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27354Custom Namespace Extension (was Re: namespace question)

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  • Doug Schepers
    Mar 12, 2003
      Thanks for the quick reply, Tobi. That particular animation is one of the
      earliest I'd seen of SVG (lo, these many years ago), and I found it fun and
      exciting.

      However, this is somewhat different than what I'm doing. You are using a
      predefined NameSpace, RDF, and limiting your meta-data to an isolated
      section of the SVG. What I wish to do is create a custom NS, and apply it to
      pre-existing SVG elements interspersed thoughout the document:

      <line id="line_1_2" x1="0" y1="3" x2="15" y2="50" mcns:category="5"/>
      <text id="text_5" x="10" y="50" mcns:association="line_1_2">Sample</text>

      I have around 15 of these custom Attributes (so far), and no custom
      Elements (yet); each can be applied to any of the following Elements:
      <text>, <line>, and <use> (possibly more, as development continues).

      My primary references at this point are:
      W3 School DTD Tutorial
      http://www.w3schools.com/dtd/default.asp

      SVG1.1 Spec, section 23.5 "Adding private elements and attributes to the
      DTD":
      http://www.w3.org/TR/SVG11/extend.html#PrivateElementsAndAttribute

      My questions are:
      1) Do I have to declare an ENTITY for each Attribute, for each Element? Or
      can I group them together in one generic ENTITY? DO I need an ENTITY at all,
      if I only have Attributes and no Elements?

      2) Do I have to make a seperate ATTLIST for each Attribute, for each
      Element? Or can I declare each Attribute once, and refer to that definition
      in the ENTITY(s)? Does each Attribute have to have its own ATTLIST, or do I
      list all the Attributes under one ATTLIST?

      3) How do I determine whether I should use CDATA or PCDATA; that is, when do
      I want to parse the Attribute value? Some of my Attribute values are
      enumerated [(left|right|top|bottom)], but some can take values defined by
      the user at runtime. Presumably the former would use PCDATA, and the latter
      CDATA? if the user-defined ones are constrained in their format to use the
      same alphanum charset as XML IDs, are they parsed? Conversely, are there any
      restictions on non-parsed Attribute values to which I would need to
      constrain users?

      4) None of these Attributes currently affect how the SVG is rendered; they
      are meta-information for use in assigning tooltip labels, establishing
      complex relationships between elements (IDREF and IDREFS), and tokens for
      indicating how the code should treat each Element. Is there any way I can I
      use these Attributes as style classifiers, say? So that, for example, all
      lines of 'mcns:category="5"' would be red, and all of category 3 would be
      green? And if this can't be done in ASV3, is it at least theoretically
      possible? This question is not really a high priority, but it would be neat.

      5) Currently, I'm designing for ASV3/IE6, which is pretty forgiving of my
      using a custom NameSpace, in terms of getting and setting Attributes. But
      are there considerations to other renderers I should be aware of? Obviously,
      I'm using g/setAttributeNS exclusively, now. I'd hate to build this app only
      to have it end up a one-trick pony.

      I must confess, this is peripheral to the application, and I wish only to
      know as much as I need to in order to make my SVG valid, so I don't really
      want to read a book on the subject. A pointer to an online tutorial or an
      example would be great.

      Sorry for the long and possibly OT post.

      Many Thanks-
      Doug


      Tobias Reif wrote:
      > Doug
      >
      > > I've also been embedding "meta-information" in one of my SVG
      > apps, in much
      > > the way that Jon has, below. [...] But now I want to define
      > > the namespace attributes, to make it "legal" and valid, if possible.
      >
      > Check the source of
      > http://www.pinkjuice.com/svg/svgz/layout02.svg
      >
      > HTH,
      > Tobi

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