Costello, Roger L. wrote:
> Do you agree that this stylesheet document is not a declarative XML document?
>
I don't think the opposite of "declarative" is really "procedural". The
opposite of "procedural" is "functional". XSLT considered functional,
not procedural, because functions do not have side effects (variables'
values cannot be updated.)
The opposite of "declarative" is "algorithmic": declarative says what
you want, algorithmic says how you do it.
So I think XSLT is declarative when using the template and XPaths, but
algorithmic when using recursion. You can see that the use of
<xsl:when> rather than <xsl:if> betrays the concern to try to be as
declarative as possible.
There are implementation distinctions. The more declarative some program
is, the more that it can be parallelized and optimized and have
evaluation re-ordered. This is the same benefit that pure "functional"
languages have, but "declarative" is not the same as "functional" and
"algorithmic" is not the same as "procedural".
In your example, I think it is declarative, because there is just an
identity established, and there is nothing given about how it should be
implemented. The following two are algorithmic however:
(map 'sum xpath( "/purchases/merchandise/cost" ))
or
int cost[] = get-xpath( current-doc, "/purchases/merchandise/cost" );
int value = 0;
for-each (cost) {
value += cost;
}
In XSLT you cannot tell how a built-in function is implemented: just
invoking a function is declarative IMHO.
Cheers
Rick Jelliffe
