MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Lecture 4: Data Modeling Process Modeling MIS 210 Information Systems I

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Data Models

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Entity-Relationship Diagrams Data-oriented approach –uses the data and the relationships among data to model requirements –purpose is to show the data used in the system –good for modeling data stores from a DFD A representation of organizational data. –Shows the rules about the meanings and interrelationships among the data.

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. E-R Diagrams Defined –A graphical representation of an E-R model. –E-R model a detailed, logical representation of the entities, associations, and data elements for an organization or business area.

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. E-R Symbols Entity Attribute Relationship

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Terminology Entity –a “thing” in the real world –has an independent existence Attribute(s) –One specific piece of information about a thing –a property of the entity –has a value (or value set or domain) Cardinality –the number of instances of an entity that are associated with another entity –a single occurrence of an entity

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Data Entities An Entity is a thing the users need to know (i.e, record) something about.

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Types of Things

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Types of Attributes Identifier (primary key / key attribute) –An attribute (or attributes) selected as the unique, identifying characteristic for an entity. Foreign Key –An attribute (or attributes) in one database table that is the primary key in another database table

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Attributes and Their Values All videos/DVDs have the following attributes: Product ID number Product Name Product Description Category ID Supplier ID Serial Number Each video/DVD has a value for each attribute: 1 Woodstock Concert Other WRNRBR DVD19925C1

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Relationships Relationship –Naturally occurring association among specific things –Occur in two directions –Cardinality/multiplicity

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Relationships Degree of Relationship –number of entities that participate in that relationship Unary (recursive) –degree one –A relationship between instances of one entity. Binary –degree two –A relationship between instances of two entities Ternary –A relationship between instances of three entities

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Cardinality of Relationships

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Relationships and Cardinality

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Trucking….One Approach Truck carries Shipment Warehouses delivers to stored at Retail Stores 1 m m 1 m m *Truck ID Volume Weight *Shipment Number Shipment Volume Weight Destination Trips makes 1 m

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Trucking….Another Approach Truck carries Shipment Warehouses delivers to stored at Retail Stores 1 m m 1 m m Truck ID Volume Weight Shipment Number Shipment Volume Weight Destination Trips makes 1 m

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Data Dictionary

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Data Dictionary Defined “…the data dictionary collects and coordinates specific data terms, and it confirms what each term means to different people in the organization.” Kendall & Kendall

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Data Dictionary (aka, Project Repository) Repository for all primitive-level data structures and data elements within a system. Use information from DFDs or ERDs to create the DD DD details each of the data items, data flows, processes, etc. in a system For example: DD entry for data items would show characteristics such as size, type, description, ranges, etc.

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Process Models

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Process Modeling Focus on the internal structure and processes in the DFD Most popular models –Structured English –Decision Tables –Decision Trees

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Structured English Form of English used to specify the processes in a DFD Makes use of nouns and action verbs Similar to pseudocode

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Structured English Example End of Month Processing DO FOR EACH INVENTORY ITEM COUNT STOCK IN STOCK ROOM ENTER COUNT ON INVENTORY SHEET END DO

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Decision Tables Lays out the logic of complex problems where there are multiple actions based on multiple decisions. Four components –conditions –decision rules –actions –action entries

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Decision Tables The total possible number of decision rules represents the total possible combinations, or permutations, of the condition values For example, for yes or no values: number of decision rules = 2 n For three conditions with yes or no values number of decision rules = 2 n = 2 3 = 8

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Decision Tables For a range of values –example, age: 1=18 to 20, 2=21-30, 3=31-40, 4=41-50, 5=50 or over –five (5) values for this condition What if there are a combination of different values –yes or no values –five values –total possible values = 2 x 5=10

MIS 210 Fall 2004Sylnovie Merchant, Ph. D. Decision Trees A graphical representation of a decision structure. Difficult to use for a complex situation.