3 - 1 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] CIS 8040 – Semantic Data Modeling Conceptual Modeling Outline What is Conceptual Data Modeling Entity-Relationship (E-R ) Modeling Limitations of E-R Modeling Object-oriented Modeling: Another semantic model (discussed later in this course)3 - 2 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] What Is Conceptual Data Modeling? A process that represents the entities, relationships, and activities of an enterprise in terms of a set of abstract concepts of a chosen data model for specific purposes. Enterprise Modeling, Business Modeling Conceptual Perception of an Enterprise Bridge the Gap STUDENT( ID, Name, Age, Address, GPA ) INSTRUCTOR ( Emp#, Name, Rank, Dept ) COURSE ( Course#, Credits, Title ) CLASS ( Emp#, ID, Course#, Time, Room )3 - 3 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Data Semantics Static Information  Data -- Entities  Associations -- Relationships among entities Dynamic Information  Activities -- Operations/transactions  Integrity constraints -- Business rules/regulations and data meanings Conceptual Data Model Revisited A conceptual data model consists of:  A collection of formal concepts  A set of usage rules Different models have different modeling capability Conventional data modeling Semantic data modeling Object-Oriented data modeling -- Hierarchical -- Network -- Relational -- E-R -- EER -- etc. -- Relational3 - 4 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Entity Relationship (E-R) Modeling Introduced by Peter Chen in 1976 Basic modeling concepts:  Entities, entity types, and attributes  Relationships InstructorOfficeAssigned1 1 DepartmentWorks_forN 1 Teaches N M CourseDateLanguageEmp#NameFNameMInitLNameTimeLocationDateE-R Notation (there is no standard) Entity Relationship Attribute Primary Key3 - 5 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Entities An entity is a conceptual object Physically exists  Usually a noun in requirements specification Jose Alice Steve CIS 8040 CIS 3730 Acct CIS Student Class Department Entity Types A collection of similar entities An abstraction of "physical" entities  A noun in requirement specifications  Has "independent" meaning Student Course Department Jose Alice Steve CIS 8040 CIS 3730 Acct CIS3 - 6 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Attributes Properties or characteristics of entities and entity types (Attributes do not describe!)  Attribute values – Property values of entities which describe the entities  Value set - All acceptable attribute values  Attributes (definitions) -- Properties of entity types A noun or an adjective in requirement specifications No "independent" meaning ID Student Age Jose "123-45-6789" 25 Key Attributes  One or a group of attributes that can uniquely identify individual entities of an entity type  A key refers to one or a group of attributes as a whole  A key attribute is a component attribute of a key  Key changes with data semantics  An entity type may have several qualified keys  Primary key -- One of the candidate keys  Alternate key - Candidate keys not used as the primary key  Secondary key -- An identifier of records with similar properties of interest  The primary key attribute(s) is(are) underlined3 - 7 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] More Attributes Simple attribute Contains atomic values only Composite attribute Has component attributes _____________________________________ Single-valued attribute Has exactly one value per entity Multi-valued attribute Contains repeating values per entity _____________________________________ Derived Attribute can be created from existing attributes Student id age name degrees Fname Mname Lname StartDate YearsAttended Relationships Associations among entities  Relationships -- Associations among entities Usually a verb in requirement specification Student Course Takes Course Student Takes Joseph Alice Sue Tom Peter . . . CIS2010 CIS3210 CIS8600 CIS3730 CIS8140 . . . Occurrence Diagram3 - 8 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Relationship Cardinality (Occurrence diagram shown below) How entities are connected through a relationship  One-to-One -- An entity of E1 is connected to at most one entity of E2 and vice versa.  One-to-Many -- An entity of E1 may be connected to one or more entities of E2, but an entity of E2 can only be mapped to at most one entity of E1.  Many-to-Many -- An entity of E1 may be linked to one or more entities of E2, and vice versa. [ ][ ][ ]...abc...xyz...[ ][ ][ ]...abc...xyz......abc...xyz...E1 E2 R 1 1 1 M M N Structural Constraints • Main type of constraint on relationships is called multiplicity. • Multiplicity - number (or range) of possible occurrences of an entity type that may relate to a single occurrence of an associated entity type through a particular relationship. • Represents policies (called business rules) established by user or company.3 - 9 Copyright © 2012 Robinson College of Business, Georgia State University David S. McDonald Director of Emerging Technologies Tel: 404-413-7368; e-mail: [email protected] Multiplicity  The minimum and maximum number of entities participating in the relationship  Must be shown in both directions Relationship Degrees The number of