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:

    “No event in American history is more misunderstood than the Vietnam War. It was misreported then, and it is misremembered now.”
    —Richard M. Nixon (b. 1913)

    “All history attests that man has subjected woman to his will, used her as a means to promote his selfish gratification, to minister to his sensual pleasures, to be instrumental in promoting his comfort; but never has he desired to elevate her to that rank she was created to fill. He has done all he could to debase and enslave her mind; and now he looks triumphantly on the ruin he has wrought, and say, the being he has thus deeply injured is his inferior.”
    —Sarah M. Grimke (1792–1873)

    “The disadvantage of men not knowing the past is that they do not know the present. History is a hill or high point of vantage, from which alone men see the town in which they live or the age in which they are living.”
    —Gilbert Keith Chesterton (1874–1936)