What is Parnas Table?
A Parnas Table is a tool used in software engineering to manage and document the dependencies between different components or modules in a software system. It is named after David Parnas, a prominent computer scientist known for his work in modular design and software engineering principles.
Purpose:
The Parnas Table helps in understanding and managing the modularization of software by identifying and documenting the dependencies between various modules. It aids in ensuring that changes in one module have minimal impact on others, promoting better software design and maintainability.
Structure:
A Parnas Table typically consists of:
- Modules: List of components or modules in the system.
- Dependencies: Relationships or dependencies between the modules.
- Interfaces: Information about the interfaces or APIs through which modules interact.
- Changes: Tracking of potential impacts or required changes when modifying a module.
Example:
Consider a software system with the following modules: A, B, C, and D. The Parnas Table for these modules might look like this:
Explanation:
- Module A depends on Module B, using specific functions (
X,Y), and provides data or services to Module C. - Module B depends on Module C, using certain functions (
M,N), and provides an API to Module D. - Module C does not depend on any other modules but provides data to Module A.
- Module D does not depend on any other modules and does not provide services to any other modules.
Benefits:
- Clarity: Helps visualize the dependencies and interactions between modules.
- Maintainability: Assists in understanding the impact of changes in one module on others, making it easier to manage and implement changes.
- Modular Design: Encourages modularization by clearly defining interfaces and dependencies.
Usage:
Parnas Tables are particularly useful during the design phase of a project to ensure that modules are properly separated and dependencies are well-managed. They can also be used during code reviews and maintenance to track changes and their impacts.
In summary, a Parnas Table is a valuable tool for managing software modularity and dependencies, helping to create a well-structured and maintainable software system.
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