Extending an extension, or nested extensions?

[balazsdukai]

Is it allowed to use an extension in an extension? Or should it be allowed?

This not mentioned explicitly in the specs. Only in case case of the core CityJSON specs, but the wording is a bit vague I think.

• It is allowed to use multiple extensions in a core CityObject type (eg Bulding, Bridge etc).
• It is allowed to reuse parts of the core CityObjects in an extended CityObject.

But could we reuse parts of an extended CityObject in an extended CityObject?

For instance, we have an extension (A) that defines attributes of measurements with various units.
The second, domain extension for noise data (B) reuses some of the measurement-attributes from A.