targetnamespace - what is it?!?!

[kevin bailey]

hi there,

i'm reading up on schema - but am probably missing something obvious RE
targetnamespace

i know there can only be one...

is it that the elements which are defined in the schema which have no
prefix are somehow now part of the namespace - would it need to upload the
definitions?

it says
targetnamespace - 'namespace to which all global schema components belong'

but what the point of that - there is already a default namespace
xmlns="http://....."

and anyway - what is a 'global schema component'?

thanks for ANY help?

kev bailey

 

[kevin bailey]

targetNamespace = "THIS" says that "this schema describes elements that
belong to THIS namespace". So it sorts of defines a namespace. Then it can
get more complicated of course, for instance several schemas can define
parts of the same namespace. Let's say one schema describes a "car"
element in namespace "asdflj234lk234/namespaces/vehicels", and another
schema defines a "truck" element in the same namespace.

The xmlns= "THIS" says that all elements and attributes that are NOT
prefixed belong to THIS namespace.

A global comonent (element) is defined at the "top level" of a schema
document. The "car" element is the at the top level, and then I might
define that it has wheels elements within the car element. The wheels
elements are not global then, they are local.
Global elements can be used several times, in different places and levels
(not top level again though).

a bit more advanced:
However, I COULD define a wheel element on the toplevel as well, and thus
make it global. They would not be WITHIN the car element then. I could
then say that a car has wheels by defining an element within the car that
_references_ the global wheel elements with the ref attribute.
If and instance was checked against this schema, it would conform if
1) it had a car element with wheels in it
2) it had a wheel only

This is because there is no in XSDL way to define a root element. All
global elements CAN be the root! (Personally I think that sucks

thanks loads for the reply - after reading it a couple of times it has
certainly helped to clear some of the mist!!

am i right in thinking that the targetnamespace is useful when a schema is
made up from several xsd files all linked together via
import/include/redefine - it means then that another part of the schema can
reference an element by using its namespace?

kev bailey