Logical Application component is an encapsulation of application functionality that is independent of a particular implementation. As such, it is a replaceable part of a system. It encapsulates its contents and exposes its functionality through a set of interfaces. An application component performs one or more application functions. It may collaborate with other application components through the application interfaces of those components.

Component-based software engineering (CBSE), also called component-based development (CBD), is a style of software engineering that aims to construct a software system from components that are loosely-coupled and reusable. This emphasizes the separation of concerns among components.[1][2]

To find the right level of component granularity, software architects have to continuously iterate their component designs with developers. Architects need to take into account user requirements, responsibilities and architectural characteristics.[3]


An example of two components in UML: Checkout processes a customer's order, which requires the other one to bill the credit card.

For large-scale systems developed by large teams, a disciplined culture and process is required to achieve the benefits of CBSE.[4] Third-party components are often utilized in large systems.

The system can be designed visually with the Unified Modeling Language (UML). Each component is shown as a rectangle, and an interface is shown as a lollipop to indicate a provided interface and as a socket to indicate consumption of an interface.

Component-based usability testing is for components that interact with the end user.


  1. ^ George T. Heineman, William T. Councill (2001). Component-Based Software Engineering: Putting the Pieces Together. Addison-Wesley Professional, Reading 2001 ISBN 0-201-70485-4
  2. ^ Clemens Szyperski, Dominik Gruntz, Stephan Murer (2002). Component Software: Beyond Object-Oriented Programming. 2nd ed. ACM Press - Pearson Educational, London 2002 ISBN 0-201-74572-0
  3. ^ Fundamentals of Software Architecture: An Engineering Approach. O'Reilly Media. 2020. ISBN 978-1492043454.
  4. ^ Douglas C. Schmidt. "Why Software Reuse has Failed and How to Make It Work for You". Retrieved 14 May 2024.



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