The manifest has an XML schema definition file. It is a part of the Titanium Website project in VS. The way that XSD's work is that they are by definition a published standard, requiring a URL. The URL for the current manifest is: http://wiki.titaniumcms.com/manifest.xsd. So if you need to modify the schema for whatever reason, you then need to update published file. If there is something so dramaitc as to require a version change, there is a version reference in the Manifest tag in the schema.
No matter the desired change, please ensure that it
1. All file location tags should be called <Path>
2. All assembly type name tags should be called <Type>
3. All elements should be in a pluralized structure - such as <Types><Type></Type></Types>
4. We need to use the same casing for all XML tags. I would like this to be normal camel casing. example: <PageTypeViews>