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Belief Merging
Belief merging, also called belief fusion or propositional belief merging, is a process in which an individual agent aggregates possibly conflicting pieces of information, expressed in logical formulae, into a consistent knowledge-base. Applications include combining conflicting sensor information received by the same agent (see sensor fusion) and combining multiple databases to build an expert system. It also has applications in multi-agent systems. Approaches Combination In the combination approach, we take the union of the knowledge bases (a finite set of logical formulas). If the union is consistent, we are done. Otherwise, we select some maximal consistent subset of it. Baral, Kraus, Minker and Subrahmanian present algorithms for combining knowledge-bases consisting of first-order theories, and to resolve inconsistencies among them.Subrahamanian presents a uniform theoretical framework, based on ''annotated logics'', for combining multiple knowledge bases which may have in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logical Formula
In mathematical logic, propositional logic and predicate logic, a well-formed formula, abbreviated WFF or wff, often simply formula, is a finite sequence of symbols from a given alphabet that is part of a formal language. The abbreviation wff is pronounced "woof", or sometimes "wiff", "weff", or "whiff". A formal language can be identified with the set of formulas in the language. A formula is a syntactic object that can be given a semantic meaning by means of an interpretation. Two key uses of formulas are in propositional logic and predicate logic. Introduction A key use of formulas is in propositional logic and predicate logic such as first-order logic. In those contexts, a formula is a string of symbols φ for which it makes sense to ask "is φ true?", once any free variables in φ have been instantiated. In formal logic, proofs can be represented by sequences of formulas with certain properties, and the final formula in the sequence is what is proven. Although the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leximin Order
In mathematics, leximin order is a total preorder on finite-dimensional vectors. A more accurate but less common term is leximin preorder. The leximin order is particularly important in social choice theory and fair division. Definition A vector x = (''x''1, ..., ''x''''n'') is ''leximin-larger'' than a vector y = (''y''1, ..., ''y''''n'') if one of the following holds: * The smallest element of x is larger than the smallest element of y; * The smallest elements of both vectors are equal, and the second-smallest element of x is larger than the second-smallest element of y; * ... * The ''k'' smallest elements of both vectors are equal, and the (''k''+1)-smallest element of x is larger than the (''k''+1)-smallest element of y. Examples The vector (3,5,3) is leximin-larger than (4,2,4), since the smallest element in the former is 3 and in the latter is 2. The vector (4,2,4) is leximin-larger than (5,3,2), since the smallest elements in both are 2, but the second-smallest elem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belief Aggregation
Belief aggregation, also called risk aggregation, opinion aggregation or probabilistic opinion pooling, is a process in which different probability distributions, produced by different experts, are combined to yield a single probability distribution. Background Expert opinions are often uncertain. Rather than saying e.g. "it will rain tomorrow", a weather expert may say "it will rain with probability 70% and be sunny with probability 30%". Such a statement is called a belief. Different experts may have different beliefs; for example, a different weather expert may say "it will rain with probability 60% and be sunny with probability 40%". In other words, each expert has a subjeciive probability distribution over a given set of outcomes. A belief aggregation rule is a function that takes as input two or more probability distributions over the same set of outcomes, and returns a single probability distribution over the same space. Applications Documented applications of belief agg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belief Revision
Belief revision (also called belief change) is the process of changing beliefs to take into account a new piece of information. The formal logic, logical formalization of belief revision is researched in philosophy, in databases, and in artificial intelligence for the design of intelligent agent, rational agents. What makes belief revision non-trivial is that several different ways for performing this operation may be possible. For example, if the current knowledge includes the three facts "A is true", "B is true" and "if A and B are true then C is true", the introduction of the new information "C is false" can be done preserving consistency only by removing at least one of the three facts. In this case, there are at least three different ways for performing revision. In general, there may be several different ways for changing knowledge. Revision and update Two kinds of changes are usually distinguished: ; update : the new information is about the situation at present, while t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Judgement Aggregation
Belief aggregation, also called risk aggregation, opinion aggregation or probabilistic opinion pooling, is a process in which different probability distributions, produced by different experts, are combined to yield a single probability distribution. Background Expert opinions are often uncertain. Rather than saying e.g. "it will rain tomorrow", a weather expert may say "it will rain with probability 70% and be sunny with probability 30%". Such a statement is called a belief. Different experts may have different beliefs; for example, a different weather expert may say "it will rain with probability 60% and be sunny with probability 40%". In other words, each expert has a subjeciive probability distribution over a given set of outcomes. A belief aggregation rule is a function that takes as input two or more probability distributions over the same set of outcomes, and returns a single probability distribution over the same space. Applications Documented applications of belief agg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Social Epistemology
