(26th-June-2020)
• The first part of this chapter considers a way to build flexible representations using the tools of logic. These flexible representations are the basis of modern ontologies.
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1. Choosing Individuals and Relations
2. Graphical Representations
3. Terse Language for Triples
4. Primitive Versus Derived Relations
• Given a logical representation language, such as the one developed in the previous chapter, and a world to reason about, the people designing knowledge bases have to choose what, in the world, to refer to. That is, they have to choose what individuals and relations there are. It may seem that they can just refer to the individuals and relations that exist in the world. However, the world does not determine what individuals there are. How the world is divided into individuals is invented by whomever is modeling the world. The modeler divides up the world up into things so that the agent can refer to parts of the world that make sense for the task at hand.
• For example, it may seem as though "red" is a reasonable property to ascribe to things in the world. You may do this because you want to tell the delivery robot to go and get the red parcel. In the world, there are surfaces absorbing some frequencies and reflecting other frequencies of light. Some user may have decided that, for some application, some particular set of reflectance properties should be called "red." Some other modeler of the domain might decide on another mapping of the spectrum and use the terms pink, scarlet, ruby, and crimson, and yet another modeler may divide the spectrum into regions that do not correspond to words in any language but are those regions most useful to distinguish different categories of individuals.
• Just as modelers choose what individuals to represent, they also choose what relations to use. There are, however, some guiding principles that are useful for choosing relations and individuals. These will be demonstrated through a sequence of examples.
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