Table of contents

Appendices

2.5 Names and Symbol Spaces

As discussed in [XML Schema Abstract Data Model], most schema components (may) have component name. If all such names were assigned from the same "pool", then it would be impossible to have, for example, a simple type definition and an element declaration both with the name "title" in a given target namespace.

Therefore this specification introduces the term symbol space to denote a collection of names, each of which is unique with respect to the others. A symbol space is similar to the non-normative concept of namespace partition introduced in [ref-xml-namespaces]. There is a single distinct symbol space within a given target namespace for each kind of definition and declaration component identified in [XML Schema Abstract Data Model], except that within a target namespace, simple type definitions and complex type definitions share a symbol space. Within a given symbol space, names are unique, but the same name may appear in more than one symbol space without conflict. For example, the same name can appear in both a type definition and an element declaration, without conflict or necessary relation between the two.

Locally scoped attribute and element declarations are special with regard to symbol spaces. Every complex type definition defines its own local attribute and element declaration symbol spaces, where these symbol spaces are distinct from each other and from any of the other symbol spaces. So, for example, two complex type definitions having the same target namespace can contain a local attribute declaration for the unqualified name "priority", or contain a local element declaration for the name "address", without conflict or necessary relation between the two.