CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Overview of Object-Oriented Design
Highlights of OOD Concepts,
Components, and Process
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
SD vs. OOD - 1
Responsibilities
Design
Component
design
interface
design
Message
Design
architectural
design
Class/Object Design
data
design
Subsystem Design
Design Patterns (domain Objects)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
SD vs. OOD - 2
- With OO development, think objects (data and operations)
rather than functional procedures (during analysis and
design).
- OOD focuses more on the collaboration among objects than
data flow between components of the system.
- OOD exhibits different levels of modularity (subsystem
modules to method).
- With OOD, system architecture has more to do with object
collaboration than with control flow (as in SD).
- OOD methods provide better support for essential design
concepts - abstraction, modularity, functional independence,
information hiding, and reuse.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
OOA and OOD
OO Analysis
OO Design
Implementation
OO Testing
Deployment
Class
Modeling
Object
Relationship
Modeling
Object
Behavior
Modeling
OO Analysis
OO Design
Implementation
OO Testing
Deployment
Sub-System
Design
Message
Design
Class
Design
Responsibilities
Design
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Mapping OOA and OOD
Attributes
Operations
Collaborators
Class
Model
Object
Relationships
Use
Cases
Responsibilities
Design
Message
Design
Class/Object Design
Object
Behavior
Model
Subsystem Design
Design Patterns
(domain Objects)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
OOA and OOD Terminology
Another mapping view:
Analysis Model
Classes
Design Model
Objects
Attributes
Data Structures
Methods
Algorithms
Relationships
Messaging
Behavior
Control
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
OOD Layers - 1
- Design Patterns: Deals with reusable designs (domain
objects).
(repeated (reusable) classes and objects that found to solve
specific design problems, e.g., user login and authentication,
integrated circuit, car air-condition system, shopping cart,
etc…)
- Subsystem Design: Deals with subsystems that form the
overall system architecture.
(detailed design of self-contained and highly-independent
groups of classes that define specific requirements (major
functions of the system))
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
OOD Layers - 2
- Class/Object Design: Deals with relationships among classes
that define each subsystem.
(detailed design of inheritance hierarchies for subsystems)
- Message Design: Deals with internal and external interface
design.
(detailed design of messages exchanged among objects and
interactions between system objects and external entities)
- Responsibilities Design: Deals with data structures and
algorithm design.
(internal detailed design of each class - its attributes and
operations)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
OOD Methods
OOD methods vary in their processes, presentation forms
(diagrams), notations, and terminologies. However, they all
produce similar results.
A design method must support building modular architectures
with fewer interfaces, small interfaces (less data passed
around), and explicit interfaces (well-defined interfaces), and
information hiding.
Examples: -
Booch method
Rumbaugh method
Jacobson method
Coad/Yourdon method
Wirfs/Brock method
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Generic Steps of OOD
1. Identify subsystems and allocate to processors and tasks
2. Design data management, interface support, and task
management
3. Design system control mechanism
4. Perform object design (operations and data structures)
5. Perform message design (collaboration among objects)
6. Create message model (behavior modeling)
7. Review the design and refine as needed (iterative process)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Unified Approach to OOD
Responsibilities
Design
OOD Process
Object
Design
System
Design
Message
Design
Class/Object Design
Subsystem Design
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
System Design Process
Activities of system design process:
Step 1. Partition the analysis model into subsystems.
Step 2. Identify concurrency (dictated by the problem) and
allocate subsystems to processors and tasks.
Step 3. Design an appropriate control mechanism for task
management.
Step 4. Develop a design for the user interface.
Step 5. Choose a basic strategy for implementing data
management.
Step 6. Identify global resources and the control mechanisms
required to access them.
Step 7. Consider how boundary conditions should be handled
(intersubsystem communications).
Step 8. Review the design and consider trade-offs.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 1: Partition the Analysis Model - 1
Identify potential subsystems (self-contained and highly
independent groups of classes that define specific functions)
How?
