UNIT-II-2 MARKS KNOWLEDGE REPRESENTATION 1. What are the two levels of knowledge representation? There are two levels of knowledge representation they are *Knowledge level: The knowledge levels at which facts are described (including each agent’s behavior and current goals). *Symbol level: the symbol level at which representation of objects at the knowledge level are defined in terms of symbol that can be manipulated by programs. 2. Draw the block diagram mappings between Facts and representation: Reasoning programs Internal representations

Facts English understanding

English representations

3. Draw the block diagram of representation of facts: Desired real reasoning Initial facts

*

Final facts

Forward representation

backward representation

Mapping

Mapping

Internal representation of initial states

Internal representation of initial facts Operation of program

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4. What are all the properties of good system which in-terms of representation of knowledge? *Representational Adequacy *Inferential Adequacy *Inferential Efficiency *Acquistional Efficiency 5. Define the issues in knowledge representation * To detect attributes *Relationship among attributes *Knowledge representation in level *Representation of objects *Large amount of knowledge stored in database 6. What are the two important attributes? The two important attributes are *instance *is a These two attributes important because they support inheritance. 7. What are the properties of relationship among attributes? *Inverses *Existence in an is a hierarchy *Techniques for reasoning about values *Single-valued attributes 8. What are Logical agents? Logical agents apply inference to a knowledge base to derive new information and make decisions. 9. Define a Sentence? Each individual representation of facts is called a sentence. The sentences are expressed in a language called as knowledge representation language. 2

10. Define a knowledge Base. Knowledge base is the central component of knowledge base agent and it is described as a set of representations of facts about the world. 11. Define Syntax? Syntax is the arrangement of words. Syntax of knowledge describes the possible configurations that can constitute sentences. Syntax of the language describes how to make sentences. 12. Define Semantics The semantics of the language defines the truth of each sentence with respect to each possible world. With this semantics, when a particular configuration exists within an agent, the agent believes the corresponding sentence. 13. Define an inference procedure An inference procedure reports whether or not a sentence  is entailed by knowledge base provided a knowledge base and a sentence . An inference procedure ‘i’ can be described by the sentences that it can derive. If i can derive  from knowledge base, we can write.KB  Alpha is derived from KB or i derives alpha from KB 14. Define Logic Logic is one which consist of i. A formal system for describing states of affairs, consisting of a) Syntax b)Semantics. ii. Proof Theory – a set of rules for deducing the entailment of a set sentences. 15. What is entailment? The relation between sentences is called entailment. The formal definition of entailment is this: if and only if in every model in which  is true,  is also true or if  is true then  must also be true. Informally the truth of is contained in the truth of . 16. Define Validity of a sentence A sentence is valid or necessarily true if and only if it is true under all possible interpretation in all possible worlds 17. Define Satistiability of a sentence A sentence is satisfiable if and only if there is some interpretation in some world for which it is true. 18.What are the basic Components of propositional logic? i. Logical Constants (True, False) 19. What is truth preserving? An inference algorithm that derives only entailed sentences is called sound or truth preserving. 20. Define a Complete inference procedure An inference procedure is complete if it can derive all true conditions from a set of premises.

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21. Define Interpretation Interpretation specifies exactly which objects, relations and functions are referred to by the constant predicate, and function symbols 22. What is first-order logic? The first-order logic is sufficiently expressive to represent a good deal of our common sense knowledge. It also either subsumes or forms the foundation of many other representation languages. 23. Define resolution Resolution is such a procedure, which gains its efficiency from the fact that it operates on statements that have been converted to a very convenient standard form. 24. What are the three levels in describing knowledge based agent? The three levels in describing knowledge based agent  Logical level;  Implementation level;  Knowledge level or epistemological level. 25. Define Frames

Frames are descriptions of conceptual individuals Frames are essentially defined by their relationships with other frames. It is a collection of attributes and associated values that describe some entity in the world 26. Define Semantic nets A semantic network, or frame network, is a network which represents semantic relations between concepts. This is often used as a form of knowledge representation. It isa directed or undirected graph consisting of vertices, which represent concepts, and edges. Semantic nets initially used to represent labeled connection between two nodes 27. Define strong slot filler structure Strong slot and filler structures typically represents links between objects according to more rigid rules .They provide specifications of what type of objects and relations between objects and are usually used to represent knowledge about common situations

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