detailed structure, that benefit is lost even more than if the information hadn't used grphics in the first place. > learnt to infer meaning from various visual attributes, the same goes for This, itself, is a serious accessibility issue. There are many users, especially the elderly, and those in their middle age that haven't been brought up with computers, who haven't learnt, or can't[C] learn, the many graphical metaphors used on the modern web, even when observing them through their eyes. > pretty much any form of communication. Therefore, provided those visual > attributes can be conveyed non visually, there's no reason why a blind user Semantics helps not just the blind and can help ordinary users. In particular, it allows machine processing (which may have negative commercial impact, of course). > couldn't associate meaning with the attributes. Using current output > modalities that are sequentially based, such as speech or Braille, this will One has to serialise even bitmap graphics for computer uses, but proper encoding of semantics doesn't constrain one to linear presentations. If one looks at an old feature of PDF, called bookmarks in PDF terminology, but I would call it an outline tree. The well marked up HTML and CSS specifications allow this to be derived by the html2ps tool used to set the PDF versions of those specifications. The result is that you can quickly navigate the document structure. This use of proper markup is also used by some minority HTML browsers. Another possible use of good semantic markup would, in the case of a web application, be the ability to overlay standard forms of user interface controls onto the custom designed controls, so that people without a long education in web design conventions didn't need to decipher the design metaphor to find and use them. > be a long and tedious process that would make SVG, whilst accessible, not > very usable, so semantics can play a big part in boosting the usability of > SVG. > > As an aside, it's down to the ua and authoring tool vendors to ensure their > products are 508 compliant, but having accessibility included as part of the > spec would help tremendously in this effort. 508 provides a regulatory environment which forces businesses to take account of such issues, but it is not the only such legislative framework and the need of users (if not authors) would exist without it. Other parts of W3C have typically taken more than a bottom line view to what goes into specifications, e.g. features that conflict with the creation of a world wide web are discouraged, even though commercial authors like them, and few commercial sites want anything but incoming links to home pages. The problem with SVG is that, to a large extent, it "externalises" the issue by saying you should use a higher level markup and transform client side, but ignores the reality that most authors will just send the SVG and in HTML replacement applications, will likely have not authored it with tools that represent the semantics, or failed to use the relevant capabilities of such tools. The HTML+CSS model is to decorate a more semantic model with presentational details. The tagged PDF approach is to decorate a presentational form with semantic data. To a large extent, SVG is presentation alone. That's almost OK as a technology, but the reality is that SVG is being developed as a product (in my view, as a way of competing with Flash[D], even though Flash now has SVG support), and users are using it as a single technology solution. [A] I think this is largely because commercial web pages are, very often, advertisements of the non-informational type and are created by people with visual arts training, not with verbal communication training. [B] These are not good candidates for semantic markup as they are often not objectively justifiable, so cannot safely be stated explicitly. [C] Reasons, in the elderly, can vary from a fairly common fear of making mistakes and getting lost, to degenerative diseases of the brain. [D] People will argue that SVG is used for more technical graphics than is Flash, but I think that is more to do with how Flash is marketed and I think the big growth area in SVG will be commercial art, not technical uses.
Received on Saturday, 20 November 2004 12:41:40 UTC