Learn software concepts - Cleanroom software engineering

Cleanroom software engineering is a formal approach to software development that can lead to software that has remarkably high quality. It uses box structure specification (or formal methods) for analysis and design modeling and emphasizes correctness verification, rather than testing, as the primary mechanism for finding and removing errors. Statistical use testing is applied to develop the failure rate information necessary to certify the reliability of delivered software.

The cleanroom approach begins with analysis and design models that use a box structure representation. A "box" encapsulates the system at a specific level of abstraction. Black boxes are used to represent the externally observable behavior of a system. State boxes encapsulate state data and operations. A clear box is used to model the procedural design that is implied by the data and operations of a state box.

Correctness verification is applied once the box structure design is complete. The procedural design for a software component is partitioned into a series of sub-functions. To prove the correctness of the sub-functions, exit conditions are defined for each sub-function and a set of sub-proofs is applied. If each exit is condition is satisfied, the design must be correct.

Once correctness verification is complete, statistical use testing commences. Unlike conventional testing, cleanroom software engineering does not emphasize unit or integration testing. Rather, the software is tested by defining a set of usage scenarios, determining the probability of use for each scenario, and then defining random tests that conform to the probabilities. The error records that result are combined with sampling, component, and certification models to enable mathematical computation of projected reliability for the software component.

The cleanroom philosophy is a rigorous approach to software engineering. It is a software process model that emphasizes mathematical verification of correctness and certification of software reliability. The bottom line is extremely low failure rates that would be difficult or impossible to achieve using less formal methods.

Learn software concepts - Domain Engineering in CBSE process

The CBSE process encompasses two concurrent sub-processes - domain engineering and component based development.
The intent of domain engineering is to identify, construct, catalog, and disseminate a set of software components that have applicability to existing and future software in a particular application domain. The overall goal is to establish mechanisms that enable software engineers to share these components—to reuse them.

The overall approach to domain analysis is often characterized within the context of object-oriented software engineering. The steps in the process are defined as follows:
- Define the domain to be investigated.
- Categorize the items extracted from the domain.
- Collect a representative sample of applications in the domain.
- Analyze each application in the sample and define analysis classes.
- Develop an analysis model for the classes.

Some of the domain characteristics are as follows :
- It is sometimes difficult to determine whether a potentially reusable component is applicable in a particular situation. A set of domain characteristics may be defined to make this determination.
- A domain characteristic is shared by all software within a domain. It defines generic attribute of all products that exist within the domain. E.g., generic characteristics might include: the importance of safety/reliability, programming language, concurrency in processing.

Examples of application domains are:
* Air traffic control systems
* Defense systems
* Financial market systems

Domain engineering begins by identifying the domain to be analyzed. This is achieved by examining existing applications and by consulting experts of the type of application you are aiming to develop. A domain model is then realized by identifying operations and relationships that recur across the domain and therefore being candidates for reuse. This model guides the software engineer to identify and categorize components, which will be subsequently implemented.

One particular approach to domain engineering is Structural Modelling. This is a pattern-based approach that works under the assumption that every application domain has repeating patterns. These patters may be in function, data, or behaviour that have reuse potential.