Local namespace

[John Snelson]

Martin Probst wrote:
> Indeed, you may not define functions or variables in modules that
> don't have the same namespace URI as the module:
> 
> "The name of every variable and function declared in a library module
> must have a namespace URI that is the same as the target namespace of
> the module; otherwise a static error is raised [err:XQST0048]."
> 
> Why that must be, I have never understood. It doesn't save the user
> from hard-to-find typo errors errors as you'd always declare the
> namespace prefix while declaring the module namespace, and then use
> that prefix. And it (IMHO) actively acts against modularization, as
> local variables or functions are highly desirable. In X-Hive / xDB, we
> have never followed that spec rule and allowed local
> functions/variables in modules, those are simply not exported to
> importing modules.

XQuery 1.1 is introducing the "private" function modifier, which will
allow the definition of functions that aren't exported from a module.

> I have also never really understood why it must be possible to have
> one module with one target namespace split over multiple files; I
> think Java has shown that the forced one-to-one relationship between
> conceptual name (class) and file (.java) is a good thing.

1) Modules aren't classes, they are more like library APIs.

2) Java's rules are by no means universally considered a good thing. In
particular it might be beneficial to split up a 5000 line Java class
into multiple files, or to group together implementations of the same
method from multiple implementations of a class.

3) Actually the XQuery spec doesn't say anything about whether a module
namespace can be split across multiple module files - that's left
implementation defined.

John

-- 
John Snelson, Oracle Corporation            http://snelson.org.uk/john
Berkeley DB XML:            http://oracle.com/database/berkeley-db/xml
XQilla:                                  http://xqilla.sourceforge.net