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*Subject*: **Re: Repeat M-N times**

*From*:**Josh Lubell <lubell@cme.nist.gov>***To*: TREX Discussion List <trex@lists.oasis-open.org>*Date*: Wed, 21 Feb 2001 15:13:15 -0500

From: "James Clark" <jjc@jclark.com> > Thank you. This was just the sort of example I was looking for. Do you > have any feeling for which of the following are most common: > > > > - repeat N or more times, where N > 1 Sets with N=2 and ordered lists with N=2 or N=3, while not very common in STEP models, are not not uncommon as parameters for curve fits, such as boundary representation data. That is, there are very few conceptual objects with these constraints, but those few are used a great deal in the data for certain applications, particularly mathematical representations. E.g. in one particular STEP model there are exactly three such "elements", but they typically occur hundreds or thousands of times in data files. > > > - repeat between 0 and N times, where N > 1 > > > - repeat between 1 and N times, where N > 1 Sets of repetitions between 1 and 2 times, 1 and 3 times, 0 and 2 times, and 0 and 3 times are very rare, but they do exist. Other sets and ordered lists with upper-bounds are almost always artifacts of the intent to map the model to an array in Java or C. > > > - repeat exactly N times, where N > 1 This is the standard representation of an array in STEP, including a vector or a matrix, and it is far and away the most common of these cases. One also sees unordered tuples in combinatorics and other applications. > > > - repeat between M and N times, where 1 < M < N I don't know of a valid example of this. As I said above, there are models in which the upper-bound is an artifact of the intent to map to a C (or Fortran or COBOL) array. I would be careful to distinguish "the data model" from "the business rule". There are a number of conceptual aggregates in STEP for which the data model wants to be a set of zero or more items or an ordered list of one or more items to allow general use of the model, while the rules for the use of the model within a given organization or among several trading partners will place specific minima (and sometimes maxima) on the sizes of those aggregates. Joshua Lubell, NIST 100 Bureau Drive, Stop 8263 Gaithersburg MD 20899-8263 USA (301) 975-3563 lubell@nist.gov

**References**:**Repeat M-N times***From:*James Clark <jjc@jclark.com>

**Re: Repeat M-N times***From:*Josh Lubell <lubell@cme.nist.gov>

**Re: Repeat M-N times***From:*James Clark <jjc@jclark.com>

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