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