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Instance (database)
Instantiation or instance may refer to: Philosophy * A modern concept similar to ''participation'' in classical Platonism; see the Theory of Forms * The instantiation principle, the idea that in order for a property to exist, it must be had by some object or substance; the instance being a specific object rather than the idea of it * Universal instantiation * An instance (predicate logic), a statement produced by applying universal instantiation to a universal statement * Existential fallacy, also called existential instantiation * A substitution instance, a formula of mathematical logic that can be produced by substituting certain strings of symbols for others in formula, also can be used as the mathematical order to represent the data in an algorithm Computing * Instance (computer science), referring to any running process, or specifically to an object as an instance of a class * Table instance (or database instance), a concept in database design; see Row (database) * Creatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theory Of Forms
The theory of Forms or theory of Ideas is a philosophical theory, fuzzy concept, or world-view, attributed to Plato, that the physical world is not as real or true as timeless, absolute, unchangeable ideas. According to this theory, ideas in this sense, often capitalized and translated as "Ideas" or "Forms", are the non-physical essences of all things, of which objects and matter in the physical world are merely imitations. Plato speaks of these entities only through the characters (primarily Socrates) of his dialogues who sometimes suggests that these Forms are the only objects of study that can provide knowledge. The theory itself is contested from within Plato's dialogues, and it is a general point of controversy in philosophy. Nonetheless, the theory is considered to be a classical solution to the problem of universals. The early Greek concept of form precedes attested philosophical usage and is represented by a number of words mainly having to do with vision, sight, and ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instantiation Principle
The instantiation principle or principle of instantiation or principle of exemplification is the concept in metaphysics and logic (first put forward by David Malet Armstrong) that there can be no uninstantiated or unexemplified properties (or universals). In other words, it is impossible for a property to exist which is not had by some object. Consider a chair. Presumably chairs did not exist 150,000 years ago. Thus, according to the principle of instantiation, the property of being a chair did not exist 150,000 years ago either. Similarly, if all red objects were to suddenly go out of existence, then the property of being red would likewise go out of existence. To make the principle more plausible in the light of these examples, the existence of properties or universals is not tied to their actual existence now, but to their existence in space-time considered as a whole. Thus, any property which ''is'', ''has been'', or ''will be'' instantiated exists. The property of being red wou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universal Instantiation
In predicate logic, universal instantiation (UI; also called universal specification or universal elimination, and sometimes confused with '' dictum de omni'') is a valid rule of inference from a truth about each member of a class of individuals to the truth about a particular individual of that class. It is generally given as a quantification rule for the universal quantifier but it can also be encoded in an axiom schema. It is one of the basic principles used in quantification theory. Example: "All dogs are mammals. Fido is a dog. Therefore Fido is a mammal." Formally, the rule as an axiom schema is given as : \forall x \, A \Rightarrow A\, for every formula ''A'' and every term ''a'', where A\ is the result of substituting ''a'' for each ''free'' occurrence of ''x'' in ''A''. \, A\ is an instance of \forall x \, A. And as a rule of inference it is :from \vdash \forall x A infer \vdash A \ . Irving Copi noted that universal instantiation "... follows from variants of rule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instance (predicate Logic)
In predicate logic, universal instantiation (UI; also called universal specification or universal elimination, and sometimes confused with '' dictum de omni'') is a valid rule of inference from a truth about each member of a class of individuals to the truth about a particular individual of that class. It is generally given as a quantification rule for the universal quantifier but it can also be encoded in an axiom schema. It is one of the basic principles used in quantification theory. Example: "All dogs are mammals. Fido is a dog. Therefore Fido is a mammal." Formally, the rule as an axiom schema is given as : \forall x \, A \Rightarrow A\, for every formula ''A'' and every term ''a'', where A\ is the result of substituting ''a'' for each ''free'' occurrence of ''x'' in ''A''. \, A\ is an instance of \forall x \, A. And as a rule of inference it is :from \vdash \forall x A infer \vdash A \ . Irving Copi noted that universal instantiation "... follows from variants of rule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Existential Fallacy
The existential fallacy, or existential instantiation, is a formal fallacy. In the existential fallacy, one presupposes that a class has members when one is not supposed to do so; i.e., when one should not assume existential import. Not to be confused with the 'Affirming the consequent', which states "A causes B; B, therefore A". One example would be: "''Every unicorn has a horn on its forehead''". It does not imply that there are any unicorns at all in the world, and thus it cannot be assumed that, if the statement were true, somewhere there is a unicorn in the world (with a horn on its forehead). The statement, if assumed true, implies only that if there were any unicorns, each would definitely have a horn on its forehead. Overview An existential fallacy is committed in a medieval categorical syllogism because it has two universal premises and a particular conclusion with no assumption that at least one member of the class exists, an assumption which is not established by the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substitution Instance
