Database Systems Background Review (2) Dr. Muhammad Shafique ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Outline Database Development Data Modeling ER Model EER Model Relational Data Model ICS 541 - 01 (072) Database Systems Background Review

Overview of Database Design Process Two main activities: Database design Applications design To design the conceptual schema for a database application To design the programs and interfaces that interact with the database Generally considered part of software engineering ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Database Development ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Data Modeling Categories of data models Conceptual (high-level, semantic) data models Provide concepts that are close to the way many users perceive data. Also called entity-based or object-based data models Implementation (representational) data models Provide concepts that fall between the above two, used by many commercial DBMS implementations Relational data model Physical (low-level, internal) data models Provide concepts that describe details of how data is stored in the computer. ICS 541 - 01 (072) Database Systems Background Review

Data Modeling Using ER Model (1) ER Model Concepts Entity Entity Types, Value Sets, and Key Attributes Weak Entity Types Attribute Categories of Attributes Simple Composite Multi-valued Relationship Relationship Types Roles and Attributes in Relationship Types ICS 541 - 01 (072) Database Systems Background Review

Data Modeling Using ER Model (2) ICS 541 - 01 (072) Database Systems Background Review

Relationships of Higher Degree Relationship types of degree 2 are called binary Relationship types of degree 3 are called ternary and of degree n are called n-ary In general, an n-ary relationship is not equivalent to n binary relationships Constraints are harder to specify for higher-degree relationships (n > 2) than for binary relationships ICS 541 - 01 (072) Database Systems Background Review

Ternary Relationships ICS 541 - 01 (072) Database Systems Background Review

Another example of a ternary relationship ICS 541 - 01 (072) Database Systems Background Review

Some of the Currently Available Automated Database Design Tools COMPANY TOOL FUNCTIONALITY Embarcadero Technologies ER Studio Database Modeling in ER and IDEF1X DB Artisan Database administration, space and security management Oracle Developer 2000/Designer 2000 Database modeling, application development Popkin Software System Architect 2001 Data modeling, object modeling, process modeling, structured analysis/design Platinum (Computer Associates) Enterprise Modeling Suite: Erwin, BPWin, Paradigm Plus Data, process, and business component modeling Persistence Inc. Pwertier Mapping from O-O to relational model Rational (IBM) Rational Rose UML Modeling & application generation in C++/JAVA Resolution Ltd. Xcase Conceptual modeling up to code maintenance Sybase Enterprise Application Suite Data modeling, business logic modeling Visio Visio Enterprise Data modeling, design/reengineering Visual Basic/C++ ICS 541 - 01 (072) Database Systems Background Review

Enhanced-ER (EER) Model (1) EER stands for Enhanced ER or Extended ER EER Model Concepts Includes all modeling concepts of basic ER Additional concepts: Subclasses/superclasses Specialization/generalization Categories (UNION types) Attribute and relationship inheritance The additional EER concepts are used to model applications more completely and more accurately EER includes some object-oriented concepts, such as inheritance ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Subclasses and Superclasses ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Specialization ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Generalization ICS 541 - 01 (072) Database Systems Background Review

Specialization/Generalization Constraints Two basic constraints on specialization/generalization Disjointness Constraint: Completeness Constraint ICS 541 - 01 (072) Database Systems Background Review

Example of disjoint partial Specialization ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Example of overlapping total Specialization ICS 541 - 01 (072) Database Systems Background Review

Specialization / Generalization Lattice Example (UNIVERSITY) ICS 541 - 01 (072) Database Systems Background Review

Example of Categorization (Union Type) ICS 541 - 01 (072) Database Systems Background Review

Formal Definitions of EER Model (1) Class C: A type of entity with a corresponding set of entities: The definition of relationship type in ER/EER should have 'entity type' replaced with 'class‘ to allow relationships among classes in general Subclass S is a class whose: Type inherits all the attributes and relationship of a class C Set of entities must always be a subset of the set of entities of the other class C S ⊆ C C is called the superclass of S A superclass/subclass relationship exists between S and C ICS 541 - 01 (072) Database Systems Background Review

