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PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – UNIVERSITY OF INDONESIA
PERANCANGAN SISTEM INFORMASI
Session 5 Data Modeling
Based on System Analysis & Design 2nd EditionAuthors : Alan Dennis & Barbara Haley Wixom
Publisher : John Wiley & Sons
Session 5 Data ModelingSession 5 Data Modeling
Based on System Analysis & Design 2nd EditionAuthors : Alan Dennis & Barbara Haley Wixom
Publisher : John Wiley & Sons
2PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
ObjectivesObjectives
Understand the rules and style guidelines for creating entity relationship diagrams.Be able to create an entity relationship diagram.Become familiar with the data dictionary and metadata.Become familiar with the process of normalization.Understand how to balance between entity relationship diagrams.
3PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Key DefinitionsKey Definitions
Data modelA formal way of representing the data that are used and created by a business systemShows the people, places and things about which data is captured and the relationships among them.
Logical data modelshows the organization of data without indicating how it is stored, created, or manipulated
4PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Key DefinitionKey Definition
Physical data modelshows how the data will actually be stored in databases or files.
Normalization is the process analysts use to validate data models.Data models should balance with process models
5PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
THE ENTITY-RELATIONSHIP DIAGRAM (ERD)
6PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
What Is an ERD?What Is an ERD?
A picture showing the information created, stored, and used by a business system. Entities generally represent similar kinds of informationLines drawn between entities show relationships among the dataHigh level business rules are also shown
7PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Using the ERD to Show Business RulesUsing the ERD to Show Business Rules
Business rules are constraints that are followed when the system is in operation.ERD symbols can show when one instance of an entity must exist for an instance of another to exist
A doctor must exist before appointments the doctor can be made
8PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
An ERD ExampleAn ERD Example
9PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
ERD ElementsERD Elements
10PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
EntityEntity
A person, place, event, or thing about which data is collectedMust be multiple occurrences to be an entity
Example: If a firm has only one warehouse, the warehouse is not an entity. However, if the firm has several warehouses, the warehouse could be an entity if the firm wants to store data about each warehouse instance.
11PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Entities and InstancesEntities and Instances
12PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Case Repository Entry for Patient EntityCase Repository Entry for Patient Entity
13PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
AttributesAttributes
Information captured about an entityOnly those used by the organization should be included in the modelAttribute names are nounsSometimes entity name is added at the beginning of the attribute name for clarity
14PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
IdentifiersIdentifiers
One or more attributes can serve as the entity identifier, uniquely identifying each entity instanceConcatenated identifier consists of several attributesAn identifier may be ‘artificial,’ such as creating an ID numberIdentifiers may not be developed until the Design Phase
15PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Identifier TypesIdentifier Types
16PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Case Repository Entry for Patient_SSNAttributeCase Repository Entry for Patient_SSNAttribute
17PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
RelationshipsRelationships
Associations between entitiesThe first entity in the relationship is the parententity; the second entity in the relationship is the child entityRelationships should have active verb namesRelationships go in both directions
18PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
CardinalityCardinality
Cardinalityrefers to the number of times instances in one entity can be related to instances in another entity• One instance in an entity refers to one and only
one instance in the related entity (1:1)• One instance in an entity refers to one or more
instances in the related entity (1:N)• One or more instances in an entity refer to one or
more instances in the related entity (M:N)
19PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
ModalityModality
ModalityRefers to whether or not an instance of a child entity can exist without a related instance in the parent entity• Not Null means that an instance in the related
entity must exist for an instance in another entity to be valid
• Null means that no instance in the related entity is necessary for an instance in another entity to be valid
20PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Case Repository Entry for a RelationshipCase Repository Entry for a Relationship
21PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
The Data Dictionary and MetadataThe Data Dictionary and Metadata
Metadata is information stored about components of the data modelMetadata is stored in the data dictionary so it can be shared by developers and users throughout the SDLCA complete, shareable data dictionary helps improve the quality of the system under development
22PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
CREATING AN ENTITY-RELATIONSHIP DIAGRAM
23PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
ERD BasicsERD Basics
Drawing the ERD is an iterative process of trial and revisionERDs can become quite complex
24PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Steps in Building ERDsSteps in Building ERDs
Identify the entitiesAdd appropriate attributes for each entityDraw the relationships that connect associated entities
25PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Identify the EntitiesIdentify the Entities
Identify major categories of informationIf available, check the process models for data stores, external entities, and data flowsCheck the major inputs and outputs from the use cases
Verify that there is more than one instance of the entity that occurs in the system
26PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Add Appropriate AttributesAdd Appropriate Attributes
Identify attributes of the entity that are relevant to the system under development
Check the process model repository entries for details on data flows and data storesCheck the data requirements of the requirements definitionInterview knowledgeable usersPerform document analysis on existing forms and reports
Select the entity’s identifier
27PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Draw the RelationshipsDraw the Relationships
Start with an entity and identify all entities with which it shares relationshipsDescribe the relationship with the appropriate verb phraseDetermine the cardinality and modality by discussing the business rules with knowledgeable users
28PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
ERD Building TipsERD Building Tips
Data stores of the DFD should correspond to entitiesOnly include entities with more than one instance of informationDon’t include entities associated with implementation of the system (they will be added later)
29PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Advanced SyntaxAdvanced Syntax
Independent EntitiesCan exist without the help of another entityIdentifiers created from the entity’s own attributesAttributes from other entities are not needed to uniquely identify instances of these entities
Non-identifying relationshipsRelationships with an independent child entity
30PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Advanced SyntaxAdvanced Syntax
Dependent EntitiesA child entity uses attributes from the parent entity as part or all of its identifiersAlso called associative entity
Identifying relationshipRelationships having a dependent child entity
31PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Advanced SyntaxAdvanced Syntax
32PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Advanced SyntaxAdvanced Syntax
Intersection EntitiesA new entity created to store information about two entities sharing an M:N relationship• Remove the M:N relationship between two entities
and insert new entity between them• Create two 1:N relationships: original entities are
parents to the new child intersection entity• Name the intersection entity
33PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Advanced SyntaxAdvanced Syntax
34PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
VALIDATING AN ERD
35PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Design GuidelinesDesign Guidelines
Best practices rather than rulesEntities should have many occurrencesAvoid unnecessary attributesClearly label all components Apply correct cardinality and modalityBreak attributes into lowest level neededLabels should reflect common business termsAssumptions should be clearly stated
36PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
NormalizationNormalization
Technique used to validate data modelsSeries of rules applied to logical data model to improve its organizationThree normalization rules are common
37PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Normalization StepsNormalization Steps
38PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Unnormalized EntityUnnormalized Entity
Begin with an entity fromthe logical data model
39PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
First Normal Form (1NF)First Normal Form (1NF)
Look for repeating groups of attributes and remove them into separate entities
40PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Second Normal Form (2NF)Second Normal Form (2NF)If an entity has a concatenated identifier, look for attributes that depend only on part of the identifier. If found, remove to new entity.
41PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Third Normal Form (3NF)Third Normal Form (3NF)Look for attributes that depend only on another nonidentifying attribute. If found, remove to new entity. Also remove any calculated attributes.
42PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
Balancing ERDs with DFDsBalancing ERDs with DFDs
All analysis activities are interrelatedProcess models contain two data components
Data flows and data stores
The DFD data components need to balance the ERD’sdata stores (entities) and data elements (attributes)Many CASE tools provide features to check for imbalanceCheck that all data stores and elements correspond between models
Data that is not used is unnecessaryData that has been omitted results in an incomplete system
Do not follow thoughtlessly -- check that the models make sense!
43PowerPoint Course Material for SCELE Graduate Program Information TechnologyFaculty of Computer Science – University of Indonesia
SummarySummary
The ERD is the most common technique for drawing data models. The building blocks of the ERD are:
Entities describe people, places, or thingsAttributes capture information about the entityRelationships associate data across entities
Intersection, dependent, and independent entities must be recognized.The ERD must be balanced with the DFD.