History
Some details to take care of:
- The first edition of ISO 10303-21:1994 had some bugs, which were corrected by a Technical Corrigendum. Therefore, it is recommended that users study the second edition instead (see below).
- The second edition ISO 10303-21:2002, including all the fixes and extensions for several data sections.
- Part 21 defined two conformance classes. They differ only in how to encode complex entity instances.
- Conformance class 1 is always used enforce the so-called internal mapping, which is more compact.
- Conformance class 2, which is not used in practice, always enforces the external mapping. In theory this would allow better AP interoperability, since a postprocessor may know how to handle some supertypes, but may not know the specified subtypes.
- The 1st edition of part 21 enforces the use of so-called SHORT NAMES, which are optional in the 2nd edition. In practice, however, SHORT NAMES are rarely used.
- The 2nd edition allows multiple data sections to be used. In practice, however, most implementations only use a single data section (1st edition encoding).
Read more about this topic: ISO 10303-21
Famous quotes containing the word history:
“What would we not give for some great poem to read now, which would be in harmony with the scenery,—for if men read aright, methinks they would never read anything but poems. No history nor philosophy can supply their place.”
—Henry David Thoreau (1817–1862)
“It is true that this man was nothing but an elemental force in motion, directed and rendered more effective by extreme cunning and by a relentless tactical clairvoyance .... Hitler was history in its purest form.”
—Albert Camus (1913–1960)
“The history of the Victorian Age will never be written: we know too much about it.”
—Lytton Strachey (1880–1932)