Annotate the data model with common elements

[mlagally]

Examples include:
Accuracy
Timestamps
Geolocation Information

These could be handled by annotations:
For accuracy we could allow SSN as an extension
Geolocation may also be handled by an extension
timestamps

[benfrancis]

I don't think I understand this issue, what exactly are you suggesting? I don't think we need to "allow" extensions as they are already allowed by default. Propose closing.