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SVG Tiny 1.2 CR2006-08-10: 7.7 Constrained Transformations

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sun, 15 Oct 2006 16:03:14 +0200
To: www-svg@w3.org
Message-Id: <200610151603.14819.Dr.O.Hoffmann@gmx.de>

Hello, 
two more comments about the 'Constrained Transformations' chapter:

1. In 7.7.3 it is noted:

"Similarly, we use the following notation for the transform defined by the 
transform attribute on the given element with identifier 'elt'. 
Txf(id)"

Is this correct/intended or should it be

"Similarly, we use the following notation for the transform defined by the 
transform attribute on the given element with identifier 'id'. 
Txf(id)"

or 

"Similarly, we use the following notation for the transform defined by the 
transform attribute on the given element with identifier 'elt'. 
Txf(elt)"

?



2. In 7.7.5 several times the inverse of a matrix is used.
In most cases I can visualise the visible effect of the 
TransformRef/ref(svg)/ref() value, but in the formal description 
it is missed what happens, if the inverse of the matrix does not
exist. In most ot these cases it is anyway possible to get
the described effect, but of course not using the not existing 
inverse matrix. Another method has to be used, what is possible
with the given information in a SVG document, but not described.
Currently I have only one example containing animation with a case 
without an inverse, I cannot visualise the visible effect of TransformRef
in a well-defined way (infinite types of behaviour are consistent with
the description in this case).
Therefore a description is needed for practical reasons too,
not just for formal mathematical reasons, what happens, if
the inverse does not exist, to provide well-defined behaviour.
Another (not my) problem may occur to get the correct visual
effect for implementors in general, if the inverse does not exist.
Received on Sunday, 15 October 2006 14:05:51 GMT

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