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  1. OMG Issue

SYSML14 — SysML ISO-80000-1 libraries need update per 18269, 18435 and 18681

  • Key: SYSML14-34
  • Legacy Issue Number: 18707
  • Status: closed  
  • Source: NASA ( Dr. Nicolas F. Rouquette)
  • Summary:

    The ISO-80000-1 libraries need to be updated according to the resolutions of issues 18269, 18435 and 18681 in SysML 1.4 ballots 4 and 5.

  • Reported: SysML 1.3 — Sat, 11 May 2013 04:00 GMT
  • Disposition: Resolved — SysML 1.4
  • Disposition Summary:

    Prior to resolving 18269, there was a duplication of Unit and QuantityKind in SysML
    1.3 that had a corresponding duplication of non-normative libraries for a subset of
    ISO 80000-1:
    As explained in the discussion of 18269, the duplication of Unit and QuantityKind
    makes completing these libraries expensive due to the combinations implied in ISO-
    80000-1: Within the International System of Units alone, there are 20 decimal
    prefixes and 8 binary prefixes that can each apply to a Unit. ISO 80000 has 14 parts;
    part 1 defines 45 units (7 base units, 18 in Table 2, 4 in Table 3, 10 in Table 5 and 6
    in Table 6). Thus, a complete library of all legitimate pairs of Unit/QuantityKind in
    scope of ISO-80000-1 involves 45 * 28 = 1,260 pairs of prefixed units and quantity
    Following the resolution of 18269, the two ISO 80000-1 libraries from SysML 1.3 are
    merged into a single ISO 80000 library based on the non-normative QUDV model;
    that is, definitions of ISO 80000 units and quantity kinds are modeled as M1-level
    InstanceSpecifications classified by a kind of QUDV::Unit and QUDV::QuantityKind
    The name of the library is changed from ISO 80000-1 to just ISO 80000 to reflect the
    fact that the tables from which the SysML 1.2 and 1.3 ISO 80000-1 libraries came
    from are in fact summaries of units and quantities defined across several ISO 80000
    parts. For example, Table 1 in ISO 80000-1 shows the 7 base units and base
    quantities of the SI and ISQ respectively. These units and quantities come from ISO
    80000 parts 3,4,5,6,7 and 9. Annex D.4 previously showed diagrams for the ISO-80000-1-SysML library. D.4 is
    updated to show the library of units, prefixes and quantities referenced in ISO-80000-
    1 Tables 1 through 5 and from parts of Table 2 from the SI Brochure, which is not
    included in ISO 80000-1, but the contents of which was included in previous versions
    of SysML. Altogether, previous versions of SysML included definitions of units and
    quantities traceable to a small subset of ISO 80000 parts: 3,4,5,6,7,9 and 10. For
    SysML 1.4, the coverage is expanded to include all of the normative definitions of
    parts 3,4,5,6. The coverage of parts 7,9,10 remains the same. This resolution also
    includes the definition of units for bit, byte and octet and related quantities and binary
    prefixes from ISO 80000-13.
    This resolution addresses a problem reported by Hans-Peter de Koning about the
    typing of Linear and AffineConversionUnit factors and offset which were previously
    typed by Rational but should be typed by Number. This problem affects the precise
    definition of the degree as a unit of plane angle, which is not representable as a
    Rational (1 degree = Pi/180 radian).
    This resolution depends on the resolution of 18692 and 18724 in ballot 6; however,
    this resolution adds a capability for distinguishing derived units whose factors are
    reduced (e.g., joule) or not (e.g., kelvin joule per kelvin). Mathematically, a nonreduced
    derived unit is equivalent to a reduced derived unit (e.g., joule = kelvin joule
    per kelvin). This is used rarely (there are 152 derived units in total; 140 are reduced;
    only 12 are non-reduced). For the few cases where it’s been used, the justification
    stems from two general principles:

    • Ensure that all the QUDV-based derived units and quantities are
      mathematically derived in the same way as the derivations shown in their
      corresponding ISO 80000 definitions.
    • Ensure that the dependencies among the QUDV-based models of ISO 80000
      parts reflect the normative dependencies from the corresponding ISO 80000
      The only exception to the dependency principle stems from the dual definition of a
      unit, watt per square metre, in two ISO 80000 parts (5 and 6) that have no normative
      dependency to one another (parts 5 and 6 normatively depend on ISO 80000 parts 3
      and 4). The QUDV-based model has part 6 depend on part 5.
      In SysML 1.3, Figure D.7 showed the definition of a unit named ‘catalytic activity’ for
      a quantity kind named ‘katal’. Even though this appears in ISO 80000-1, Table 3,
      there is no indexed definition of this unit or quantity kind in any ISO 80000 part. Since
      all the units and quantity kind definitions in SysML 1.4 have an indexed definition in
      some part of ISO 80000, SysML 1.4 does not include ‘catalytic activity’ nor ‘katal’.
      Note about the tables of units and quantity kinds (Figure tables D8 and D11 through
      D23): The complete details pertaining to the QUDV-based definition of each unit and each
      quantity kind are available in the machine-readable file for the ISO 80000 library. The
      symbols for these units and quantity kinds have been reproduced in Presentation
      MathML on a best-effort basis according to the ISO 80000 documents.
  • Updated: Fri, 6 Mar 2015 20:58 GMT