UCM12 — Introduce name spaces to split declarations across several files

Although it is not explicitly specified in the standard, UCM modules cannot be
declared in several parts. Hence, a UCM module and all its submodules must be
gathered in a single file; such a file may be difficult to read if there are
many submodules.

It would be nice to introduce the notion of name space in UCM. A UCM name space
would be a specific kind of module that can contain any type of module. A UCM
name space could be declared several times (each declaration in a separate
file).

Example:
In file sys--components.xml

<namespace name="sys">
  <componentModule name="components">
  […]
  </componentModule>
</namespace>

In file sys--contracts.xml

<namespace name="sys">
  <contractModule name="contracts">
  […]
  </contractModule>
</namespace>

Currently, only the following declarations are allowed:

<applicationModule name="sys">
  <componentModule name="components">
  […]
  </componentModule>
  <contractModule name="contracts">
  […]
  </contractModule>
</applicationModule>

This would enable split a large UCM model in several files while keeping a
common naming scheme.

add the notion of namespace

Issue UCM12-1 is addressed by creating a new class named “Namespace” in the metamodel. This class derives from class “IModule”.
The meta-model and the XML representation (DTD and schema) are updated.