Chapter 3: Modeling Data in the Organization Database for Information System Fall 2012 Mr. Mohammed Rafiq Section: 201 Chapter Presentation (10%) Presented by: Farah AlSharif 200900901 Chapter 3: Modeling Data in the Organization

Outline The Definition and Characteristics of Business Rule Data ER- Modeling Diagram The Components of Entity Relationship Diagram Types of Entities Types of Attributes Relationship Degrees Example of ERD

What is a Business Rule? What is a business rule? A business rule defines or constrains one aspect of a business that is intended to assert business structure or influence the behavior of your business. Business Rules Characteristics Atomic Business statements Declarative Constraining Expressed in natural language Traceable

What is a Data? Data: Facts and statistics collected together for reference or analysis. Good Data Name Characteristics Related to business, not technical, characteristics Meaningful and self-documenting Unique Readable Composed of words from an approved list Repeatable Follows standard syntax

What is ER-Modeling? ER-modeling is a data modeling technique used in software engineering to produce a conceptual data model of a information system Diagrams created using this ER-modeling technique are called: Entity Relationship Diagram ERD typically consists of four different graphical components: Entities Attributes Relationships Cardinalities

What is ER-Modeling? (continued) Entities: Entity instance–person, place, object, event, concept (often corresponds to a row in a table) Attributes: property or characteristic of an entity or relationship type (often corresponds to a field in a table) Employ Project Employee-ID Project-Name

Types of entities Exist independently of other types of entities Strong entities Exist independently of other types of entities Has its own unique identifier Identifier underlined with single line Weak entity Dependent on a strong entity (identifying owner)…cannot exist on its own Does not have a unique identifier Partial identifier underlined with double line Entity box has double line Associative Entity All relationships for the associative entity should be many. The associative entity could have meaning independent of the other entities. Strong Weak Weak Associative

Types of attributes: Key Attributes – Uniquely identify instance of a corresponding entity set Multivalued Attributes – attributes that may contain multiple values Simple Attributes – Cannot be subdivide Composite Attributes – attributes that contains meaningful component parts Derived Attributes – attributes whose values are computed from other data in the database

Relationships & Cardinalities Relationship instance–link between entities (corresponds to primary key-foreign key equivalencies in related tables) Cardinality: Cardinality constrains-the number of instances of one entity that can or must be associated with each instance of another entity Minimum Cardinality If zero, then optional If one or more, then mandatory Maximum Cardinality The maximum number Employ Relationship

Degrees of a Relationship A degree of a relationship is the number of entity types that participate in it The Degrees are: Unary Relationship One entity related to another of the same entity type Binary Relationship Entities of two different types related to each other Ternary Relationship Entities of three different types related to each other

Degrees of a Relationship (continued) Binary Unary Ternary

ERD Example

References Jones, B. (2010, December 5). E-R Diagrams. University of Missouri- St. Louis. Retrieved December 9, 2012, from http://www.umsl.edu/~bcjtz4/umsl/er_diag Interpreting Entity-Relationship Diagrams. (n.d.). Welcome to Phil Block's Personal Web Site. Retrieved December 9, 2012, from http://www.philblock.info/hitkb/i/interpreting_entity- relationship_diagrams.html

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