Submitter: Henderson

Addressed to: JTC1/SC 24/WG 6 Rapporteur Group on ISO/IEC 8632, CGM

WG secretariat: NNI

Date Circulated by WG secretariat: 1 July 1995

Deadline on response from editor: : 1 October 1995

Defect Report concerning IS 8632:1992 Computer Graphics: Metafile for the storage and transfer of picture description information (CGM) Part 1, Functional

specification.

Qualifier (e.g. error, omission, clarification required): Correction

References in document (e.g. page, clause, figure and/or table numbers):

Geometric Pattern Definition, clause 5.4.19 (p.153) and clause 6 (p.228).

Nature of defect (complete, concise explanation of the perceived problem):

The second paragraph of 5.4.19 states, "The segment identifier identifies an existing, defined segment whose primitives are used to define the geometric pattern." Clause 6 states the default value of the geometric pattern is "1, 1, default VDC Extent" (note that the second "1" is omitted, but this is the subject of defect report number 1/002).

The problem is that there is no default segment number 1.

In practice, this would not present a problem as long as geometric pattern index 1 were not referenced. However, it should be possible for a generator to explicitly write all defaults into a metafile and still have a valid metafile. In this case, and this case alone amongst those elements which have defined defaults, such generator action would apparently create an invalid metafile by violating the constraint of the 2nd paragraph of 5.4.19.

For the Geometric Pattern Definition element, a default really does not make sense. The best solution would be to change clause 6 to indicate "no default defined". This correction should not cause any problems with implementations, as the concept of default with Geometric Pattern Definition is not at all useful (and therefore is almost certainly

unused) .

Change the default for GEOMETRIC PATTERN DEFINITION in clause 6 to "n/a".

Amend the standard as proposed above.