4.1 KNOWLEDGE-BASED EVALUATION FOR DESIGN
The concepts of object-oriented languages can be found throughout the domains of artificial intelligence and information management. Table 7 correlates the concepts with key terms.
An entity or class is a grouping of objects which have a set of common attributes. Within a database or a spreadsheet, the class or entity would correlate to table or file respectively. An instance for our purposes is a manifestation or object of the class which would correspond to a row within a database. The instance in turn consists of attributes which are also known as properties. These attributes are usually inherited from the entity description, as seen in Figure 23 above.
Each property of an object has an associated value. This value may be considered an object in its own right. The location of this value is known as the slot or instance variable. The location and value correspond to a data base's field and datum respectively.
Some object-oriented constructs allow the objects in a property slot to have their own internal state [Kim 87]. In effect, an object may be constructed of other objects. Nexpert Object only uses the primitive object types of strings, integers, floating values, "datetime", and boolean.
PIMES' rules are generic in the sense that their conditions do not contain explicit information. Rather, the conditions are primarily comparisons or list narrowing functions that utilize facts from outside the knowledge base. Within PIMES a distinction between facts and knowledge is attempted. Generally, a fact is a number or value and is stored within a data base. Knowledge from the knowledge base is a generic template into which facts are placed and meaning is inferred.
Information may be obtained from the feature graph or from the Relational Database Management System (RDMS). Assessments generated by PIMES are stored either in a RDBMS or a specially formatted "flat" ASCII file. As such, PIMES assessments can be retrieved with facilities already within the RDBMS.
There can be a direct mapping between information from a relational database and an object frame. As illustrated by Table 1, entity, instance, attribute and datum can be used to completely communicate information across relational database and frame-base representations.
Concept Nexpert Object DBMS
Entity Class Table
Instance Object Row
Attribute Property Slot Column
Datum Value Value