A subsystem
- has a well-define interface (check use-cases)
- has reasonable number of classes
- has classes that communicate with each others only (not
with outside classes) (check object behaviour diagram)
- may include internal subsystems (check use-cases)
Note: Layering design of subsystems may be required (e.g., GUI
layer, computing subsystems(s) layer, data management
layer).
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 1: Partition the Analysis Model - 2
UML Class Diagram:
During OOA, create conceptual class diagrams
- focus on classes that are apparent in the problem statement
and of interest to the customer.
- don’t worry about classes needed to implement the system
During OOD, create specification class diagrams
- add classes and relationships needed for modeling the
solution (classes of interest to the developer)
- add more details into individual classes (attributes and
operations)
- identify subsystems and use package notation.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 1: Partition the Analysis Model - 3
Class diagrams:
- used to document classes and show static structure of
classes/subsystems.
- don’t show how classes interact (messages). Collaboration
and sequence diagrams show that (dynamic view).
- describe association, generalization, and aggregation
relationships among classes.
- show class details (attributes and operations).
- show class interface.
- show individual object instances within the class structure.
- used throughout the development cycle.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 2: Identify Concurrency & Tasks
Class (subsystems) that are active at the same time (act on the
same events synchronously) are considered concurrent.
How?
- check object behavior diagram (state machine or activity
diagram) for parallel threads of control (i.e., an object sends a
message to another and continues processing)
- consider each control thread as a task
- allocate tasks to HW processors considering performance
requirements (or same processor using OS mutli-threading
capability)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 3: Task Management Objects
Task initiation and management are modeled by control objects.
How?
- determine task characteristics such as its initiation (event- or
clock-driven), priority for resources, and criticality (should
continue to operate with low resources).
- define control object (attributes/operations) required to
coordinate the task with others.
(Task name, description, priority, services (object operations),
coordinated by (invoked by), input/output).
- show task control object on the object collaboration (behavior)
diagrams.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 4: User Interface Design
User interface is often modeled as a subsystem.
How?
- check use-cases to identify system users (actors)
- from use-cases, derive command hierarchy to define menu
components for each actor and its usage scenario.
- Refine the command hierarchy until all uses-cases can be
navigated via the command hierarchy.
- Note that most interface classes are reused from libraries or
system environment.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 5: Data Management
Data management is accomplished by attributes and operations
defined to manipulate, store, and retrieve data objects (from
system database)
How?
- include such attributes and operations within classes that
manipulate data objects.
- or, design special class(es) to host such attributes and
operations (i.e., to save and load data objects as needed by
the system).
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 6: Resource Management
Subsystems may compete for resources (HW and data
resources). Resource allocation control may be a required
part of the design.
Often, resource management is performed by the OS and
DBMS.
How?
- If resources are part of the application, the designer my define
an object (guardian or gatekeeper object) for each resource to
coordinate access to that resource.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 7: Intersubsystem Communications
Collaboration between subsystems is define by “contracts” or
“subsystem interfaces” and is implemented by message(s)
among the subsystems.
How?
- for each contract (interaction), define its type, collaborating
subsystems(s), classes(s) within the subsystem(s),
operation(s) within the class(es), and the message format.
- show collaborations (messages) on subsystem collaboration
diagrams.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Object Design Process
Object design process is focused on providing detailed design of
the objects (attributes and methods) and their messages.
Component-level design principles (Ch-11, textbook) are
application to object design.
Activities of object design process:
1 - Object description (message design)
2 - Algorithm design
3 - Data structure design
Program Design Language (PDL) is used to express object
design (PDLs come in different flavors).
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 1: Object Description
Object description includes protocol (interface) description and
implementation description.
Protocol description is a listing all message that the object can
respond to (services it provides). This is important for clients
(users) of the object.
Implementation description provides internal (hidden) details of
operations that implement the protocol.
PDL is used to express object description (protocol and
implementation).
