**Problem**
Sometimes, it is necessary to know details //about// a statement group. Unfortunately, Wikibase does not provide a way to do this.
**Example**
I am certain that the list of [[ https://www.wikidata.org/wiki/Q30224326 | themed areas ]] in the [[ https://www.wikidata.org/wiki/Property:P527 | has part ]] property of [[ https://www.wikidata.org/w/index.php?title=Q1880820&oldid=997438017 | Universal Studios Florida ]] is **complete** (in the current sense, not the historical one as themed areas like "Amity Island" are missing, but no longer exist). I am also confident that the list of [[ https://www.wikidata.org/wiki/Q30224326 | themed areas ]] in the [[ https://www.wikidata.org/wiki/Property:P527 | has part ]] property of [[ https://www.wikidata.org/w/index.php?title=Q1052042&oldid=1043079136 | Epcot ]] is **incomplete** (but //can// be completed). I am aware of this, but there is no way to express this in Wikidata to other users and machines. Therefore, it's impossible to be able to answer: How many [[ https://www.wikidata.org/wiki/Q30224326 | themed areas ]] does each [[ https://www.wikidata.org/wiki/Q2416723 | theme park ]] have? You might //think// you have the answer based on what is provided (you may assume the property is complete), and not realize that you don't. For these two results you would have `8` and... `>1` would be the proper answer. If you were to assume that it is always incomplete, then you would never be able to answer this question, even if all of the [[ https://www.wikidata.org/wiki/Q2416723 | theme parks ]] had a complete set, there would be no way to know they were complete.
**Proposed Solution**
Perhaps when statement groups need properties, an intermediate object (like [[ http://blog.schema.org/2014/06/introducing-role.html | schema.org's Role ]]) could be added so those properties can be added to the statement group itself.
**Work Around**
# A common work around on Wikidata is to create another property that has the //count// of items. For instance [[ https://www.wikidata.org/wiki/Property:P2437 | number of seasons ]] and [[ https://www.wikidata.org/wiki/Property:P4908 | season ]], the former informing the completeness of the latter.
# Another common workaround is to create [[ https://www.wikidata.org/wiki/Q12139612 | list ]] items like [[ https://www.wikidata.org/wiki/Q52105174 | reasons for deprecation ]] that could have an [[ https://www.wikidata.org/wiki/Property:P2429 | expected completeness ]] property