Formal Definitions of EER Model (2) Specialization Z: Z = {S1, S2,…, Sn} is a set of subclasses with same superclass G Hence, G/Si is a superclass relationship for i = 1, …., n. G is called a generalization of the subclasses {S1, S2,…, Sn} Z is total if we always have: S1 ∪ S2 ∪ … ∪ Sn = G; Otherwise, Z is partial. Z is disjoint if we always have: Si ∩ S2 empty-set for i ≠ j; Otherwise, Z is overlapping. ICS 541 - 01 (072) Database Systems Background Review

Formal Definitions of EER Model (3) Subclass S of C is predicate defined if predicate (condition) p on attributes of C is used to specify membership in S; that is, S = C[p], where C[p] is the set of entities in C that satisfy condition p A subclass not defined by a predicate is called user-defined Attribute-defined specialization: if a predicate A = ci (where A is an attribute of G and ci is a constant value from the domain of A) is used to specify membership in each subclass Si in Z Note: If ci ≠ cj for i ≠ j, and A is single-valued, then the attribute-defined specialization will be disjoint. ICS 541 - 01 (072) Database Systems Background Review

Formal Definitions of EER Model (4) Category or UNION type T A class that is a subset of the union of n defining superclasses D1, D2,…Dn, n > 1: T ⊆ (D1 ∪ D2 ∪ … ∪ Dn) Can have a predicate pi on the attributes of Di to specify entities of Di that are members of T. If a predicate is specified on every Di T = (D1[p1] ∪ D2[p2] ∪…∪ Dn[pn]) ICS 541 - 01 (072) Database Systems Background Review

Conceptual Modeling Concepts Semantic data models and Knowledge Representation (KR) Similarities Both use an abstraction process Both provide concepts, constraints. Operations, and languages for defining data and representing knowledge Differences KR is broader in scope than semantic data models KR schemes include reasoning mechanisms KR schemes mix up schemas with instances whereas semantic data models focus on the representation of database schemas ICS 541 - 01 (072) Database Systems Background Review

Conceptual Modeling Concepts Abstraction concepts Classification and Instantiation Is-an-instance-of or is-a-member-of Exceptions Class properties Meta-class concept Identification Two levels of identification To distinguish among database objects and classes To identify database objects and to relate them to their real-world counterparts ( same person in different roles) ICS 541 - 01 (072) Database Systems Background Review

Conceptual Modeling Concepts Abstraction concepts Specialization and generalization Is-a or Is-a-subclass-of CONSTRAINTS CARDINALITY (Min and Max) COVERAGE (Total vs. Partial, and Exclusive (disjoint) vs. Overlapping) Aggregation and association To build composite objects Three scenarios Entity as an aggregation of attributes Association relationship to relate objects from several independent classes (explained with example in the following slides) Combining related objects to define higher level objects IS-A-PART-OF or IS-A-COMPONENT-OF ICS 541 - 01 (072) Database Systems Background Review

Modeling Aggregation (1) Example: Company, Job_applicant, and Job_Offer ICS 541 - 01 (072) Database Systems Background Review

Modeling Aggregation (2) ICS 541 - 01 (072) Database Systems Background Review

Modeling Aggregation (3) ICS 541 - 01 (072) Database Systems Background Review

Modeling Aggregation (4) ICS 541 - 01 (072) Database Systems Background Review

Modeling Aggregation (5) ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Ontologies Ontology is “a specification of a conceptualization” Specification refers to the language and vocabulary terms (data model concepts) used to specify conceptualization Conceptualization refers to the set of concepts that are used represent the reality or knowledge that is of interest to a community of users Some possible descriptions of ontology Dictionary --- describes relationships between words Database schems Many medical, scientific, and engineering ontologies are being developed as a means of standardizing concepts and terminology Semantic Web --- for meaningful information exchange ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review References Textbook Chapter 3 Textbook Chapter 4 Semantic Database Modeling: Survey, Applications, and Research Issues Richard Hull and Roger King ACM Computing Surveys, Vol. 19, No. 3, September 1987 Semantic Data Models Joan Peckham and Fred Maryanski ACM Computing Surveys, Vol. 20, No. 3, September 1988, pp 153 – 189 ICS 541 - 01 (072) Database Systems Background Review

Database Systems Background Review Summary Data Modeling ER Model EER Model Other data models (reading material) ICS 541 - 01 (072) Database Systems Background Review