Systems Design and Measurable Objectives

Systems Design

• Systems design aims to define, organize, and structure the components of the final solution, serving as a blueprint for development.
• Systems analysis is the initial stage, providing input for systems design.
• Systems design focuses on the system's high-level architecture. This includes the hardware and network infrastructure, how sub-systems interact, and standards (e.g., screens, reports).
• Detailed design delves deeper into specifications. It encompasses class design (defining attributes and methods), user interface implementation, business logic, sequence design (guiding software methods), UI and report design, database design, and security/control design.

Measurable Objectives in Design

• Objectives should be quantifiable and testable, aligning with SMART criteria: Specific, Measurable, Actionable, Realistic, and Time-Based.
• Specific objectives are clear and unambiguous. For instance, instead of "more visitors," aim for a specific numerical target or percentage increase.
• Measurable objectives are quantifiable for tracking progress and determining success. For example, "decrease user sick leave by 20%".
• Actionable objectives are achievable through concrete solutions, like increasing user engagement using design elements such as upvote buttons, feedback forms, or comments.
• Realistic objectives are attainable within constraints; for example, aiming for every visitor to signup can be overly ambitious and needs adjustment.
• Time-based objectives have clear timelines; for example, acquiring 1,000 users monthly over six months.

Qualities of Design

• Functional: The system should perform all stated functions.
• Efficient: Minimizes time and resources (like disk space) while performing functions efficiently.
• Economical: Consideration of both initial setup and ongoing costs (Total Cost of Ownership).
• Reliable: Resistant to hardware and software failures, ensuring data integrity.
• Secure: Safeguards against unauthorized access and malicious attacks (like passwords and firewalls).
• Flexible: Adaptable to evolving needs and user settings.
• Buildable: Design should be clear and manageable for programmers.
• Manageable: System should be easy for managers to estimate workload and sub-system completion.
• Maintainable: Effort for system maintenance is minimized.
• Usable: Provides a productive user experience.
• Reusable: Incorporates reusable components and design patterns for flexibility and extension..
• Elegant-Beautiful: A visually appealing design helps encourage user engagement.

What is a System?

• A System is a collection of connected components that accomplish a specific function, like the respiratory or digestive systems. It serves as a blueprint for the design, building, and deployment of related systems..

What is Architecture?

• Architecture refers to how the components of a system are organized and how they interact with each other and their environment.

Cloud Services Architecture

• Cloud services are on-demand services accessible over the internet by cloud computing providers.
• Infrastructure as a service (IaaS): Users receive fundamental computing resources (virtual machines, storage, networking) to build their own platforms and applications.
• Platform as a service (PaaS): Provides a pre-configured platform for developing, deploying, and managing applications, allowing users to focus on app development without managing the underlying infrastructure.
• Software as a service (SaaS): Delivers ready-to-use software and applications on cloud infrastructure.
• Backend as a service (BaaS): Provides cloud-based backend services (data storage, user authentication).
• Function as a service (FaaS): Allows developers to deploy and run individual functions or code pieces in the cloud.

Client/Server Architecture

• Divides an application into client (user interface) and server (powerful computer) components.
• The client sends requests; the server processes them, manages storage, and sends responses to the client.

Three-Layer Architecture

• Divides an application into view (user interface), logic (business logic), and data (data access) layers.

Application Programming Interface (API)

• An API acts as an intermediary between software components or systems.
• It defines how components interact (e.g., retrieving data, creating objects).
• Uses standardized data formats (e.g., JSON, XML) to ensure compatibility between different applications.
• Includes web protocols like HTTP and HTTPS for secure communication between client and server.

Object-Oriented Design

• Object-Oriented Design (OOD) is a software development approach.
• Classes act as blueprints or templates for creating objects.
• Classes define structure and behavior of objects.
• Objects represent entities within the system (possessing attributes and methods).
• Design Class Diagram (DCD): Visual representation of objects, outlining their attributes and methods.

GRASP

• GRASP (General Responsibility Assignment Software Patterns) is a set of nine principles that help in assigning responsibilities to objects. These principles work towards making systems more maintainable and understandable.

Low Coupling

• Low coupling refers to the minimization of interdependencies between different classes/objects within a system.
• Minimize the impact of any change in a class on other classes within the system. Reusability is enhanced, and the effect of changes can be localized.

High Cohesion

• High cohesion works toward keeping classes focused on a single task or responsibility.
• Complex systems becomes more manageable and maintainable.

Polymorphism

• Polymorphism is a concept in object-oriented programming,allowing multiple methods with the same name but with different parameters (static/method overloading) or based on different object types after inheriting from a common class/base class (dynamic/method overriding or static and dynamic binding) to perform different tasks through single method definition.

Databases

• Database management systems (DBMS) are sets of programs that help organize, store, and retrieve data.
• Layered architecture for databases comprises a presentation layer (showing data to users), application logic layer (handling business logic, and domain layer (holding business logic info and rules).
• Data providers (ex. Connection), data objects, and data adapters are integral elements that work with a database to get and update data.

Collections

• When dealing with groups of items (objects), better approaches than arrays can be used to organize them (collections). Collections provide methods for managing and accessing groups of objects, like search, navigation, and removing items.