Software Engineering: SDLC and Object Diagrams

Lecture 01: Introduction & Object Diagram

• Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software.
• Software Engineering(SIE) is defined as a process of analyzing user requirements, designing, building, and testing software applications to satisfy those requirements.
• SDLC (Software Development Life Cycle) is a framework defining the phases/stages throughout the software development process.
• SDLC phases:
  • Requirement Gathering And Analysis
  • Design
  • Implementation
  • Testing
  • Maintenance/Evolution

The Design Phase

• Software design methods include function-oriented S/W design and object-oriented S/W design.
• Object-oriented design defines objects and their interactions to solve a software problem.
• Design model types include structural and dynamic models.
• Modeling languages serve to express information, knowledge, or systems in a structured and consistent manner.
• UML (Unified Modeling Language)is a general-purpose, developmental modeling language intended to provide a standard way to visualize the design of a system.
• UML Diagram Structure:
  • Behavior Diagrams: Activity, state machine, use case, interaction, communication diagram, interaction overview, sequence, and timing diagrams.
  • Structure Diagrams: Class, composite structure, component, deployment, object, package, and profile diagrams.

Class Diagram Revision

• Classes are found using noun/verb analysis and CRC cards.
• Class Structure:
  • Class name: the class name
  • Class attributes: e.g., +id: String, +name: String
  • Class methods: e.g., +getMaxBook(): int
• Class Relationships:
  • Association
  • Inheritance
  • Dependency
  • Aggregation
  • Composition

Object Diagrams

• An object diagram is a graph of instances, including objects and data values.
• A static object diagram is an instance of a class diagram that shows a snapshot of the detailed state of a system at a point in time.
• Object Notation Types:
  • Named Object: objectname : Classname.
  • Anonymous Object: Classname.
• Object with Attributes:
  • objectname: Classname
  • attributename1 ="value"
  • attributename2 ="value"
• "value" is used for string values.

Lecture 02: Interaction Diagrams - Part 1

• An interaction diagram represents an interaction, containing objects and the relationships between them including messages exchanged between the objects.
• Interaction diagrams include Sequence Diagrams (temporal focus) and Communication Diagrams (structural focus).
• Sequence diagrams emphasize the time ordering of messages.
• Elements:
  • Actor
  • Frame
  • Object: objectName: ClassName or :ClassName.
  • Class/Object Stereotypes: Boundary Class, Entity Class, Control Class.
  • Lifelines
  • Execution/Activation Bar

Sequence Diagrams

• Messages:
  • Synchronous Message
  • Asynchronous Message
  • Return Message
  • Participant Creation Message: <>
  • Participant Destruction Message: <>.
• Synchronous Call is used when the sender waits until the receiver has finished processing the message.
• An Asynchronous Call; the sender does not wait for the receiver to finish processing the message and it continues immediately.
• Create and Delete Message
  • Create Message: <>
  • Delete Message: <>
• Lost and Found Message
  • Lost Message
  • Found Message
• Self Calls

Interaction Fragments

• Common interaction fragments include:
• Reference (Ref)
• Alternative (Alt): two or more
• Option (Opt): one
• Iteration (loop)
• Break (break)
• Parallel (par)

Lecture 03: Communication Diagrams

• Communication diagrams emphasize the organization of objects participating in an interaction.
• Symbols:
  • Actor
  • Object
  • Links between Objects
  • Direction of Messages
  • Message sequence numbers e.g., 1, 2, 2.1
  • Frame (interaction frame)
  • Message Syntax E.g., 1.0:login (UN/PW)
  • Self Calls
  • Guard Expressions Syntax: msg sequence no. [Condition] : Msg
• Iteration and Looping Syntax:
  • Msg Sequence No *[Condition]: Msg Signature
  • Msg Sequence No *[condition] [iterative Clause]: Msg Signature (Optional)
• Parallel Activities
  • 2.1 * [Condition]
  • 2.1 * || [Condition] (Concurrently notation)

Rules of Thumb for Diagrams

• Avoid crossing links and crowded diagrams.
• Do not show all interactions.
• Do not model obvious return values.
• Sequence diagrams emphasize the sequences of events well.
• Communication diagrams show the relationships between classes.
• Strengths:
  • Sequence diagrams show sequence or time order.
  • Communication diagrams show flexibility to add new objects in two dimensions.
• Weeknesses:
  • Sequence diagrams are forced to extend to the right when adding new objects.
  • Communication diagrams are difficult to see message sequence.
• Similarities:
  • Semantically equivalent
  • Diagrams can convert from each other without losing most of the information.
  • They model the dynamic aspects of a system.
  • They model the implementation of a use-case scenario.

Lecture 04: State-Chart (State-Machine) Diagram

• State means a particular condition that someone or something is in at a specific time.
• Notations:
  • Composite State
  • Simple State
    • State with Compartment ()
      • Internal Behaviours (entry, exit, do)
        • Internal Behaviours ->Entry, Exit, Do
  • Special States ->Initial State, Final State
• Transitions:
  • Elements: Source State -><Trigger> Target State
  • Trigger: Time Event
  • Call Event/ Change Event
• Self - Transitions: The state in question is exited and entered again
• Types of Triggers
  • Call Event
  • Change Event
  • Time Event
• Call Event/Trigger; Example: buttonPressed()
• Change Event/ Trigger; Example: When (T>100°)
• Time Event/ Trigger; Example: after (1 minute)

State Machine Conditions

• Triggers with Guard Conditions (if true, execute):
  • message() [Guard Condition] / Action
  • when (Condition) [Guard Condition] / Action
  • after (timespan) [Guard Condition] / Action
• Composite states has sub-states that are sequential or concurrent.
• Sub-states are in a separate compartment known as the "Decomposition" compartment.
• Simple Composite State consists of only one region.
• Orthogonal Composite State encompasses more than one region within the decomposition compartment.
• Hidden Decomposition Indicator:
  • entry/-
  • exit/

Lecture 05: Physical Diagrams

• Not much information was given about physical diagrams