Substitution is a fundamental concept in logic. A substitution is a syntactic transformation on formal expressions. To apply a substitution to an expression means to consistently replace its variable, or placeholder, symbols by other expressions. The resulting expression is called a substitution instance, or instance for short, of the original expression. Propositional logic Definition Where ''ψ'' and ''φ'' represent formulas of propositional logic, ''ψ'' is a substitution instance of ''φ'' if and only if ''ψ'' may be obtained from ''φ'' by substituting formulas for symbols in ''φ'', replacing each occurrence of the same symbol by an occurrence of the same formula. For example: ::(R → S) & (T → S) is a substitution instance of: ::P & Q and ::(A ↔ A) ↔ (A ↔ A) is a substitution instance of: ::(A ↔ A) In some deduction systems for propositional logic, a new expression (a proposition) may be entered on a line of a derivation if it is a substitution instanc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instance (computer Science)
In a computer system, any time a new context is created based on some model, it is said that the model has been instantiated. In practice, this instance usually has a data structure in common with other instances, but the values stored in the instances are separate. Changing the values in one instance will then not interfere with the values of some other instance. A compute instance can be software or hardware which can run code, for example a CPU, GPU or a virtual machine. Computer graphics In computer graphics, a polygonal model can be instantiated in order to be drawn several times in different locations in a scene. This is a technique that can be used to improve the performance of rendering, since the work needed to display each instance overlaps. Object-oriented programming In object-oriented programming (OOP), an instance is a concrete occurrence of any object, existing usually during the runtime of a computer program. Formally, "instance" is synonymous with "object" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Row (database)
In the context of a relational database, a row—also called a tuple—represents a single, implicitly structured data item in a table. In simple terms, a database table can be thought of as consisting of ''rows'' and columns. Cory Janssen, Techopedia, retrieved 27 June 2014 Each row in a table represents a set of related data, and every row in the table has the same structure. For example, in a table that represents companies, each row would represent a single company. Columns might represent things like company name, company street address, whether the company is publicly held, its VAT number, etc. In a table that represents ''the association'' of employees with depart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object (computer Science)
In computer science, an object can be a variable, a data structure, a function, or a method. As regions of memory, they contain value and are referenced by identifiers. In the object-oriented programming paradigm, ''object'' can be a combination of variables, functions, and data structures; in particular in class-based variations of the paradigm it refers to a particular instance of a class. In the relational model of database management, an object can be a table or column, or an association between data and a database entity (such as relating a person's age to a specific person). Object-based languages An important distinction in programming languages is the difference between an object-oriented language and an object-based language. A language is usually considered object-based if it includes the basic capabilities for an object: identity, properties, and attributes. A language is considered object-oriented if it is object-based and also has the capability of polymorphism, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Machine
In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination. Virtual machines differ and are organized by their function, shown here: * '' System virtual machines'' (also termed full virtualization VMs) provide a substitute for a real machine. They provide functionality needed to execute entire operating systems. A hypervisor uses native execution to share and manage hardware, allowing for multiple environments which are isolated from one another, yet exist on the same physical machine. Modern hypervisors use hardware-assisted virtualization, virtualization-specific hardware, primarily from the host CPUs. * Process virtual machines are designed to execute computer programs in a platform-independent environment. Some virtual machine emulators, such as QEMU and video ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instance Dungeon
In massively multiplayer online games, an instance is a special area, typically a dungeon, that generates a new copy of the location for each group, or for a certain number of players, that enters the area. Instancing, the general term for the use of this technique, addresses several problems encountered by players in the shared spaces of virtual worlds. It is not widely known when instances were first used in this genre. However, ''The Realm Online'' (1996) is sometimes credited as introducing the concept. Design considerations The problem can be stated as follows: every player wants to be "The Hero", slay "The Monster", rescue "The Princess", and obtain "The Magic Sword". When there are thousands of players all playing the same game, clearly not everyone can be the hero. The problem of everyone wanting to kill the same monster and gain the best treasure became obvious in the game ''EverQuest'', where several groups of players would compete and sometimes harass each other in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Body Of Knowledge
A body of knowledge (BOK or BoK) is the complete set of concepts, terms and activities that make up a professional domain, as defined by the relevant learned society or professional association.Oliver, G.R. (2012). ''Foundations of the Assumed Business Operations and Strategy Body of Knowledge (BOSBOK): An Outline of Shareable Knowledge'', p. 3. It is a type of knowledge representation by any knowledge organization. Several definitions of BOK have been developed, for example: * "Structured knowledge that is used by members of a discipline to guide their practice or work." "The prescribed aggregation of knowledge in a particular area an individual is expected to have mastered to be considered or certified as a practitioner." (BOK-def). Waite's pragmatic view is also worth noting (Ören 2005): "BOK is a stepping stone to unifying community" (Waite 2004). * The systematic collection of activities and outcomes in terms of their values, constructs, models, principles and instantiations, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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