Software Development and Systems Design

Systems Design Activities

• Defining the system architecture: The architect decides on the technical architecture for the system. For example, they might choose to build a web application with a cloud-based database.
• Detailed design of components: Every part of the system is designed in detail, including forms, tables, and automatic alerts.
• Designing the database: A database is created to store all of the relevant data. The database design will include tables, table relationships, and rules for data entry.
• User Interface (UI) design: The designer creates mockups of how the screens will look for the user to make sure that the system is intuitive and easy to use.

The Software Development Process

• Understand the need: This is where developers identify the business need for the system.
• Capture the vision: The vision for the system is developed.
• Define a solution: A solution is developed to directly address the need.
• Communicate the vision and solution: The vision and solution are communicated with the stakeholders.
• Build the solution: Developers build the solution based on the design.
• Confirm that the solution meets the need: The system is tested to make sure that it meets the needs.
• Launch the solution system: The system is made available to the users.

The System Development Life Cycle (SDLC)

• The SDLC is the complete process for building, launching, and maintaining an information system.
• It includes six core processes:
  • Identify the problem or need and obtain approval.
  • Plan and monitor the project.
  • Discover and understand the details of the problem or need.
  • Design the system components that solve the problem.
  • Build, test, and integrate system components.
  • Complete system tests and then deploy the solution.
• Project: A project is a planned undertaking with a defined beginning and end that is intended to produce a specific result.

System Development Process

• System Development Process is the actual approach used to develop a particular information system.
• Most development processes now use Agile and Iterative development.
• Agile Development: Uses small, functional increments to deliver the system. This allows for flexibility and frequent feedback.

System Analysis Activities

• Gather Detailed Information: This involves the use of several techniques including interviews, questionnaires, reviewing documents, observing business processes, research, and collecting comments.
• Define Requirements: Developers model the system's functional requirements and define non-functional requirements.
• Prioritize Requirements: Requirements are categorized according to their importance: Essential, important, and nice-to-have.
• Develop User-Interface Dialogs: The flow of interaction between the user and the system is designed.
• Evaluate Requirements with Users: Engage with users to get feedback and adapt requirements.

Information Gathering Techniques

• Several techniques can be used to gather information about a system.
• Interviews
• Questionnaires
• Reviewing documents
• Observing business processes
• Researching vendors
• Collecting comments and suggestions

Reasons for Modeling

• Learning from the Modeling Process: Models can be used to gain insights and understanding.
• Reducing Complexity by Abstraction: Models can simplify complex systems.
• Remembering All the Details: Models can help to ensure that all aspects of the system are documented.
• Communicating with Development Team Members: Models help to facilitate clear communication and collaboration.
• Communicating with Users and Stakeholders: Models can be used to ensure that users and stakeholders understand the system.
• Documenting for Future Maintenance/Enhancement: Models provide a useful reference for future updates and maintenance.

Use Cases

• Definition: A use case is an activity that the system performs, often in response to a request from a user.
• Purpose: Use cases are used to define the functional requirements for a system.
• Decomposition: Analysts break down the system into a set of smaller use cases.
• Techniques for Identifying Use Cases:
  • User Goal Technique
  • Event Decomposition Technique
• Naming Convention: Use cases are named using a verb-noun format.

User Goal Technique Steps

• Identify Potential Users: The first step is to identify all users.
• Classify Users by Functional Role: Users are grouped according to the roles they play in the system.
• Classify Users by Organizational Level: Users are further categorized based on their organizational level.
• Interview Users: Each type of user is interviewed to gather information on their goals for the system.
• Create Preliminary Use Cases: A preliminary list of use cases is created.
• Resolve Duplicates and Inconsistencies: Resolve any issues with the use case names.
• Identify Shared Use Cases: Determine which use cases are shared between different users.
• Review with Users and Stakeholders: The list of use cases is reviewed with users and stakeholders.

Use Case Diagrams

• Definition: A Use Case Diagram is used to visually represent use cases and how they relate to actors.
• Unified Modeling Language (UML): UML is a standardized modeling language used for designing information systems.
• Actor: An actor represents an end user or another system that interacts with the system.
• Primary Actors: Primary actors initiate the use cases, interacting with the system directly to achieve goals.
• System Boundary: This indicates the limits of the application, highlighting what is part of the system versus what is external to it.
• Automation Boundary: The Automation Boundary shows the separation between computerized parts of the system and the user interactions.

Event Decomposition Technique (EDT)

• Identify Events:
  • External Events: Occurs outside the system, initiated by an external actor.
  • Temporal Events: Triggered by reaching a specific time.
  • State Events: Triggered by changes within the system or its internal state.
• Naming Use Cases: Each event is assigned a corresponding use case that describes the response of the system to that event.

Benefits of EDT

• Broader Event Capture: Includes temporal and state events, not just user goals.
• Right-Level Decomposition: Helps break down processes into EBPs, which are basic, single-person tasks done in response to an event.
• Perfect Technology Assumption: Focuses on core functions rather than system controls or error handling.

Temporal Events (Examples)

• Automatically finalize class lists on a specific date to prevent further enrollment.
• Automatically generate a monthly report.

State Events (Examples)

• When a course section is full and the waitlist reaches 20 students, automatically create a new course section.
• When the inventory level falls below the reorder point, automatically reorder inventory.

Modified Use Case Model (Example)

• Student:
  • Display Scheduled Course Sections
  • Enroll in Course Section
  • Waitlist for Course Section
  • Display Timetable
  • Drop Course Section
  • Cancel Waitlist
• System:
  • Finalize Class Lists
  • Open New Course Section

Generalization – Use Case

• A Generalization relation is used to indicate that a specialized use case is a specific way to achieve the goals described by a general use case.
• The open arrowhead points at the more general use case.

Generalization - Actors

• A Generalization link can also be drawn between actors, to indicate a specialization relationship.