Logic and set theory ; symbols and concepts 逻辑和集论.符号和概念
Versa also provides facilities - such as full boolean logic and set operations , transitive operations , aggregates , substring matching , and other core data type manipulation - that are lacking in many other rdf query systems Rdf模型是图形结构,该结构可以非常简单也可以令人难以置信的复杂。事实上,极端情况下, semantic web的设想是要创建至少同当前web一样大的rdf模型。