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While hyperlinks have come into widespread use, the closely related semantic link is not yet widely used. The numeric table has been used since Babylonian times. More recently, these tables have been used to represent logic operations, as truth tables, which were used to study and model Boolean logic, for example. Spreadsheets are yet another tabular representation of knowledge. Other knowledge representations are treeThis article is about the biological organisms known as trees. For other meanings of the word see tree (disambiguation). oak tree in Denmark A tree can be defined as a large perennial woody plant. Though there is no set definition of size, it is generallys, which echoes the Biblical tree of knowledge.
One problem in knowledge representation consists of how to store and manipulate knowledgeKnowledge is the awareness and understanding of facts, truths or information gained in the form of experience or learning. Knowledge is an appreciation of the possession of interconnected details which, in isolation, are of lesser value. Knowledge is a te in an information system in a formal way so that it may be used by mechanisms to accomplish a given task. Examples of applications are expert systemAn expert system is a class of computer programs developed by researchers in artificial intelligence during the 1970s and applied commercially throughout the 1980s. In essence, they are programs made up of a set of rules that analyze information (usuallys, machine translation systems, computer-aided maintenanceThe first computer-aided maintenance software came from DEC in the 1980s to configure VAX computers. The software was built using the techniques of artificial intelligence expert systems, because the problem of configuring a VAX required expert knowledge. systems and information retrievalInformation retrieval (IR is the art and science of searching for information in documents, searching for documents themselves, searching for metadata which describes documents, or searching within databases, whether relational stand alone databases or hy systems (including database front-ends).
Some people think it would be best to represent knowledge in the same way that it is represented in human mind, which is the only known working intelligenceIntelligence is a general mental capability that involves the ability to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn. While the definition and importance of intelligence is an issue of some controversy, especia so far, or to represent knowledge in the form of human language. Unfortunately, we don't know how knowledge is represented in the human mind, or how to manipulate human languages in the same way as the human mind.
For this reason, various artificial languages and notations have been proposed for representing knowledge. They are typically based on logic and mathematics, and have easily parsed grammars to ease machine processing.
The recent fashion in knowledge representation languages is to use XML as the low-level syntax. This tends to make the output of these KR languages easy for machines to parse, at the expense of human readability.
First-order predicate calculus is commonly used as a mathematical basis for these systems, to avoid excessive complexity. However, even simple systems based on this simple logic can be used to represent data which is well beyond the processing capability of current computer systems: see computability for reasons.Examples of notations:
Examples of artificial languages intended for knowledge representation include: