DDSXML — DDS System Block Set lacks Schema File and Example

The DDS System Building Block defined in sub clause 8.1 lacks a properly documented schema file and an example XML file that may be reused by other specifications (e.g., DDS-XRCE).

The RFC included a schema file (dds-xml_system_example.xsd) and an XML file (dds-xml_system_example.xml). However, these files were considered non-normative and were not linked to the specification document or the DDS System Building Block in any way.

This FTF should:

• move "dds-xml_system_example.xsd" to a pair of schema files following the chameleon schema patter (i.e., one without namespace and one with the standard namespace as modified by DDSXML-2).
• update "dds-xml_system_example.xml" to reference the file with a namespace.

Moreover, we should simplify the definition of the DDS top level element to be a choice of minOccurs="0" and maxOccurs="unbounded", which produces the same complexType with a more compact and correct syntax.

Finally, we should update clause 8.1 to link the building block to the corresponding schema files.

Create proper schema and example files for DDS Building Block Set

This resolution applies the following changes:
1. It creates proper schema and example files for the DDS Building Block Set defined in clause 8.1.
2. It transforms the DDS top-level type definition into a simple choice.
3. It adds a short paragraph at the end of clause 8.1 to reference those documents.