ISO 10303-21 - History

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 is most interesting and valuable in it, however, is not the materials for the history of Pontiac, or Braddock, or the Northwest, which it furnishes; not the annals of the country, but the natural facts, or perennials, which are ever without date. When out of history the truth shall be extracted, it will have shed its dates like withered leaves.”
    —Henry David Thoreau (1817–1862)

    “One classic American landscape haunts all of American literature. It is a picture of Eden, perceived at the instant of history when corruption has just begun to set in. The serpent has shown his scaly head in the undergrowth. The apple gleams on the tree. The old drama of the Fall is ready to start all over again.”
    —Jonathan Raban (b. 1942)

    “What we call National-Socialism is the poisonous perversion of ideas which have a long history in German intellectual life.”
    —Thomas Mann (1875–1955)