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Acyclic Dependencies Principle
The acyclic dependencies principle (ADP) is a software design principle defined by Robert C. Martin that states that "''the dependency graph of packages or components should have no cycles''". This implies that the dependencies form a directed acyclic graph. Example In this UML package diagram, package ''A'' depends on packages ''B'' and ''C''. Package ''B'' in turn depends on package ''D'', which depends on package ''C'', which in turn depends on package ''B''. The latter three dependencies create a cycle, which must be broken in order to adhere to the acyclic dependencies principle. Types of dependencies Software dependencies can either be explicit or implicit. Examples of explicit dependencies includes: * Include statements, such as #include in C/C++, using in C# and import in Java. * Dependencies stated in the build system (e.g. dependency tags in Maven configuration). Examples of implicit dependencies includes: * Relying on specific behaviour that is not well-defined by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directed Acyclic Graph
In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG) is a directed graph with no directed cycles. That is, it consists of vertices and edges (also called ''arcs''), with each edge directed from one vertex to another, such that following those directions will never form a closed loop. A directed graph is a DAG if and only if it can be topologically ordered, by arranging the vertices as a linear ordering that is consistent with all edge directions. DAGs have numerous scientific and computational applications, ranging from biology (evolution, family trees, epidemiology) to information science (citation networks) to computation (scheduling). Directed acyclic graphs are sometimes instead called acyclic directed graphs or acyclic digraphs. Definitions A graph is formed by vertices and by edges connecting pairs of vertices, where the vertices can be any kind of object that is connected in pairs by edges. In the case of a directed graph, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acyclic Dependencies, Circular Dependency Example
Acyclic may refer to: * In chemistry, a compound which is an open-chain compound, e.g. alkanes and acyclic aliphatic compounds * In mathematics: ** A graph without a cycle, especially *** A directed acyclic graph ** An acyclic complex Homological algebra is the branch of mathematics that studies homology in a general algebraic setting. It is a relatively young discipline, whose origins can be traced to investigations in combinatorial topology (a precursor to algebraic topology ... is a chain complex all of whose homology groups are zero * In economics, an economic indicator with little or no correlation to the business cycle {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Package Diagram
A package diagram in the Unified Modeling Language depicts the dependencies between the packages that make up a model. Overview In addition to the standard UML Dependency relationship, there are two special types of dependencies defined between packages: * package import * package merge A ''package import'' is "a relationship between an importing namespace and a package, indicating that the importing namespace adds the names of the members of the package to its own namespace." By default, an unlabeled dependency between two packages is interpreted as a package import relationship. In this relationship, elements within the target package will be imported into the source package. A ''package merge'' is "a directed relationship between two packages, that indicates that the contents of the two packages are to be combined. It is very similar to Generalisation in the sense that the source element conceptually adds the characteristics of the target element to its own characteristics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apache Maven
Maven is a build automation tool used primarily for Java projects. Maven can also be used to build and manage projects written in C#, Ruby, Scala, and other languages. The Maven project is hosted by the Apache Software Foundation, where it was formerly part of the Jakarta Project. Maven addresses two aspects of building software: how software is built and its dependencies. Unlike earlier tools like Apache Ant, it uses conventions for the build procedure. Only exceptions need to be specified. An XML file describes the software project being built, its dependencies on other external modules and components, the build order, directories, and required plug-ins. It comes with pre-defined targets for performing certain well-defined tasks such as compilation of code and its packaging. Maven dynamically downloads Java libraries and Maven plug-ins from one or more repositories such as the Maven 2 Central Repository, and stores them in a local cache. This local cache of downloaded arti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both. Communicating systems use well-defined formats for exchanging various messages. Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is typically independent of how it is to be implemented. Communication protocols have to be agreed upon by the parties involved. To reach an agreement, a protocol may be developed into a technical standard. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: ''protocols are to co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Bus
A software bus is a software architecture model where a shared communication channel facilitates connections and communication between software modules. This makes software buses conceptually similar to the bus term used in computer hardware for interconnecting pathways. In the early microcomputer era of the 1970s, Digital Research's operating system CP/M was often described as a ''software bus''. Lifeboat Associates, an early distributor of CP/M and later of MS-DOS software, had a whole product line named ''Software Bus''. D-Bus is used in many modern desktop environments to allow multiple processes to communicate with one another. Examples * Lifeboat Associates Software Bus-80 aka SB-80, a version of CP/M-80 for 8080/Z80 8-bit computers * Lifeboat Associates Software Bus-86 aka SB-86, a version of MS-DOS for x86 16-bit computers. * Component Object Model for in-process and interprocess communication. * D-Bus for interprocess communication. * Enterprise service bus for distri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dependency Inversion Principle
In object-oriented design, the dependency inversion principle is a specific methodology for loosely coupling 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: By dictating that high-level and low-level objects must depend on the same abstraction, this design principle the way some people may think about object-oriented programming. The idea behind points A and B of this principle is that when designing the interaction between a high-level module and a low-level one, the interaction should be thought of as an abstract interaction between them. This not only has implications on the design of the high-level module, but also on the low-level one: the low-level one should be designed with the interaction in mind and it may be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Package Principles
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 (package cohesion) and how these packages should relate with one another (package coupling). 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. See also * SOLID * Robert Cecil Martin Robert Cecil Martin (born 5 December 1952), colloquially called "Uncle Bob", is an American software engineer, instructor, and best-selling author. He is most recognized for developing many software design principles and for being a founder of t ... References * * * {{cite book , title=Agile Software Development, Principles, Patterns, and Practices , publisher=Prentice Hall , author=Martin, Robert C. , year=2002 , isbn=978-0135974445 , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circular Dependency
In software engineering, a circular dependency is a relation between two or more modules which either directly or indirectly depend on each other to function properly. Such modules are also known as mutually recursive. Overview Circular dependencies are natural in many domain models where certain objects of the same domain depend on each other. However, in software design, circular dependencies between larger software modules are considered an anti-pattern because of their negative effects. Despite this, such circular (or cyclic) dependencies have been found to be widespread among the source files of real-world software. Mutually recursive modules are, however, somewhat common in functional programming, where inductive and recursive definitions are often encouraged. Problems Circular dependencies can cause many unwanted effects in software programs. Most problematic from a software design point of view is the ''tight coupling'' of the mutually dependent modules which reduces or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
