Database DesignDatabase Design FormalismsObject Definition LanguageODL Class DeclarationsODL ExampleODL DeclarationsSlide 7Slide 8Slide 9Slide 10Types in ODLAllowable Types in ODLDatabase Design•Why do we need it?– Agree on structure of the database before deciding on a particular implementation.•Consider issues such as:–What entities to model–How entities are related–What constraints exist in the domain–How to achieve good designsDatabase Design Formalisms•Object Definition Language (ODL):– Closer in spirit to object-oriented models•Entity/Relationship model (E/R):–More relational in nature.•Both can be translated (semi-automatically) to relational schemas (with varying amount of pain).•ODL to OO-schema: direct transformation (C++ or Smalltalk based system).Object Definition Language•Is part of ODMG, which also gave us OQL. •Resembles C++ (and Smalltalk).•Basic design paradigm in ODL: –Model objec ts and their properties.•For abstraction purposes:–Group objects into classes.•What qualifies as a good class?–Objects should have common properties.ODL Class DeclarationsInterface <name> { attributes: <type> <name>; relationships <range type> <name>; methods}Method example: float gpa(in: Student) raises (noGrades)Arbitrary function can compute the value of gpa, based on astudent object given as input.ODL ExampleProductPersonCompanycategorynamepricenamestockpricenameaddress ssnODL DeclarationsInterface Product { attribute string name; attribute float price; attribute enum Categories {electronics, communications, sports …} category }Interface Company { attribute string name; attribute float stockprice; }Interface Person { attribute integer ssn; attribute string name; attribute Struct Address {string street, string city} address; }ODL ExampleProductPersonCompanycategorynamepricenamestockpricenameaddress ssnbuysworksFormadeByODL DeclarationsInterface Product { attribute string name; attribute float price; attribute enum Categories {electronics, communications, sports …} category; relationship <Company> madeBy; }Interface Person { attribute integer ssn; attribute string name; attribute Struct Address {string street, string city} address; relationship set <Product> buys; relationship set <Company> worksFor;}ODL ExampleProductPersonCompanycategorynamepricenamestockpricenameaddress ssnbuysworksFormadeByemploysmakesODL DeclarationsInterface Company { attribute string name; attribute float stockprice; relationship set <Product> makes inverse Product::madeBy; relationship set <Person> employs inverse Person::worksFor; }Types in ODLBasic types: Atomic types (e.g., string, integer, …) Interface types (e.g., Person, Product, Company)Constructors: Set: (1, 5, 6) Bag: (1, 1, 5, 6, 6 ) List: (1, 5, 6, 1, 6 ) Array: Integer[17] Struct: {string street, string city, integer zipcode}Allowable Types in ODLFor attributes: start with atomic or struct, and apply a collection type. OK: string, set of integer, bag of Address. Not OK: Product, set of set of integer.For relationships: start with interface type and apply a collection type. OK: Product, set of Product, list of Person. Not OK: struct {pname Product, cname Company} set of bag of Product
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