Messages may be organized in categories (e.g., for SafeHome
system: configuration, event, monitoring).
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 2: Algorithm Design
Each operations of the class is expressed as an algorithm and is
implemented as a self-contained module.
A complex operation may be divided into separate operations,
such that each operation performs a well-defined task.
Stepwise refinement may be applied:
- define operation interfaces (list of parameters if any)
- fill-in operation body sections
- refine body details as needed
Key Points:
The level of details should be sufficient enough so that it can
be translated to target PL syntax without additional help from
the designer (designer’s knowledge of the PL is essential!)
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Step 3: Data Structure Design
Defining data structures is done in conjunctions with operation
design since operation design may require knowledge of data
structures that implement object attributes.
Optimization of objects design (algorithmic and data design)
should be conducted to ensure efficient processing, ease of
implementation, and efficient utilization of resources.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Software Design Documentation
For structured design, IEEE 1016-1993 standard (next slide)
sections 1 through 5 describe the software architecture and
section 6 describes detailed design.
For OOD, section 6 can be replaced with detailed description of
classes (see the following 29)
RUP templates are more appropriate for capturing and expressing
OOD details. Note section names and order may vary among
documents.
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
IEEE 1016-1987 Standard for SDD
Table of Contents
1. Introduction
1.1 Purpose
1.2 Scope
1.3 Definitions, acronyms, and
abbreviations
2. References
3. Decomposition description
3.1 Module decomposition
3.1.1 Module 1 description
3.1.2 Module 2 description
3.2 Concurrent process decomposition
3.2.1 Process 1 description
3.2.2 Process 2 description
3.3 Data decomposition
3.2.1 Data entry 1 description
3.2.2 data entry 2 description
4. Dependency description
4.1 Intermodule dependencies
4.2 Interprocess dependencies
4.3 Data dependencies
5. Interface description
5.1 Module interface
5.1.1 Module 1 description
5.1.2 Module 2 description
5.2 Process interface
5.2.1 Process 1 description
5.2.2 Process 2 description
6. Detailed design
6.1 Module detailed design
6.1.1 Module 1 details
6.1.2 Module 2 details
6.2 Module detailed design
6.2.1 Data entry 1 details
6.2.2 Data entry 2 details
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
RUP Major Sections of OO SDD
Other sections and subsections may be added as needed.
Table of Contents
1. Introduction
1.1 Purpose
1.2 Scope
1.3 Definitions, acronyms, and
abbreviations
1.4 References
2. Glossary
3. Use Cases
4. Design Overview
4.1 Introduction
4.2 System Architecture
4.3 System Interfaces
4.4 Constraints and Assumptions
5. System Object Model (System Design)
5.1 Introduction
5.2 Subsystems
5.3 Subsystem Interfaces
6. Object Descriptions (Object Design)
6.1 Objects in Subsystem 1
6.2 Objects in Subsystem 2
....
6.n Sequence Diagrams
7. Object collaboration (Process View)
7.1 Objects in Subsystem 1
7.2 Objects in Subsystem 2
8. Data design
9. Dynamic Model
9.1 State Diagrams
9.1.1 State Diagram 1
9.1.2 State Diagram 2
10. Non-functional requirements
11. Supplementary Documentation
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
Useful Links
RUP Templates (complete set):
http://jdbv.sourceforge.net/RUP.html
Software Architecture document sample:
http://atlas-connect-forum.web.cern.ch/Atlas-connectforum/SDP/Architecture_guidelines.htm
Software Architecture template sample:
http://atlas-connect-forum.web.cern.ch/Atlas-connect-forum/documents/
ArchitectureDesignTemplate_Word.dot
Useful Links:
http://atlas-connect-forum.web.cern.ch/Atlas-connectforum/documents_page.htm
SDD example:
http://auss.abez.ca/SDD.html
CS 8532: Advanced Software Engineering
Dr. Hisham Haddad
End of Overview