On 5 Nov, 11:20, Sven <s...@ast.dfs.de> wrote:
> What is the intention of xs:all? Is it just the same like xs:sequence
> with having no strict order? But in xs:all all elements have to be
> present exactly one time, right? There is no possibility to define
> optional or multiple elements?!
>

xs:all is similar to xs:sequence, but, as you say, does not impose a
strict order.  Elements from an xs:all in an XML instance can occur 0
or 1 times, but _not_ 2 or more.  Unlike like xs:sequence, xs:all does
not allow anonymous compositors, can't be used as an anonymous
compositor, and can't extend from a base or be extended.

> By the way, why is s sequence the main collection type? I can see no
> reason for a strict order of the child elements anyway.

The restrictions on xs:all were imposed because at the time it was
thought that the impact on a finite state machine implementing
validation would suffer combinatorial explosion type problems.  I
imagine that xs:sequence is ordered for similar reasons.  (Note that
it's now considered that there are better ways to validate xs:all than
implementing a finite state machine and future versions of schema are
likely to allow more relaxed forms of xs:all.)

HTH,

Pete Cordell
Codalogic
Visit http://www.codalogic.com/lmx/
for XML Schema to C++ data binding