Metadata Recommendations (Section 14)

9.4 Metadata
This is a better design than the last version. But it still seems unsatisfactory when it comes to how it will be applied to Haystack tags. In Haystack the vast majority of tags are marker tags which the proposed oBIX spec requires those tags to be sub-objects. But in reality marker tags are much closer to oBIX contracts. I think it would be cleaner to define marker tags in the "is" attribute using their tagspace as their prefix. Consider:

// proposed version
<obj displayName="Discharge Temp Sensor">
<obj ts="h" name="discharge"/>
<obj ts="h" name="temp"/>
<obj ts="h" name="air"/>
<obj ts="h" name="sensor"/>
<obj ts="h" name="point"/>
</obj>

// versus simpler design
<obj displayName="Discharge Temp Sensor"
is="h:discharge h:temp h:air h:sensor h:point">
</obj>