Validator should check:
1. resource references in pages: xhtml, jsp, jspxand etc.
2. resource names defined in current project or related projects
3. resource names defined in jars

It should perform verification for JSF2 resources as it is defined in spec's "2.6.1.3 Resource Identifiers" chapter: "<resourceIdentifier> consists of several segments, specified as follows.
[localePrefix/][libraryName/][libraryVersion/]resourceName[/resourceVersion]
The run-time must enforce the following rules to consider a <resourceIdentifier>s valid. A <resourceIdentifier> that does not follow these rules must not be considered valid and must be ignored silently.

• Every character in a resource identifier must be a valid character suitable for use in a string passed to the constructor of java.io.File that takes a single String argument.
• Segments in square brackets [] are optional.
• The segments must appear in the order shown above.
• If libraryVersion is present, it must be preceded by libraryName.
• If libraryVersion is present, any leaf files under libraryName must be ignored.
• If resourceVersion is present, it must be preceded by resourceName.
• There must be a '/' between adjacent segments in a <resourceIdentifier>
• If libraryVersion or resourceVersion are present, both must be a '' separated list of integers, neither starting nor ending with ''
• If resourceVersion is present, it must be a version number in the same format as libraryVersion. An optional "file extension" may be used with the resourceVersion. If "file extension" is used, a "." character, followed by a "file extension" must be appended to the version number. See the following table for an example."