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Command Query Responsibility Segregation
In information technology, Command Query Responsibility Segregation (CQRS) is a system architecture that extends the idea behind command–query separation Command-query separation (CQS) is a principle of imperative computer programming. It was devised by Bertrand Meyer as part of his pioneering work on the Eiffel programming language. It states that every method should either be a ''command'' tha ... to the level of services. Such a system will have separate interfaces to send queries and to send commands. As in CQS, fulfilling a query request will only retrieve data and will not modify the state of the system (with some exceptions like logging access), while fulfilling a command request will modify the state of the system. Many systems push the segregation to the data models used by the system. The models used to process queries are usually called ''read models'' and the models used to process commands ''write models''. References {{reflist External linksCQRS Journey by Mic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Information Technology
Information technology (IT) is the use of computers to create, process, store, retrieve, and exchange all kinds of data . and information. IT forms part of information and communications technology (ICT). An information technology system (IT system) is generally an information system, a communications system, or, more specifically speaking, a computer system — including all hardware, software, and peripheral equipment — operated by a limited group of IT users. Although humans have been storing, retrieving, manipulating, and communicating information since the earliest writing systems were developed, the term ''information technology'' in its modern sense first appeared in a 1958 article published in the ''Harvard Business Review''; authors Harold J. Leavitt and Thomas L. Whisler commented that "the new technology does not yet have a single established name. We shall call it information technology (IT)." Their definition consists of three categories: techniques for pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Systems Architecture
A system architecture is the conceptual model that defines the structure, behavior, and more views of a system. An architecture description is a formal description and representation of a system, organized in a way that supports reasoning about the structures and behaviors of the system. A system architecture can consist of system components and the sub-systems developed, that will work together to implement the overall system. There have been efforts to formalize languages to describe system architecture, collectively these are called architecture description languages (ADLs). Overview Various organizations can define systems architecture in different ways, including: * The fundamental organization of a system, embodied in its components, their relationships to each other and to the environment, and the principles governing its design and evolution. * A representation of a system, including a mapping of functionality onto hardware and software components, a mapping of the soft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command–query Separation
Command-query separation (CQS) is a principle of imperative computer programming. It was devised by Bertrand Meyer as part of his pioneering work on the Eiffel programming language. It states that every method should either be a ''command'' that performs an action, or a ''query'' that returns data to the caller, but not both. In other words, ''asking a question should not change the answer''. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Connection with design by contract Command-query separation is particularly well suited to a design by contract (DbC) methodology, in which the design of a program is expressed as assertions embedded in the source code, describing the state of the program at certain critical times. In DbC, assertions are considered design annotations—not program logic—and as such, their execution should not affect the program state. CQS is beneficial to DbC because any value-returni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
