Which Is the Tallest Building in Europe? Representing and Reasoning About Knowledge

The need for representing knowledge is ubiquitous in applications; for example, Google needs to represent knowledge about the location and height of building in order to answer questions such as “which is the tallest building in Europe”. Google uses a graph to represent such knowledge, and so-called knowledge graphs are becoming increasingly popular as a knowledge representation formalism. Adding some form of rules greatly increases the power and utility of knowledge graphs, but can also lead to theoretical and/or practical tractability problems. In this papers we will briefly survey the relevant issues and possible solutions, and show that rule enhanced knowledge graphs are extremely powerful, can be given a formal logic-based semantics, and are highly scalable in practice.