- From: Chris Lilley <chris@w3.org>
- Date: Thu, 6 Apr 2006 13:53:22 +0200
- To: www-svg@w3.org
- Cc: Bjoern Hoehrmann <derhoermi@gmx.net>
Hello www-svg, > * Chris Lilley wrote: >>BH> http://www.w3.org/TR/2005/WD-SVGMobile12-20050413/struct.html does >>BH> not seem to include adequate requirements for vendor-specific >>BH> presentation attributes even though these apparently may be defined >> >>We are unable to discover anywhere in the specification that allows a >>custom, vendor-specific property to be defined. > > Are presentation attributes and properties the same thing? If not your > response seems a bit odd. They are related, but not the same thing. Properties are defined in the specification. New properties cannot be defined by the document author. (The requirements were we to add such a facility in the future were listed later in my original reply). Presentation attributes are one way to set the value of a property. There are other ways, for example using CSS stylesheets, or using the DOM. Which attributes are presentation attributes is defined in the specification. New presentation attributes cannot be defined by the document author. Attributes are, well, attributes. As long as they are not in the default namespace on svg elements, new attributes may be defined by the document author, and in fact this is commonly done. However, that does not make them presentation attributes and does not produce any link between that attribute and any new or existing property. See the section 'Foreign namespaces and private data' in the Extensibility chapter for details. >>BH> and implemented in conforming implementations. Please change the >>BH> draft such that either this is not allowed (e.g., only "attributes" >>BH> not "properties" may be used for extensions) >> >>This is the current situation. Furthermore, such attributes must be >>qualified, if they are on an element which is in the SVG namespace. So, >>we believe the specification to already be clear in this regard. >> >>BH> or such that it is >>BH> required that such properties must conform to >>BH> http://www.w3.org/TR/CSS21/syndata.html#q4 >> >>Although interesting, and perhaps something to consider for a future >>specification, such a method would require a means to declare: >> >>- that the attribute is in fact a property >>- whether it is inheritable or not >>- the value space >>- use of percentages >>- computed value > > So you are saying What we are saying is listed above. What you are saying is below, and does not correspond to what we are saying since you did not understand the difference between properties, presentation attributes, and attributes. Please review these definitions; they are connected, but not identical by any means. > that it is neither possible nor allowed to come up > with presentation attributes correct > like a:adobe-knockout you do not demonstrate that this is a presentation attribute. Its an attribute; its not in the svg namespace or the default namespace. > and corresponding properties like adobe-knockout, you gloss over how this is a 'corresponding' property. > and that this is obvious from the current draft. Yes. > I don't see evidence for any of that, so this does not > address my concern at all. We do not find your argument convincing. You refer in vague terms to creating presentation attributes and creating 'corresponding' properties, but do not explain how that would be possible. We have explained both that it is not possible, and also what would be required to make it possible in a later version of the specification. In CSS stylesheets it is certainly possible to reference vendor-specific properties, such as -vendor-specific but SVG Tiny 1.2 does not allow author stylesheets. CSS is also silent on how the initial value, the inheritability, the computed value,and the handling of percentages is communicated to the application. In SVG Full, author CSS stylesheets are allowed, and thus vendor-specific properties would be allowed also, but there is still no way, in the current specification, to create a mechanism that would allow these properties to be associated with a corresponding attribute such that the attribute became a vendor-specific presentation attribute. -- Chris Lilley mailto:chris@w3.org Chair, W3C SVG Working Group W3C Graphics Activity Lead Co-Chair, W3C Hypertext CG
Received on Thursday, 6 April 2006 11:53:26 UTC