L20n/Projects/Type Annotation File Format
Current status is "in thought". We might be able to make html5 with semantics do the trick.
Tools would like to help localizers get internal and external properties right. Which of those are known is determined by type annotations in the source file format. The definition of those types will depend on the target language for internal properties, and on the application code when it comes down to external properties.
A strict type system. In the end, the localizer is right, not the tool.
These are the bugs of interest: