The Semantic Object Model Semantic Objects Creating Data Models with Semantic Objects Types of Objects Object-Oriented Programming and Semantic Objects Comparing the Semantic Object and the E-R Model

Semantic Objects A semantic object is a named collection of attributes that sufficiently describes a distinct identity. (Fig. 4-2 pg. 81) Object attributes can be: çSimple attributes with a single value e.g. InvoiceNumber çGroup attributes being composites of other attributes e.g. Address{Street, City, State, Zip}

çSemantic object attributes that establish a relationship between one semantic object and another. çPaired attributes always exist in pairs. Maximum and minimum cardinality of attributes Object instances Object identifier Attribute domains Semantic object view

Creating Data Models with Semantic Objects An Example: The Highline University Administration Database (Fig pg. 93) Object specifications (Fig pg. 94,95)

Types of Objects Simple objects only contain single-valued, nonobject attributes e.g. EQUIPMENT pg. 96 Composite objects contain one or more multivalued, nonobject attributes e.g. HOTEL-BILL pg. 97 Compound objects contain at least one object attribute e.g. EMPLOYEE pg. 100

Hybrid objects contain at least one multivalued group attribute (composite) that includes a semantic object attribute (compound) e.g. DORMITORY pg. 104 Fig pg. 106, 107 Association objects relate two or more objects and store data that is peculiar to that specific to that relationship e.g. FLIGHT pg. 109 Parent/Subtype objects and inheritance e.g. EMPLOYEE and MANAGER, PROGRAMMER pg. 112

Object-Oriented Programming and Semantic Objects Object-oriented programming (OOP) is a way of designing and coding programs. An OOP object is an encapsulated (complete) structure having both attributes and methods. Methods are programs that OOP objects use to process themselves e.g. a method to display itself, one to create itself, etc.

Polymorphism means that several versions of a method exist and the compiler determines which one is appropriate each time the method is called. Object-Oriented DBMS and object persistence, i.e., the structure of the object is written out to some permanent storage like the disk.

Comparing the Semantic Object and the E-R Model Both are tools for modeling the database. Difference in orientation: entities Vs. semantic objects. Semantic objects contain more metadata than entities. Is it just a matter of preference? (Fig ,34, pg. 118)