Acct 316 Acct 316 Acct 316 Data Modeling and Database Design 5 UAA – ACCT 316 Accounting Information Systems Dr. Fred Barbee Chapter

Acct 316 Acct 316 Acct 316 Hmmm? What is data modeling?

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 The Blind Men and the Elephant

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 So what! You Say!

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 Without a model of what we are building, we are like these blind men: we may be partly right, but we are probably mostly wrong.

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 The elephant – a third grader’s view.

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 You cannot understand (and thus represent) something unless you comprehend it completely – enterprise-wide.

What is Data Modeling? ACCT 316 ACCT 316 ACCT 316 Plato’s “Myth of the Cave”

Acct 316 Acct 316 Acct 316 Hmmm? What is data modeling?

Acct 316 Acct 316 Acct 316 The Text Definition... Data modeling is the process of defining a database so that it faithfully represents all aspects of the organization, including its interactions with the external environment.

Acct 316 Acct 316 Acct 316 Other Definitions... Data modeling is the task of formalizing the data requirements of the business process as a conceptual model. Hall, James A. Accounting Information Systems Southwestern Publishing, 2001

Acct 316 Acct 316 Acct 316 Other Definitions... Data modeling is the process of defining what data you want to capture in your database and the relationships between data. Database Services University of Michigan

Acct 316 Acct 316 Acct 316 Data Modeling and Database Design 5 Database Design Process Chapter

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Data Modeling Occurs Here Figure 5-1

Let’s At each of these steps individually. The Database Design Process ACCT 316 ACCT 316 ACCT 316

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Initial planning to determine the need for and feasibility of developing a new system.

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Identifying User Needs

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Developing the contextual- external- and internal-level schemas

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Translating the internal-level schema into the actual database structures that will be implemented in the new system.

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Transferring all data from the existing system to the new database.

Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Using and maintaining the new system.

Acct 316 Acct 316 Acct 316 The Entity-Relationship (E-R) Diagram

ACCT 316 ACCT 316 ACCT 316 Entity Relationship

Acct 316 Acct 316 Acct 316 The REA Data Model

Acct 316 Acct 316 Acct 316 The REA Data Model The REA data model is a conceptual modeling tool specifically designed to provide structure for designing AIS data bases.

Acct 316 Acct 316 Acct 316 The REA Data Model The REA data model provides structure in two ways: By identifying what entities should be included in the AIS database By prescribing how to structure relationships among the entities in the AIS database

Basic REA template

The REA Data Model ACCT 316 ACCT 316 ACCT 316 ResourcesEventsAgents Give-To- Get Duality

The REA Data Model ACCT 316 ACCT 316 ACCT 316 ResourcesEventsAgents Resources : Those things that have economic value to the firm.

The REA Data Model ACCT 316 ACCT 316 ACCT 316 ResourcesEventsAgents Events : Various Business Activities

The REA Data Model ACCT 316 ACCT 316 ACCT 316 ResourcesEventsAgents Agents: People and Organizations that participate in events.

Acct 316 Acct 316 Acct 316 Developing an REA Diagram

Acct 316 Acct 316 Acct Step 1: Identify the Economic Exchange Events Identify the pair of events that reflect the basic economic exchange (give-to-get duality relationship) in that cycle.

Identify the PAIR of events One GET One GIVE

Acct 316 Acct 316 Acct Step 2: Identify Resources and Agents Identify the Resources affected by each event and the agents who participate in those events.

Identify... RESOURCES affected by each event. AGENTS who participate in the events.

Acct 316 Acct 316 Acct Step 3: Include commitment Events Analyze each economic exchange event to determine whether it should be decomposed into a combination of one or more commitment events and an economic exchange event.

Include commitment events.

Acct 316 Acct 316 Acct Determine the cardinalities of each relationship. Step 4: Determine Cardinalities of Relationships

Determine cardinalities of relationships.

SalesCustomer How many sales transactions can be linked to each individual customer? How many customers can be linked to each individual sales transaction?

Cardinalities ACCT 316 ACCT 316 ACCT 316 (1,N) Minimum Maximum

The first number is the minimum cardinality. It indicates whether a row in this table must be linked to at least one row in the table on the opposite side of that relationship.

