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Entity–relationship Model
An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types). In software engineering, an ER model is commonly formed to represent things a business needs to remember in order to perform business processes. Consequently, the ER model becomes an abstract data model, that defines a data or information structure that can be implemented in a database, typically a relational database. Entity–relationship modeling was developed for database and design by Peter Chen and published in a 1976 paper, with variants of the idea existing previously. Today it is commonly used for teaching students the basics of database structure. Some ER models show super and subtype entities connected by generalization-specialization relationships, and an ER model can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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ER Diagram MMORPG
ER or Er may refer to: People * Er (biblical person), the eldest son of Judah in the biblical book of Genesis * Nie Er (1912–1935), Chinese composer * Elliot Rodger (July 24, 1991 – May 23, 2014), English-American incel mass shooter * A Royal cypher representing a monarch ** Elizabeth Regina (ER), the royal cypher of Elizabeth I ** Edward Rex (ER / EVIIR), the royal cypher of Edward VII ** Edward Rex (ER / EVIIIR), the royal cypher of Edward VIII ** Elizabeth II Regina (EIIR), the royal cypher of Elizabeth II Fictional characters * Er, a character in Plato's '' Myth of Er'' Arts, entertainment and media Music * ''Er'', an album by Nils Petter Molvær * "ER" (song), a 2012 single by Japanese boy band Kanjani Eight * "ER", a song by Royce da 5'9" featuring Kid Vishis from ''Success Is Certain'' Periodicals * '' Chico Enterprise-Record'', the daily newspaper of Chico, California Television * ''ER'' (TV series), a 1994–2009 American television medical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Database Table
In a database, a table is a collection of related data organized in table format; consisting of columns and rows. In relational databases, and flat file databases, a ''table'' is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows. Each row is identified by one or more values appearing in a particular column subset. A specific choice of columns which uniquely identify rows is called the primary key. "Table" is another term for "relation"; although there is the difference in that a table is usually a multiset (bag) of rows where a relation is a set and does not allow duplicates. Besides the actual data rows, tables generally have associated with them some metadata, such as constraints on the table or on the values within particular columns. The data in a table does not have to be physi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Relational Model
The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data are represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a relational database. The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries. Most relational databases use the SQL data definition and query language; these systems implement what can be regarded as an engineering approximation to the relational model. A '' table'' in a SQL database schema corresponds to a predicate variable; the contents of a tab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Logical Data Model
A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags. This is as opposed to a conceptual data model, which describes the semantics of an organization without reference to technology. Overview Logical data models represent the abstract structure of a domain of information. They are often diagrammatic in nature and are most typically used in business processes that seek to capture things of importance to an organization and how they relate to one another. Once validated and approved, the logical data model can become the basis of a physical data model and form the design of a database. Logical data models should be based on the structures identified in a preceding conceptual data model, since this describes the semantics of the informa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Conceptual Data Model
A conceptual schema or conceptual data model is a high-level description of informational needs underlying the design of a database. It typically includes only the core concepts and the main relationships among them. This is a high-level model with insufficient detail to build a complete, functional database. It describes the structure of the whole database for a group of users. The conceptual model is also known as the data model that can be used to describe the conceptual schema when a database system is implemented. It hides the internal details of physical storage and targets the description of entities, datatypes, relationships and constraints. Overview A conceptual schema is a map of concepts and their relationships used for databases. This describes the semantics of an organization and represents a series of assertions about its nature. Specifically, it describes the things of significance to an organization (''entity classes''), about which it is inclined to collec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Universe Of Discourse
In the formal sciences, the domain of discourse or universe of discourse (borrowing from the mathematical concept of ''universe'') is the set of entities over which certain variables of interest in some formal treatment may range. It is also defined as the collection of objects being discussed in a specific discourse. In model-theoretical semantics, a universe of discourse is the set of entities that a model is based on. The domain of discourse is usually identified in the preliminaries, so that there is no need in the further treatment to specify each time the range of the relevant variables. Many logicians distinguish, sometimes only tacitly, between the ''domain of a science'' and the ''universe of discourse of a formalization of the science''. Etymology The concept ''universe of discourse'' was used for the first time by George Boole (1854) on page 42 of his '' Laws of Thought'': The concept, probably discovered independently by Boole in 1847, played a crucial role i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Information
Information is an Abstraction, abstract concept that refers to something which has the power Communication, to inform. At the most fundamental level, it pertains to the Interpretation (philosophy), interpretation (perhaps Interpretation (logic), formally) of that which may be sensed, or their abstractions. Any natural process that is not completely random and any observable pattern in any Media (communication), medium can be said to convey some amount of information. Whereas digital signals and other data use discrete Sign (semiotics), signs to convey information, other phenomena and artifacts such as analog signals, analogue signals, poems, pictures, music or other sounds, and current (fluid), currents convey information in a more continuous form. Information is not knowledge itself, but the meaning (philosophy), meaning that may be derived from a representation (mathematics), representation through interpretation. The concept of ''information'' is relevant or connected t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Requirements Analysis
In systems engineering and software engineering, requirements analysis focuses on the tasks that determine the needs or conditions to meet the new or altered product or project, taking account of the possibly conflicting requirements of the various Stakeholder (corporate), stakeholders, ''analyzing'', ''documenting'', ''validating'', and ''managing'' software or system requirements. Requirements analysis is critical to the success or failure of systems or Software project management, software projects. The requirements should be documented, actionable, measurable, testable, traceable, related to identified business needs or opportunities, and defined to a level of detail sufficient for Systems design, system design. Overview Conceptually, requirements analysis includes three types of activities: *Requirements elicitation, Eliciting requirements: (e.g. the project charter or definition), business process documentation, and stakeholder interviews. This is sometimes also calle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Information System
An information system (IS) is a formal, sociotechnical, organizational system designed to collect, process, Information Processing and Management, store, and information distribution, distribute information. From a sociotechnical perspective, information systems comprise four components: task, people, structure (or roles), and technology. Information systems can be defined as an integration of components for collection, storage and data processing, processing of data, comprising digital products that process data to facilitate decision making and the data being used to provide information and contribute to knowledge. A computer information system is a system, which consists of people and computers that process or interpret information. The term is also sometimes used to simply refer to a computer system with software installed. "Information systems" is also an academic field of study about systems with a specific reference to information and the complementary networks of computer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |