|
Federated Database
A federated database system (FDBS) is a type of meta-database management system (DBMS), which transparently maps multiple autonomous database systems into a single federated database. The constituent databases are interconnected via a computer network and may be geographically decentralized. Since the constituent database systems remain autonomous, a federated database system is a contrastable alternative to the (sometimes daunting) task of merging several disparate databases. A federated database, or virtual database, is a composite of all constituent databases in a federated database system. There is no actual data integration in the constituent disparate databases as a result of data federation. Through data abstraction, federated database systems can provide a uniform user interface, enabling users and clients to store and retrieve data from multiple noncontiguous databases with a single query—even if the constituent databases are heterogeneous. To this end, a federate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meta (prefix)
''Meta'' (from the , ''wikt:meta-, meta'', meaning 'after' or 'beyond') is an adjective meaning 'more comprehensive' or 'transcending'. In modern nomenclature, the prefix meta can also serve as a prefix meaning self-referential, as a field of study or endeavor (metatheory: theory about a theory; metamathematics: mathematical theories about mathematics; meta-axiomatics or meta-axiomaticity: axioms about axiomatic systems; metahumor: joking about the ways humor is expressed; etc.). Original Greek meaning In Ancient Greek, Greek, the prefix ''meta-'' is generally less esoteric than in English language, English; Greek ''meta-'' is equivalent to the Latin language, Latin words ''post-'' or ''ad-''. The use of the prefix in this sense occurs occasionally in English language, scientific English terms derived from Greek (language), Greek. For example, the term ''Metatheria'' (the name for the clade of marsupial mammals) uses the prefix ''meta-'' in the sense that the ''Metatheria'' occur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Area Network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of data and sharing network devices, such as printers. The LAN contrasts the wide area network (WAN), which not only covers a larger geographic distance, but also generally involves Leased line, leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business and personal computers. Ethernet and Wi-Fi are the two most common technologies used for local area networks; historical network technologies include ARCNET, Token Ring, and LocalTalk. Cabling Most wired network infrastructures utilize Category 5 cable, Category 5 or Category 6 cable, Category 6 twisted pair cabling with RJ45 (telecommunications), RJ45 compatible terminations. This medium provides physical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semantic Equivalence
{{about, semantic equivalence of metadata, the concept in mathematical logic, Logical equivalence, the concept in linguistic semantics, Semantic equivalence (linguistics) In computer metadata, semantic equivalence is a declaration that two data elements from different vocabularies contain data that has similar meaning. There are three types of semantic equivalence statements: * Class or concept equivalence. A statement that two high level concepts have similar or equivalent meaning. * Property or attribute equivalence. A statement that two properties, descriptors or attributes of classes have similar meaning. * Instance equivalence. A statement that two instances of data are the same or refer to the same instance. Example Assume that there are two organizations, each having a separate data dictionary. The first organization has a data element entry: PersonFamilyName The name of a person shared with other members of their family. and a second organization ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attribute (computing)
In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such. For clarity, attributes should more correctly be considered metadata. An attribute is frequently and generally a property of a property. However, in actual usage, the term attribute can and is often treated as equivalent to a property depending on the technology being discussed. An attribute of an object usually consists of a name and a value. For an element these can be a type and class name, while for a file these can be a name and an extension, respectively. Rules and typing * Rules: Each named attribute has an associated set of rules called operations: For example, one doesn't sum characters or manipulate and process an integer array the same way as an image object. Neither does one process text as if it was type of floating point ( decimal numbers). * Data types: It follows that an object d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data
Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted formally. A datum is an individual value in a collection of data. Data are usually organized into structures such as tables that provide additional context and meaning, and may themselves be used as data in larger structures. Data may be used as variables in a computational process. Data may represent abstract ideas or concrete measurements. Data are commonly used in scientific research, economics, and virtually every other form of human organizational activity. Examples of data sets include price indices (such as the consumer price index), unemployment rates, literacy rates, and census data. In this context, data represent the raw facts and figures from which useful information can be extracted. Data are collected using technique ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metadata
Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive information about a resource. It is used for discovery and identification. It includes elements such as title, abstract, author, and keywords. * Structural metadata – metadata about containers of data and indicates how compound objects are put together, for example, how pages are ordered to form chapters. It describes the types, versions, relationships, and other characteristics of digital materials. * Administrative metadata – the information to help manage a resource, like resource type, and permissions, and when and how it was created. * Reference metadata – the information about the contents and quality of Statistical data type, statistical data. * Statistical metadata – also called process data, may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cardinality
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb is ''pollex'' (compare ''hallux'' for big toe), and the corresponding adjective for thumb is ''pollical''. Definition Thumb and fingers The English word ''finger'' has two senses, even in the context of appendages of a single typical human hand: 1) Any of the five terminal members of the hand. 2) Any of the four terminal members of the hand, other than the thumb. Linguistically, it appears that the original sense was the first of these two: (also rendered as ) was, in the inferred Proto-Indo-European language, a suffixed form of (or ), which has given rise to many Indo-European-family words (tens of them defined in English dictionaries) that involve, or stem from, concepts of fiveness. The thumb shares the following with each of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CODASYL
CODASYL, the Conference/Committee on Data Systems Languages, was a consortium formed in 1959 to guide the development of a standard programming language that could be used on many computers. This effort led to the development of the programming language COBOL, the CODASYL Data Model, and other technical standards. CODASYL's members were individuals from industry and government involved in data processing activity. Its larger goal was to promote more effective data systems analysis, design, and implementation. The organization published specifications for various languages over the years, handing these over to official standards bodies (ISO, ANSI, or their predecessors) for formal standardization. History CODASYL is remembered almost entirely for two activities: its work on the development of the COBOL language and its activities in standardizing database interfaces. It also worked on a wide range of other topics, including end-user form interfaces and operating system co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Object-Oriented Modeling
Object-oriented modeling (OOM) is an approach to modeling an application that is used at the beginning of the software life cycle when using an object-oriented approach to software development. The software life cycle is typically divided up into stages going from abstract descriptions of the problem to designs then to code and testing and finally to deployment. Modeling is done at the beginning of the process. The reasons to model a system before writing the code are: *Communication. Users typically cannot understand programming language or code. Model diagrams can be more understandable and can allow users to give developers feedback on the appropriate structure of the system. A key goal of the Object-Oriented approach is to decrease the "semantic gap" between the system and the real world by using terminology that is the same as the functions that users perform. Modeling is an essential tool to facilitate achieving this goal . *Abstraction. A goal of most software methodologie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Model
A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to the properties of real-world entities. For instance, a data model may specify that the data element representing a car be composed of a number of other elements which, in turn, represent the color and size of the car and define its owner. The corresponding professional activity is called generally ''data modeling'' or, more specifically, '' database design''. Data models are typically specified by a data expert, data specialist, data scientist, data librarian, or a data scholar. A data modeling language and notation are often represented in graphical form as diagrams. Michael R. McCaleb (1999)"A Conceptual Data Model of Datum Systems". National Institute of Standards and Technology. August 1999. A data model can sometimes be referred to as a data structure, especially in the context of programming languages. Data models are often complemented by function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Schema
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term "wikt:schema, schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the database language. The states of a created conceptual schema are transformed into an explicit mapping, the database schema. This describes how real-world entities are Data modeling, modeled in the database. "A database schema specifies, based on the database administrator's knowledge of possible applications, the facts that can ent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
