--- title: "Deployment diagram as class diagram of nodes" subject: "Object Oriented Analysis and Design" chapter: 3 key: "semester_6/object_oriented_analysis_and_design:deployment-diagram-special-class-diagram" source: https://www.bctengineer.com/q/semester_6/object_oriented_analysis_and_design/deployment-diagram-special-class-diagram site: BCT Engineering --- # Deployment diagram as class diagram of nodes Object Oriented Analysis and Design · Chapter 3: Object Oriented Design - Asked in: 2072 Asoj, 5 marks - Video: [UML 2 Deployment Diagrams](https://www.youtube.com/watch?v=nTtQwGoUUNc) — Derek Banas - Answer checked by Claude Sonnet 5.5 on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/object_oriented_analysis_and_design/deployment-diagram-special-class-diagram - Whole chapter: https://www.bctengineer.com/md/semester_6/object_oriented_analysis_and_design/chapter-3 ## Question In many ways, a deployment diagram is just a special kind of class diagram, which focuses on a system's nodes. Justify this statement. ## Short answer A deployment diagram is a special class diagram where nodes (hardware/execution environments) act as classifiers with attributes, operations, instances, and relationships (associations, dependencies, generalization). It uses same notation (rectangles, stereotypes, multiplicities) but focuses on physical runtime mapping of artifacts to nodes and communication paths instead of logical software classes. ## Answer A **deployment diagram** shows the physical architecture of a system at run time: the **nodes** (hardware devices or execution environments), the **artifacts** (executables, libraries, files, databases) that are deployed on them, and the **communication paths** between nodes. #### Why it is a special kind of class diagram 1. **Nodes are classifiers.** Like classes, nodes have a name, can have attributes (memory, processor speed) and operations/services, and can be instantiated: "node type" and "node instance" parallel "class" and "object". 2. **Same kind of relationships.** Nodes are connected with **associations** (communication paths such as `<>`), with multiplicity, and can be related by dependency, aggregation (a node containing nodes) and generalization (a `Server` node specialised into `WebServer`, `DBServer`). 3. **Same notation rules.** Rectangles (3D boxes), stereotypes `<>`, `<>`, names, compartments, multiplicities, and notes are used just as in a class diagram. 4. **Focus is changed.** Instead of the logical classes of the software, the focus is on the physical elements of the system: the nodes on which components run. ```text +------------------+ +-------------------+ /| <> /| TCP/IP | <> /| / | Client PC / |---------| Application Srv / | +--+---------------+ | 1 * +-----------------+ | | browser | | | order.war | | +------------------+--+ +--------+--------+-+ | JDBC +-------+---------+ | <> DB | | orders.mdb | +-----------------+ ``` Hence a deployment diagram is a class diagram whose "classes" are nodes, with associations between nodes, and with artifacts placed inside them, to show how software is mapped to hardware. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why are nodes similar to classes? A. Nodes cannot have attributes B. Nodes are always software C. Nodes have no names D. Nodes have names, attributes and operations and have types and instances Answer: D. Like classes, nodes are classifiers with attributes and operations, and have types and instances. (Key point: Nodes as classifiers) 2. Which relationships can connect nodes like classes? A. Associations with multiplicity, dependency, aggregation and generalization B. Only message arrows C. Only use-case links D. None Answer: A. Nodes use associations (communication paths), dependency, aggregation and generalization, as classes do. (Key point: Relationships among nodes) 3. What differs in a deployment diagram compared with a class diagram? A. It shows logical classes only B. It focuses on physical nodes and the artifacts deployed on them C. It has no notation rules D. It shows message order Answer: B. The focus shifts from logical classes to the physical nodes where software runs. 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