Re: Highly Declarative Designs

Roger--

It seems to me you need to amplify a bit.  For example:

a.  You seem to be making a sharp distinction between "navigating markup" and "processing data".   But why isn't navigating markup (or searching through any other kind of data structure) "processing data"?   Do you have some specific kind of "processing" in mind when you make this distinction?

b.  Further to (a), in your discussion you talk about "processing" regular expressions as opposed to "navigating" markup.  While there's certainly a distinction here, aren't regular expressions "declarative", and aren't you also "processing" the markup (different syntax, but still processing)?

c.  After one extremely simple example, you conclude with a recommendation "Wherever possible, use highly declarative designs".  I suppose the "wherever possible" gives you some wiggle room, but still it seems you're making this recommendation with little or no consideration of what the problem is, or what the tradeoffs might be.   Do you really think, for example, that navigating an extremely large file of markup is *always* better, considering time and space tradeoffs, than doing a simple computation?  Or that navigating an extremely large file of markup is always better than "processing" (to use your term) some other data structure that might be better adapted to the problem?  Suppose, for example, the question you wanted answered had to do with the structure of the family name (say, for a start, whether spaces were allowed)?  Can you give us the markup that conveys all the information conveyed by the regular expression (without using the regular expression) and show that navigating that markup is preferable to "processing" the regular expression?  Or, going at this another way, under what circumstances would it not be *possible* to use a highly declarative design?

It's one thing to point out that one might want to consider "highly declarative design" as one tool in a "designer's toolbox".  But it seems to me you've gone well beyond that.

--Frank

On Feb 5, 2011, at 9:17 AM, Costello, Roger L. wrote:

> Hi Folks,
>
> Issue: What are the characteristics of a highly declarative design?
>
> I propose this as a characteristic:
>
>    If you can ask a question and get the answer by
>    exclusively navigating markup, without any processing
>    of data, then you have a highly declarative design.
>
> More ... http://www.xfront.com/Highly-Declarative-Designs.pdf
>
> Comments welcome.
>
> /Roger
>
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