Applying UML Diagrams Across Project Phases: From Initiation to System Design

Overview The article demonstrates how to apply suitable UML diagrams at each stage of a software project, focusing on practical usage, capturing user requirements, and translating design intent into clear visual models.

Case Backgrounds Two examples are presented: an electronic procurement system for a large appliance manufacturer and an inpatient/outpatient management system for Xinren Hospital.

1. Project Initiation Stage This phase corresponds to problem definition and feasibility study. Key interview points include project scope, essential business processes, technical constraints, and success factors.

2. Requirements Analysis Stage The goal is to collect and document requirements, producing a specification document. Use case diagrams are highlighted as a primary tool, supported by business process design using activity diagrams and the Eriksson‑Penker Business Extension Model.

Business process design emphasizes goal‑oriented modeling; activity diagrams capture high‑level workflows without detailing files or data.

3. Use‑Case Modeling Steps to identify use cases: (1) derive candidates from activity diagrams via stakeholder interviews, (2) write normal flow descriptions as affirmative sentences, and (3) describe alternative flows and exception handling. Test cases are then derived from the use‑case specifications.

4. System Design Stage The design phase implements the identified use cases using three analysis classes:

Control Objects – encapsulate functional responsibilities of use cases.

Entity Objects – represent core domain concepts and data.

Boundary Objects – interface with external actors or systems.

Control objects are modeled with class diagrams and refined with two‑stage sequence diagrams (black‑box then detailed).

Entity objects are identified via Peter Coad’s transaction pattern, forming the basis for domain models and class diagrams.

5. Interaction Modeling Sequence diagrams illustrate object collaborations for each use case; communication diagrams validate the consistency of sequence diagrams with the domain model. Interaction overview diagrams combine multiple interaction diagrams using activity diagram notation.

6. Detailed Design Artifacts Object diagrams provide snapshots of system state at specific moments, while state‑machine diagrams capture lifecycle transitions of key entities (e.g., hospital beds). Time diagrams highlight temporal constraints such as automatic state changes after a timeout.

Conclusion The article covers the main UML diagrams used in requirements analysis and system design, noting that additional UML diagram types exist but are not detailed here.