Re: [xmile] 1.5.2 Non-Apply-to-All Array

[Will Glass-Husain <wglass@forio.com>]

Bobby,

I prefer your syntax -- it's much clearer and concise.   If you are hand-editing models it reducing the likelihood of errors since there is less duplication.

This seems an important proposal to me, and feasible to include.

WILL

On Mon, Jun 2, 2014 at 8:28 AM, Bobby Powers <bobbypowers@gmail.com> wrote:

Hello,

I think this section needs work, I would not like to see the current specification approved with two distinct ways to create arrays.

To review, arrays with a singe equation for all dimensions (apply to all) is created like this:

<aux name="distance">
  <dimensions>
    <dim name="X"/>
    <dim name="Y"/>
  </dimensions>
  <eqn>SQRT(X^2 + Y^2)</eqn>
  <units>kilometers</units>
</aux>

And one with different equations for different dimensions is created like this:

<array name="not_apply_to_all">
  <dimensions>
    <dim name="X"/>
    <dim name="X"/>
  </dimensions>
  <aux subscript="1,1">
    <eqn>TIME</eqn>
  </aux>
  <aux subscript="1,2">
    <eqn>2*TIME</eqn>
  </aux>
  <aux subscript="2,1">
    <eqn>TIME^2</eqn>
  </aux>
  <aux subscript="2,2">
    <eqn>2*TIME^2</eqn>
  </aux>
  <units>Euros</units>
</array>

Having a top-level array tag is unintuitive to me.  Apply-to-all gets it right - the most important piece of information about a variable is its type <aux>, not that it is an array.  Changing the outermost tag from <aux> to <array> when changing the variable from an apply-to-all array to a non-apply-to-all array doesn't make sense from a spec standpoint - you don't have multiple variables, you have multiple equations for the same variable.

I suggest changing this to simply allowing the subscript attribute on the <eqn> tag:

<aux name="not_apply_to_all">
  <dimensions>
    <dim name="X"/>
    <dim name="Y"/>
  </dimensions>
  <eqn subscript="1,1">TIME</eqn>

  <eqn subscript="1,2">2*TIME</eqn>
  <eqn subscript="2,1">TIME^2</eqn>
  <eqn subscript="2,2">2*TIME^2</eqn>

  <units>Euros</units>
</aux>

A sidenote - the above example from the spec is not dimensionally consistent - it has a variable with equation TIME and units Euros.  Do we want/need to edit the spec for dimensional consistency in examples?

yours,

Bobby

--

William Glass-Husain   /forio  |  +1 (415) 440 7500 x89  |  forio.com