Some properties are for internal use only, e.g. for collaboratively computed properties, the analysis might need an internal property to keep a dependency to the TAC. These properties are only used to keep the framework mechanisms working and should never be used/accessed by any client (or other analysis).
A simple solution would be to throw an exception, whenever the property store is queried with a property key of an internal property. However, there might be more elegant solutions. Maybe some framework changes would remove the need for these properties. Maybe the properties should be created by the framework internally.
If such properties are needed, a generic property, that can be used by any analysis, would be an enhancement.