Download UML Specification for Data Modeling

Chapter 7 Database Design
 UML Specification for Data Modeling
 The Relational Data Model and Object Model
 Persistence Frameworks
 Database Design
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UML Specification for
Data Modeling
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7.1 UML Specification for Data Modeling
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UML Notation for Data Modeling
Modeling Associations in the Data Model
Modeling Aggregation in the Data Model
Modeling Inheritance in the Data Model
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UML Notation for Data Modeling
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Modeling Associations in the Data Model
 Associations between two persistent objects
are realized as foreign keys to the associated
objects.
 A foreign key is a column in one table which
contains the primary key value of associated
object
Course Offering table
Number
CourseOffering
678
- number : String
Course_ID
456789
Foreign Key
0..*
0..*
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Name
Primary Key
Description Number
Math 101
Algebra
Course table
Course
- name
- description
- number
5
456789
Modeling Aggregation in the Data Model
 Aggregation is also modeled using foreign
key relationships
 Using composition implements a cascading
delete constraint
Student table
Student.
Student_ID
- studentID : int
123456
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Primary Key
0..*
Schedule table
Schedule
- semester : Semester
Student_ID
123456
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Foreign Key
Semester
Spring 2001
Modeling Inheritance in the Data Model
 A data model does not support modeling
inheritance in a direct way
 Two options
 Use separate tables (normalized data)
 Duplicate all inherited associations and
attributes (de-normalized data)
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Modeling Inheritance in the Data Model - Example
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Modeling Inheritance in the Data Model - Example
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Modeling Inheritance in the Data Model - Example
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Modeling Inheritance in the Data Model - Example
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Modeling Inheritance in the Data Model - Example
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The Relational Data Model and
Object Model
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7.2 The Relational Data Model and Object Model
 The Relational Data Model
 The Object Model
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The Relational Data Model
The relational model is composed of entities and relations.
An entity may be a physical table or a logical projection of
several tables also known as a view.
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The Object Model
 An object model contains classes. Classes define the structure
and behavior of a set of objects, sometimes called objects
instances. The structure is represented as attributes (data
values) and associations (relationships between classes).
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The Persistence Frameworks
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7.3 Persistence Frameworks
 The Purpose of a Persistence Framework
 Hibernate
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The Purpose of a Persistence Framework
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Hibernate
 Object / Relational mapping (ORM) and persistence
/ query framework
 i.e. It does even more stuff for you!
 Some features of Hibernate
 HibernateDaoSupport – superclass, easy HibernateTemplate access
 Database independence - sits between the database and your java code,
easy database switch without changing any code
 Object / Relational Mapping (ORM) - Allows a developer to treat a
database like a collection of Java objects
 Object oriented query language (HQL) - *Portable* query language,
supports polymorphic queries etc.
 You can also still issue native SQL, and also queries by “Criteria”
(specified using “parse tree” of Java objects)
 Hibernate Mapping - Uses HBM XML files to map value objects (POJOs)
to database tables
 Transparent persistence - Allows easy saves/delete/retrieve for simple
value objects
 Very high performance “in general” due to intelligent (2-level) caching,
although in a few cases hand-written SQL might beat it
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Hibernate
 Hibernate basically sits between the DB and
your code
 Can map persistent objects to tables
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Database Design
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7.4 Database Design
 Purpose
 Overview
 Steps
 Map persistent design classes to tables
 Distribute class behavior to the database
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Purpose
To ensure that persistent data is stored consistently
and efficiently.
To define behavior that must be implemented in the
database.
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Database Design Overview
Supplementary
Specifications
Use-Case Realization
Database
Design
Data Model
Design
Guidelines
Design Classes
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Steps
Map Persistent Design Classes to the Data Model
Optimize the Data Model for Performance
Optimize Data Access
Define Storage Characteristics
Define Reference Tables
Define Data and Referential Integrity Enforcement Rules
Distribute Class Behavior to the Database
Review the Results
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Mapping Persistent Classes to Tables
 In a relational database
 Every row is regarded as an object
 A column in a table is equivalent to a persistent
attribute of a class
Attributes from object type
Student
- name : String
- address : String
- studentID : Long
Name
Thomas Stuart 123456
Object Instance
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Student_ID
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Mapping Persistent Classes to Tables - Example
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Map Class Behavior to Stored Procedures
 Determine if any operations can be
implemented as a stored procedure
 Candidate operations
 Deal with persistent data
 Any operations where a query is involved in a
computation
 Need to access the database to validate data
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What Are Stored Procedures?
 A stored procedure is executable code
which runs under the RDBMS
 Two types of stored procedures
 Procedures: Executed explicitly by an
application
 Triggers: Invoked implicitly when some
database event occurs
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Example: Map Class Behavior to Stored Procedures
Class
Candidate Operations
• getTuition
Student.
• addSchedule
+ getTuition()
+ addSchedule()
+ getSchedule()
+ deleteSchedule()
+ hasPrerequisites()
# passed()
<<class>> + getNextAvailID()
+ getStudentID()
+ getName()
+ getAddress()
• getSchedule
• deleteSchedule
• getStudentID
• getName
• getAddress
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Example: Map Class Behavior to Stored Procedures
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