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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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Once a script structure for a given context is desired, answering queries for a<br />

particular incident that can be mapped to the given script is possible.<br />

For instance, suppose we have the examination script of fig 8.17. We are now<br />

told a story as follows:<br />

“ Jim entered the examination hall <strong>and</strong> came out with a question paper .”<br />

Now, if we ask, “Did Jim appear at the examination?”<br />

We immediately answer “Yes”.<br />

A program that realizes a script can also answer such queries. One<br />

important issue that we do not discuss here is that the capacity of inheritance<br />

of the slots in a script. A script is a collection of slots. So, it also supports the<br />

capability of inheritance like a frame.<br />

8.11 Conclusions<br />

The chapter covered a wide range of structured models, including semantic<br />

nets, frames, Petri nets, scripts <strong>and</strong> conceptual dependency graphs (CDs).<br />

Semantic nets are useful for their application in monotonic, non-monotonic<br />

<strong>and</strong> defeasible reasoning. CDs are more powerful tools for knowledge<br />

representation, but have limited use in monotonic systems. Scripts are<br />

mainly useful to represent complex scenes, which by other means are too<br />

difficult to be realizable. The work of Schank <strong>and</strong> his group in building a<br />

Script Applier Mechanism (SAM) system at Yale University, in this regard,<br />

needs special mention. The above system reads a text <strong>and</strong> reasons with it to<br />

underst<strong>and</strong> stories.<br />

Among the recently developed structured models, Petri nets are the<br />

most popular for their parallel <strong>and</strong> distributed architecture. They can also<br />

h<strong>and</strong>le the inexactness of data <strong>and</strong> knowledge by fuzzy or stochastic tools.<br />

However, if someone wants to use binary logic only, then semantic nets <strong>and</strong><br />

their inheritance in the presence of defeasible reasoning should be adopted.<br />

There exists an ample scope of work on defeasible reasoning <strong>and</strong> its<br />

realization on different structured models. A unified model that can h<strong>and</strong>le all<br />

typical kinds of reasoning has yet to be developed.<br />

Exercises<br />

1. Represent each of the the following pieces of knowledge by a semantic<br />

net. (a) Loves (mary, john), (b) Loves (mary, john) ∧ Hates (john, mita),<br />

(c) Loves (mary, john) →Hates (mita, john).

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