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Subject: RE: [office-comment] Orientation problems with angles

• From: "Andreas J. Guelzow" <andreas.guelzow@concordia.ab.ca>
• To: <office-comment@lists.oasis-open.org>
• Date: Sat, 4 Aug 2012 23:29:53 -0600

```On Sat, 2012-08-04 at 21:07 -0600, Dennis E. Hamilton wrote:
> Are you not assuming the orientation of the +X and +Y axis directions
> and the placement of the origin from the perspective of the viewer in
> making that statement?

I don't see how the coordinate system has anything to do with
"clockwise" nor how the placement of the origin is involved in a
clockwise rotation. The clocks I know have no coordinate system nor an
origin (just a centre of rotation). The meaning of "clockwise" is
uniquely determined once we know on which side of the plane the viewer
is. And in the case of office documents this is always clear.

Andreas

>
> -----Original Message-----
> From: Andreas J. Guelzow [mailto:andreas.guelzow@concordia.ab.ca]
> Sent: Saturday, August 04, 2012 17:27
> To: office-comment@lists.oasis-open.org
> Subject: Re: [office-comment] Orientation problems with angles
>
> On Sat, 2012-08-04 at 15:04 -0600, Regina Henschel wrote:
> > Hi members,
> >
> > a lot of places, which use angles, are not exact enough about the
> > direction of the angle. The reason for this problem is, that the spec
> > does not define a coordinate system and therefor terms like "clockwise"
>
> If we are talking about angles in a plane document with respect to
> rotations, what is ambiguous about "clockwise"?
>
> > or "start at 12 o'clock" are ambiguous. Sometimes a direction is totally
> > missing or even a leg of the angle is missing. To get an angle with
> > directions you need an ordered pair of rays.
>
> A rotation in the plane is uniquely determined by its centre, the
> measure of the angle and whether angles are measured clockwise or
> counterclockwise.
>
>
> >
> > How to improve the situation?
> > (1) Do not define own elements or attributes, when well defined one
> > exists in SVG.
> > (2) Illustrate the definitions, for example as it is done in SVG for the
> > coordinate system
> > [http://www.w3.org/TR/SVG/coords.html#InitialCoordinateSystem]
> > (3) Be careful to define the legs of the angle as ordered pair of rays
> > for every angle.
>
> > (4) Deprecate an attribute, when it has often been implemented with
> > wrong direction, and define an unambiguous solution.
>
> If implementations have bugs, those bugs should be fixed rather than the
> standard changed.
>
> Andreas
>
>
> --
> Andreas J. Guelzow, PhD, FTICA
> Concordia University College of Alberta
>
>

--
Andreas J. Guelzow, PhD, FTICA
Concordia University College of Alberta
```

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