Property Table aggregate similar properties into Subjects. For all possible Property there is another Column. In there Clustering of all similar subjects is not a trivial task to do and is most time performed by hand. If there are multivalued Properties it becomes difficult as it results in several rows with the same item or Entity which makes the complexity even worse.
Combining all (or some) Properties of similar Subjects in n-ary Tables
Use ID based encoding for efficiency.
Pros
Fewer joins
If the data is structured, we have a relational DB
Cons
Potentially a lot of NULLS
Clustering is not trivial
Multi-value Properties are complicated
