Systems Analysis and Design Study Notes

Information Technology (IT) combines hardware, software, data, processes, and people to manage, communicate, and share information.
Systems analysis and design is a step-by-step process for developing high-quality information systems that support business goals.
Systems analysts transform business requirements into IT projects, acting as communicators between users, managers, and programmers.
Business information systems include Enterprise Resource Planning (ERP), Transaction Processing (TP) systems, Business Support Systems, Knowledge Management Systems, User Productivity Systems, Digital Assistants, and Systems Integration.

Strategic planning identifies long-term organizational goals using mission statements, critical success factors, and SWOT analysis (Strengths, Weaknesses, Opportunities, Threats).
Systems requests initiate projects to address business needs such as stronger controls, reduced costs, more information, better performance, improved customer service, or support for new products and services.
Feasibility studies evaluate systems requests using four criteria: operational, economic, technical, and schedule feasibility.
Preliminary investigations evaluate project requests, define project scope and constraints, perform fact-finding, and recommend a course of action.
Project management uses Work Breakdown Structures (WBS), Gantt charts, and PERT/CPM charts to plan, schedule, monitor, and report on project cost, scope, and time.
Expected task duration is calculated using a weighted formula: $\text{Expected Duration} = \frac{B + 4P + W}{6}$

Requirements engineering gathers, represents, validates, and verifies functional requirements (system services) and non-functional requirements (system constraints).
Fact-finding techniques include interviews, document review, observation, questionnaires/surveys, brainstorming, sampling, and research.
Team-based methodologies include Joint Application Development (JAD), Rapid Application Development (RAD), and Agile methods (such as Scrum and Extreme Programming).
Modeling techniques include Functional Decomposition Diagrams (FDDs), Business Process Modeling Notation (BPMN), Data Flow Diagrams (DFDs), and Unified Modeling Language (UML) diagrams.
Data dictionaries serve as central repositories for all data elements, data flows, data stores, processes, entities, and records.

User interface (UI) design focuses on human-computer interaction (HCI), user-centered design, usability, input validation rules, and effective source document and screen layout.
Data design utilizes Relational Database Management Systems (DBMS) to organize data into normalized tables (1NF, 2NF, 3NF) linked by primary, foreign, and candidate keys while enforcing referential integrity.
Entity-Relationship Diagrams (ERDs) depict logical relationships and cardinality (1:1, 1:M, M:N) between system entities.
System architecture defines the physical system blueprint, including client/server architecture (two-tier, three-tier/n-tier), web-based and cloud computing architectures, and network topologies (bus, star, ring, mesh, hierarchical).

Application development translates system designs into code modules using structured analysis, object-oriented development, or agile development methods.
Quality assurance relies on software engineering principles, Capability Maturity Model Integration (CMMI), and ISO standards (such as ISO 9000-3:2014).
Testing follows a sequence of unit testing (including desk checking and stub testing), integration testing, and system/acceptance testing.
Documentation includes program, system, operations, and user documentation.
Installation tasks include setting up separate test and operational environments, data conversion, user training, and system changeover (direct cutover, parallel operation, pilot operation, or phased operation).

User support encompasses help desks, ongoing training, and technical assistance.
System maintenance consists of four categories: corrective (fixing errors), adaptive (adding enhancements), perfective (improving efficiency), and preventive (avoiding future failures).
System security protects information using the CIA triangle (Confidentiality, Integrity, Availability) across six levels: physical, network, application, file, user, and procedural security.
Risk management involves risk identification, risk assessment, and risk control strategies (avoidance, mitigation, transference, acceptance).
Backup and business continuity strategies include full, differential, incremental, or continuous backups, along with disaster recovery plans and hot sites.
System retirement occurs when an information system reaches the end of its economically useful life.