Three options are possible: 

1. Option 1 - xsd:documentation refers to element group
2. Option 2 - xsd:documentation refers to specific group element such as ABIEDocumentation
3. Option 3 - xsd:documentation refers to a single root element

Option 1

Option 1 is a mixture of XML Schema and CCTS annotation/documentation schema. The xsd:documentation refers to the specific element group such as doc:ABIE_Documentation, directly. Each element group must be selected in accordance with the defined artefact type at XML Schema level. The following figure shows the reference between xsd:documentation and the specific element groups.

Advantages:

• No interim level and redundancy
• Efficient representation of documentation as it required

Disadvantages:

• The reference between xsd:documentation and the specific element groups does not exactly follow the XML Schema conventions
• The selection of specific element groups requires additional tool support

Option 2 

In option 2 the xsd:documentation refers to a root element, which considers specific element group. Every CCTS specific artefact requires a root element, which must be spearately named such as ABIEDocumentation etc. The following figure shows the reference between xsd:documentation and the root elements.

Advantages:

• Follows XML Schema conventions
• Separates XML Schema and the documentation schema

Disadvantages:

• Has an (unnecessary) additional hierachical level, because of XML Schema restrictions
• The root element names considers redundant information such as "Documentation" and the acronym type.
• Needs tool support, anyway.

Option 3 

In option 2 the xsd:documentation refers to a single root element, which is named as CCTSDocumentation. The CCTSDocumentation has a choice of the documentation of the CCTS specific. Each specific documentation must be separately named such as ABIEDocumentation etc. The following figure shows the reference between xsd:documentation and the single root element.

Advantages:

• It is the preference of XML Schema, having a single root element within a schema

Disadvantages:

• Has two (unnecessary) additional hierachical levels, because of XML Schema restrictions + preferemce
• The two additional elements considers redundant information such as "CCTS Documentation", and acronym type + "Documentation".
• Needs tool support, anyway.