>
> So, to me, the decisions of the W3C working group seems random, and rather
> based on a two years old
> kind of a tantrum “I WANT TO BE DIFFERETENT JUST BECAUSE…..I WANT IT."
>
>
> ……...rather then justified by any technical reasons.
>
No, all the arguments were all technical. For example:
* generalizing maps to allow any atomic type as the key, rather than only a
string, was because of specific use cases that required this (remember that the
first proposal to add maps to XDM came from XSLT streaming work, not from
JSONiq)
* the decision to use “map{…}” rather than “{…}” was to some extent subjective,
but was motivated by technical arguments such as the ability to produce good
error messages, retaining options for future extensions to the grammar, etc.
Expressions beginning with “{“ are particularly problematic because “{“ is used
to delimit embedded expressions in element content, and “{{“ is used to escape
“{“ as an ordinary character; they are also very obscure when used as the body
of a function (declare function f {{1:2}}). Before making this decision, we
looked at how many other popular languages solve this problem.
* the decision to allow any sequence to act as a member of an array enabled
things like the fn:apply() function, whose second argument is an array of
arbitrary sequences; it also enabled JSON null to be represented by an empty
sequence, which avoided the need for pervasive changes to the language to
define how every function and operator should handle a JSON null. Reducing the
number of concepts by one is a definite plus.
Getting agreement on all these points was a very lengthy process with much
heated argument. Although the decisions made were not always the ones I
personally advocated, I think the final language works well. If there’s one
aspect I’m still a little unhappy about, it’s the fact that an array behaves
like a single item, so for example
let $A := [1,2,3]
return $A[1]
returns [1,2,3]
But that’s there because we tried very hard to find a way to avoid this
surprise, and failed: the sequence=item model in XDM is just too deeply
embedded.
Michael Kay
Saxonica
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