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Given a set of verbs, you can build a verbs diagram to graphically represent how a given verb is split. Basically, there are two kinds of relations: Composition, which refers to the fact that you need to carry out the actions into which the verb is split to complete a given action; and Subclass-of, which represents verbs hierarchies. Figure 12 graphically summarized a verbs diagram related to types of chemical bonds. The conditions tables specify a set of conditions to be satisfied before executing an action or a set of conditions to be guaranteed after the execution of an action. For each identified condition, you should specify: Condition name; Description in natural language of the meaning of the constraint; Attributes that participate in the condition, and Formal expression of the condition. 11.3.3. Conceptualization of Rules and Formulas In many domains, numerical values of instance attributes might be derived from numerical values of other attributes and constants by using formulas. A formula is conceptualized using a Table of Formulas. The standard definition of formulas includes: Formula name; Inferred attribute, which identifies the instance attribute that is calculated with the formula; Formula, which includes the mathematical formula to be used to calculate the inferred attribute; Description, which includes the theoretical foundations of the formula; Basic instance attributes, which refers to the list of instance attributes used by the formula to calculate the inferred attribute; Basic class attributes, containing the list of class attributes used to calculate the inferred attribute; Constants, which include the list of constants used by the formula to get the inferred attribute; Precision with which the number should be calculated (i.e., to two decimal places); Constraint, if the formula is appropriate for specific values of basic instance attributes, it is necessary to specify some conditions (i.e., the formula must no be used if the value of a basic instance attribute used as the divisor is zero); and References. Table 10 shows the definitions of the formula that calculates a value of the attribute "Density-At-20-Celsius-Degrees." Note that to infer its value, only values of instance attributes ("Atomic-Volume-At-20-Celsius-Degrees" and "Atomic-Weight") are used. In sum, METHONTOLOGY produces a conceptual model expressed as a set of well-defined intermediate representations that allow one to: (1) to ascertain whether an ontology is useful and usable for a given application without examining its source code; and (2) compare the scope and completeness of several ontologies, their reusability, and sharability by analyzing the knowledge expressed in each IR. 11.4. FORMALIZATIONIn this phase, you will transform the conceptual model into a formal model, that is, a semicomputable representation of the external world. Actually, the main task you perform in this phase is to select the knowledge representation system, such as: frame-oriented, conceptual graphs, relational representations, or description logic.
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