Acct 316 Acct 316 Acct 316 Minimum Cardinality The minimum cardinality of a relationship indicates whether each row in that entity MUST be linked to a row in the entity on the other side of the relationship. Minimum cardinalities can be either 0 or 1.

Acct 316 Acct 316 Acct 316 Minimum Cardinalities A minimum cardinality of zero means that a new row can be added to that table without being linked to any rows in the other table. A minimum cardinality of one means that each row in that table MUST be linked to at least one row in the other table

Cardinalities ACCT 316 ACCT 316 ACCT 316 Sales Made to Customer (0, N) The minimum cardinality of zero in the (0, N) cardinality pair to the left of the customer entity in the customer-sales relationship indicates that a new customer may be added to the database without being linked to any sales events.

Cardinalities ACCT 316 ACCT 316 ACCT 316 The minimum cardinality of 1 in the (1,1) cardinality pair to the right of the sales entity in the customer-sales relationship indicates that a new sales transaction CAN ONLY be added if it is linked to a customer. Sales Made to Customer (0, N) (1,1)

The second number is the maximum cardinality. It indicates whether one row in that table can be linked to more than one row in the other table.

Acct 316 Acct 316 Acct 316 Maximum Cardinalities The maximum cardinality of a relationship indicates whether each row in that entity CAN be linked to more than one row in the entity on the other side of the relationship. Maximum cardinalities can be either 1 or N.

Acct 316 Acct 316 Acct 316 Maximum Cardinalities A maximum cardinality of 1 means that each row in that table can be linked to at most only 1 row in the other table. A maximum cardinality of N means that each row in that table MAY be linked to more than one row in the other table.

Cardinalities ACCT 316 ACCT 316 ACCT 316 Sales Made to Customer (0, N) The maximum cardinality of N in the (0,N) cardinality pair to the left of the customer entity in the customer-sales relationship indicates that a given customer MAY be linked to many sales events.

Cardinalities ACCT 316 ACCT 316 ACCT 316 The maximum cardinality of 1 in the (1,1) cardinality pair to the right of the sales entity in the customer-sales relationship indicates that a given sales transaction can only be linked to one customer. Sales Made to Customer (0, N) (1,1)

Acct 316 Acct 316 Acct 316 Determine Cardinalities Cardinalities are not arbitrarily chosen by the database designer. They reflect facts about the organization being modeled and its business practices obtained during the requirements analysis stage of the database design process.

Acct 316 Acct 316 Acct 316 Cardinalities: Types of Relationships Three basic types - depending on the maximum cardinality associated with each entity. A one-to-one relationship (1:1) A one-to-many relationship (1:N) A many-to-many relationship (M:N)

Types of Relationships ACCT 316 ACCT 316 ACCT 316 Panel A: One-to-One (1:1) Relationship Sales Cash Receipts (0,1)(1,1)

Types of Relationships ACCT 316 ACCT 316 ACCT 316 Panel B: One-to-Many (1:N) Relationship Sales Cash Receipts (0,N)(1,1)

Types of Relationships ACCT 316 ACCT 316 ACCT 316 Panel C: One-to-Many (1:N) Relationship Sales Cash Receipts (0,1)(1,N)

Types of Relationships ACCT 316 ACCT 316 ACCT 316 Panel D: Many-to-Many (M:N) Relationship Sales Cash Receipts (0,N)(1,N)

Acct 316 Acct 316 Acct 316 Build a Set of Tables to Implement an REA Model of an AIS in a Relational Database

Acct 316 Acct 316 Acct 316 Implementing an REA Diagram in a Relational Database An REA diagram can be used to design a well-structured relational database. A well-structured relational database is one that is not subject to update, insert, and delete anomaly problems.

Acct 316 Acct 316 Acct 316 Three Step Process Create a table for each distinct entity and for each many-to many relationship Assign attributes to appropriate tables Use foreign keys to implement one- to-one and one-to-many relationships

Implementing an REA Diagram ACCT 316 ACCT 316 ACCT 316

Implementing an REA Diagram ACCT 316 ACCT 316 ACCT 316

Implementing an REA Diagram ACCT 316 ACCT 316 ACCT 316