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From Jeremias Maerki <...@jeremias-maerki.ch>
Subject Re: Namespaces for fop extensions
Date Sun, 07 May 2006 10:10:44 GMT

On 06.05.2006 22:17:37 Simon Pepping wrote:
> On Sat, May 06, 2006 at 11:31:38PM +0800, Manuel Mall wrote:
> > I wonder if we should agree on some guidelines for the use of namespaces 
> > (namespace prefixes) for extensions. I am thinking along the following 
> > lines:
> > 
> > The namespace "http://xmlgraphics.apache.org/fop/extensions" (common 
> > prefix "fox") is reserved for generic extensions to FOP supported 
> > across all (e.g. if handled by layout) or most renderers.
> > 
> > Extensions specific to a particular renderer and / or extensions which 
> > constitute a rendering hint (e.g. render this image as a grayscale) 
> > should be in a renderer specific namespace. That namespace name is 
> > formed by appending the common renderer acronym to the above generic 
> > extension namespace, e.g. 
> > http://xmlgraphics.apache.org/fop/extensions/pdf or 
> > http://xmlgraphics.apache.org/fop/extensions/pcl or 
> > http://xmlgraphics.apache.org/fop/extensions/afp. At the same time the 
> > usual prefix for those extensions would be just the renderer acronym.
> This sounds fine to me.


> > Even if the same type of rendering hint can be used by different 
> > renderers they still should be in separate namespaces as this allows 
> > the user control over behaviour on a per renderer basis without 
> > changing the fo file. For example lets assume we want to support image 
> > conversion hints which allows tuning of the image output format. 
> > Instead of having <fo:external-graphic 
> > fox:output-conversion="grayscale" src="xyz.png" /> I would recommend to 
> > use render specific hints like <fo:external-graphic 
> > afp:output-conversion="grayscale" pcl:output-conversion="bitmap" 
> > pdf:output-converion="jpeg" src="xyz.png" />. This may not be a good 
> > example but I hope it illustrates what I am trying to achieve.
> I see what you are trying to achieve. Wouldn't users find this
> overdone, and wonder why they cannot do with a single hint for all
> renderers? Or would a single hint just not work?

From a power-user's perspective the flexibility is welcome, especially
since not every renderer provides the same kind of conversion methods
and the same quality for each kind. For normal users, it may be overkill
and may only produce confusion, but on the other side, they may never
need that. Maybe we need both: fox and output-format-specific. The
renderers first inspect the fox hint and then look for a
renderer-specific hint.

Jeremias Maerki

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