Component Diagram

Welcome to my series of articles on Unified Modeling Language. This is "Session 6 – Component Diagram" of the series. Please view my other documents where I have covered each UML diagram with examples

1. 1







Session


Component Diagram


Checklist
 Introduction to Component Diagram
 Elements of Component Diagram
 Construct Component Diagram for
Case Study

2. 2


Component Diagram



Physical implementation of a system should address three primarily problems, they are
Software, Hardware and the interaction between them. Component Diagram are used to
represent physical implementation of the software design whereas physical architecture of the
system is represented using deployment diagrams. Combine them both you can see your
application software running across your hardware. Session 7 details about Deployment
Diagrams.
Consider each component as a bunch of code running on a physical piece of hardware. Each
component should provide interfaces to be serviced by other components of the software
design. The logical implementation are done by the classes that are encapsulated within the
component.
Components can be grouped into three categories
 Deployment Components – Components which are required to run a system
 Work product Components – Components which produce Deployment components
 Execution Components – Components created while running the application.

Elements of Component diagrams?
Elements of component diagram are not much different than what we have seen in class
diagram and composite structure diagram. UML 2 has a notation to represent component
diagram as shown in the figure below. Just Add () to a class or <<component>> stereotype to a
class.

3. 3


Figure 1: Component Notation
Component Stereotype
Components stereotype provides visual cues about roles played by components in a system.
Some of component stereotype are as follows.

Figure 2: Component Stereotype

Constructing Component Diagram for our Case Study
Problem Statement
We are going to use Coffee Vending Machine for our case study. This is the coffee machine that
are used in coffee shops that are operated by store’s worker. Operator can select the type of
coffee and our system provides one by mixing correct portions of milk, water and flavor.
Operator can cancel the order at any time and the system would stop preparing coffee. Our
system gives status information to the operator too. Figure below shows the component
diagram of Coffee Vending Machine.

4. 4

Solution
Our system has two layers; Application Layer and Middleware Layer. Let us look at the
components and the functionality they provide for the system.
Table 1: Component Diagram Functionalities
Components Functionality
Application Layer

UI

Handles what to be displayed on the screen. It is an executable. It requires
services from Process Order and State Machine to update the display
accordingly


Process Order

Core functionality of coffee making part is handled here. It is an
executable. It updates the state machine and talks with lower layers of the
system to prepare coffee.


State Machine

Maintains the state of the system. Gets input from status manager for
status change events from hardware or from the operator

Middleware Layer

Status Manager

Status Manager uses IPC mechanism and stands a medium of
communication between Application layer and Middleware layer. It
interacts with Interrupt Handler and Tank Manager.


Interrupt Handler

Handles external interrupts to the system. For Example when system losses
it power or when the operator cancels the order. When such events occur
Interrupt Handler informs the status manager so that application layer
components knows about the event.


Tank Manager

It communicates with library files to update the status manager about our
Vending machines tank status.

For Example: If Water tank is empty WaterTank.a presents event
notification to TankManager. TankManager then validates the event and
updates the StatusManager

5. 5


Figure 3: Component Diagram (Case Study)

6. 6







Review

 Component Diagram is used to represent physical implementation
of a software design
 Components can be grouped as Deployment Component, Work
Product Component and Execution Component
 Component states provide visual cue to the function of the component