Re: [xml-dev] Make implicit structures explicit

[Frank Manola <fmanola@acm.org>]

I think designing data structures without any consideration of what they are going to be used for isn't really "design" at all.


On Apr 8, 2014, at 4:09 PM, "Costello, Roger L." <costello@mitre.org> wrote:

> Hi Folks,
> 
> Suppose that you document the steps to be taken by an aircraft in its landing procedure:
> 
> 1. Contact control tower
> 
> 2. Enter glide slope
> 
> 3. Correct for wind conditions
> 
> Suppose those things must be followed in the sequence listed.
> 
> The XML could be designed like this:
> 
> <aircraft-approach-procedure>
>    <transition>Contact control tower</transition>
>    <transition>Enter glide slope</transition>
>    <transition>Correct for wind conditions</transition>
> </aircraft-approach-procedure>
> 
> That design relies (implicitly) on the order of the <transition> elements for denoting the sequence of steps to be taken. 
> 
> An alternative design is to (explicitly) specify the order. Here is one way to accomplish this:
> 
> <aircraft-approach-procedure>
>    <transition step="2">Enter glide slope</transition>
>    <transition step="3">Correct for wind conditions</transition>
>    <transition step="1">Contact control tower</transition>
> </aircraft-approach-procedure>
> 
> Note that in this design it is not necessary to list the <transition> elements in a particular order since @step explicitly indicates the order.
> 
> I vote for the latter as best practice. I invoke this principle as my justification: 
> 
> 	Make implicit structures explicit.
> 
> What do you think?
> 
> /Roger
>