Martin Fowler is a British software developer, author and international public speaker on software development, specialising in object-oriented analysis and design, UML, patterns, and agile software development methodologies, including extreme programming.
Design Patterns: Elements of Reusable Object-Oriented Software (1994) is a software engineering book describing software design patterns. The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword by Grady Booch. The book is divided into two parts, with the first two chapters exploring the capabilities and pitfalls of object-oriented programming, and the remaining chapters describing 23 classic software design patterns. The book includes examples in C++ and Smalltalk.
The facade pattern is a software-design pattern commonly used in object-oriented programming. Analogous to a facade in architecture, a facade is an object that serves as a front-facing interface masking more complex underlying or structural code. A facade can:
The Law of Demeter (LoD) or principle of least knowledge is a design guideline for developing software, particularly object-oriented programs. In its general form, the LoD is a specific case of loose coupling. The guideline was proposed by Ian Holland at Northeastern University towards the end of 1987, and the following three recommendations serve as a succinct summary:
In software development, code reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software, following the reusability principles.
In software engineering, coupling is the degree of interdependence between software modules; a measure of how closely connected two routines or modules are; the strength of the relationships between modules.
In computing and systems design, a loosely coupled system is one
- in which components are weakly associated with each other, and thus changes in one component least affect existence or performance of another component.
- in which each of its components has, or makes use of, little or no knowledge of the definitions of other separate components. Subareas include the coupling of classes, interfaces, data, and services. Loose coupling is the opposite of tight coupling.
In object-oriented design, the dependency inversion principle is a specific methodology for loosely coupled software modules. When following this principle, the conventional dependency relationships established from high-level, policy-setting modules to low-level, dependency modules are reversed, thus rendering high-level modules independent of the low-level module implementation details. The principle states:
Glossary of Unified Modeling Language (UML) terms provides a compilation of terminology used in all versions of UML, along with their definitions. Any notable distinctions that may exist between versions are noted with the individual entry it applies to.
Efferent coupling is a coupling metric in software development. It measures the number of data types a class knows about.
Object-oriented design (OOD) is the process of planning a system of interacting objects for the purpose of solving a software problem. It is one approach to software design.
In software engineering, SOLID is a mnemonic acronym for five design principles intended to make object-oriented designs more understandable, flexible, and maintainable. The principles are a subset of many principles promoted by American software engineer and instructor Robert C. Martin, first introduced in his 2000 paper Design Principles and Design Patterns discussing software rot.
NDepend is a static analysis tool for .NET managed code. The tool proposes a large number features, from dependency visualization to Quality Gates and Smart Technical Debt Estimation. For that reasons the community refers to it as the "Swiss Army Knife" for .NET Developers.
In the field of software engineering, the interface segregation principle (ISP) states that no code should be forced to depend on methods it does not use. ISP splits interfaces that are very large into smaller and more specific ones so that clients will only have to know about the methods that are of interest to them. Such shrunken interfaces are also called role interfaces. ISP is intended to keep a system decoupled and thus easier to refactor, change, and redeploy. ISP is one of the five SOLID principles of object-oriented design, similar to the High Cohesion Principle of GRASP. Beyond object-oriented design, ISP is also a key principle in the design of distributed systems in general and microservices in particular. ISP is one of the six IDEALS principles for microservice design.
In computer programming, package principles are a way of organizing classes in larger systems to make them more organized and manageable. They aid in understanding which classes should go into which packages and how these packages should relate with one another. Package principles also includes software package metrics, which help to quantify the dependency structure, giving different and/or more precise insights into the overall structure of classes and packages.
JArchitect is a static analysis tool for Java code. This tool supports a large number of code metrics, allows for visualization of dependencies using directed graphs and dependency matrix. The tools also performs code base snapshots comparison, and validation of architectural and quality rules. User-defined rules can be written using LINQ queries. This possibility is named CQLinq. The tool also comes with a large number of predefined CQLinq code rules.
In software engineering, a microservice architecture is a variant of the service-oriented architecture structural style. It is an architectural pattern that arranges an application as a collection of loosely coupled, fine-grained services, communicating through lightweight protocols. One of its goals is that teams can develop and deploy their services independently of others. This is achieved by the reduction of several dependencies in the code base, allowing for developers to evolve their services with limited restrictions from users, and for additional complexity to be hidden from users. As a consequence, organizations are able to develop software with fast growth and size, as well as use off-the-shelf services more easily. Communication requirements are reduced. These benefits come at a cost to maintaining the decoupling. Interfaces need to be designed carefully and treated as a public API. One technique that is used is having multiple interfaces on the same service, or multiple versions of the same service, so as to not disrupt existing users of the code.
In computer programming, design smells are "structures in the design that indicate violation of fundamental design principles and negatively impact design quality". The origin of the term "design smell" can be traced to the term "code smell" which was featured in the book Refactoring: Improving the Design of Existing Code by Martin Fowler.
CppDepend is a static analysis tool for C/C++ code. This tool supports a large number of code metrics, allows for visualization of dependencies using directed graphs and dependency matrix. The tools also performs code base snapshots comparison, and validation of architectural and quality rules. User-defined rules can be written using LINQ queries. This possibility is named CQLinq. The tool also comes with a large number of predefined CQLinq code rules.
The entity-control-boundary (ECB), or entity-boundary-control (EBC), or boundary-control-entity (BCE) is an architectural pattern used in use-case driven object-oriented software design that structures the classes composing a software according to their responsibilities in the use-case realization.
