DTV 1.3 RTF Avatar
  1. OMG Issue

DTV13 — 'overlaps' is symmetric not synonymous

  • Key: DTV13-67
  • Status: closed  
  • Source: Thematix Partners LLC ( Mr. Edward J. Barkmeyer)
  • Summary:

    In clause D.4, in the entry for 'part1 overlaps part2', we find:
    Synonymous Form: part2 overlaps part1
    Definition: There exists a part3 that is part of the part1 and the part3 is part of the part2.

    There are two problems here:
    1) 'part' is not a general concept, and the range of the roles part1 and part2 is not specified. The CLIF says they are both 'thing'. So the fact type should probably be 'thing1 overlaps thing2'. Similarly, we have no idea what a 'part3' might be. The definition should read: 'there exists a thing that is part of thing1 and is part of thing2'.

    2) part2 overlaps part1 is not a synonymous form of 'part1 overlaps part2'. It is the same form. The main entry defines the symbol 'overlaps' between two instances of type 'thing'. Since the placeholders do not appear in a use of 'overlaps', it makes no difference what their spelling is. What is intended here is in fact an "axiom of symmetry":
    Necessity: If a thing1 overlaps a thing2, then the thing2 overlaps the thing1.

    Similarly, in clause 8.2.1, in the entry for 'time interval1 overlaps time interval2', we find:
    Synonymous Form: time interval2 overlaps time interval1
    This is the same problem (s). 'time interval2 overlaps time interval1' is the same form as 'time interval1 overlaps time interval2' because the symbol and its context (the ranges of the roles) are the same. This should also be stated as an axiom:
    Necessity: If a time interval1 overlaps a time interval2, then the time interval2 overlaps the time interval1.

  • Reported: DTV 1.2 — Sat, 6 Jun 2015 00:09 GMT
  • Disposition: Resolved — DTV 1.3
  • Disposition Summary:

    Replace the synonymous forms for 'overlaps' with necessities.

    As described in the Issue, x1 overlaps x2 and x2 overlaps x1 are the same form. In clause 8.2.1 replace the synonymous form: time interval2 overlaps time interval1 with a Necessity: If time interval1 overlaps time interval2 then time interval2 overlaps time interval1. And similarly for part1 overlaps part2 in D.4.

  • Updated: Tue, 12 Jul 2016 14:45 GMT