Social epistemology refers to a broad set of approaches that can be taken in epistemology (the study of knowledge) that construes human knowledge as a collective achievement. Another way of characterizing social epistemology is as the evaluation of the social dimensions of knowledge or information. As a field of inquiry in analytic philosophy, social epistemology deals with questions about knowledge in social contexts, meaning those in which knowledge attributions cannot be explained by examining individuals in isolation from one another. The most common topics discussed in contemporary social epistemology are testimony (e.g. "When does a belief that x is true which resulted from being told 'x is true' constitute knowledge?"), peer disagreement (e.g. "When and how should I revise my beliefs in light of other people holding beliefs that contradict mine?"), and group epistemology (e.g. "What does it mean to attribute knowledge to groups rather than individuals, and when are such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiwinner Voting
Multiwinner or committee voting refers to electoral systems that elect several candidates at once. Such methods can be used to elect parliaments or committees. Goals There are many scenarios in which multiwinner voting is useful. They can be broadly classified into three classes, based on the main objective in electing the committee: # Excellence. Here, voters judge the quality of each candidate individually. The goal is to find the "objectively" best candidates. An example application is shortlisting: selecting, from a list of candidate employees, a small set of finalists, who will proceed to the final stage of evaluation (e.g. using an interview). Here, each candidate is evaluated independently of the others. If two candidates are similar, then probably both will be elected or both will be rejected. # Diversity. Here, the elected candidates should be as ''different'' as possible. For example, suppose the contest is about choosing locations for two fire stations or other fac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proportional Approval Voting
Proportional approval voting (PAV) is a proportional electoral system for multiwinner elections. It is a multiwinner approval method that extends the D'Hondt method of apportionment commonly used to calculate apportionments for party-list proportional representation. However, PAV allows voters to support only the candidates they approve of, rather than being forced to approve or reject all candidates on a given party list. In PAV, voters cast approval ballots marking all candidates they approve of; each voter's ballot is then treated as if all candidates on the ballot were on their own "party list." Seats are then apportioned between candidates in a way that ensures all coalitions are represented proportionally. History PAV is a special case of Thiele's voting rule, proposed by Thorvald N. Thiele. It was used in combination with ranked voting in the Swedish elections from 1909 to 1921 for distributing seats within parties and in local elections. PAV was rediscovered by For ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Justified Representation
Justified representation (JR) is a criterion of fairness in multiwinner approval voting. It can be seen as an adaptation of the proportional representation criterion to approval voting. Background Proportional representation (PR) is an important consideration in designing electoral systems. It means that the various groups and sectors in the population should be represented in the parliament in proportion to their size. The most common system for ensuring proportional representation is the party-list system. In this system, the candidates are partitioned into parties, and each citizen votes for a single party. Each party receives a number of seats proportional to the number of citizens who voted for it. For example, for a parliament with 10 seats, if exactly 50% of the citizens vote for party A, exactly 30% vote for party B, and exactly 20% vote for party C, then proportional representation requires that the parliament contains exactly 5 candidates from party A, exactly 3 can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gibbard–Satterthwaite Theorem
The Gibbard–Satterthwaite theorem is a theorem in social choice theory. It was first conjectured by the philosopher Michael Dummett and the mathematician Robin Farquharson in 1961 and then proved independently by the philosopher Allan Gibbard in 1973 and economist Mark Satterthwaite in 1975. It deals with deterministic ordinal electoral systems that choose a single winner, and shows that for every voting rule of this form, at least one of the following three things must hold: # The rule is dictatorial, i.e. there exists a distinguished voter who can choose the winner; or # The rule limits the possible outcomes to two alternatives only; or # The rule is not straightforward, i.e. there is no single always-best strategy (one that does not depend on other voters' preferences or behavior). Gibbard's proof of the theorem is more general and covers processes of collective decision that may not be ordinal, such as cardinal voting. Gibbard's 1978 theorem and Hylland's theorem are e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arrow's Impossibility Theorem
Arrow's impossibility theorem is a key result in social choice theory showing that no ranked-choice procedure for group decision-making can satisfy the requirements of rational choice. Specifically, Arrow showed no such rule can satisfy the independence of irrelevant alternatives axiom. This is the principle that a choice between two alternatives and should not depend on the quality of some third, unrelated option, . The result is often cited in discussions of voting rules, where it shows no ranked voting rule to eliminate the spoiler effect. This result was first shown by the Marquis de Condorcet, whose voting paradox showed the impossibility of logically-consistent majority rule; Arrow's theorem generalizes Condorcet's findings to include non-majoritarian rules like collective leadership or consensus decision-making. While the impossibility theorem shows all ranked voting rules must have spoilers, the frequency of spoilers differs dramatically by rule. Plurality-rule me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strategyproofness
In mechanism design, a strategyproof (SP) mechanism is a game form in which each player has a weakly- dominant strategy, so that no player can gain by "spying" over the other players to know what they are going to play. When the players have private information (e.g. their type or their value to some item), and the strategy space of each player consists of the possible information values (e.g. possible types or values), a truthful mechanism is a game in which revealing the true information is a weakly-dominant strategy for each player. An SP mechanism is also called dominant-strategy-incentive-compatible (DSIC), to distinguish it from other kinds of incentive compatibility. A SP mechanism is immune to manipulations by individual players (but not by coalitions). In contrast, in a group strategyproof mechanism, no group of people can collude to misreport their preferences in a way that makes every member better off. In a strong group strategyproof mechanism, no group of people can c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
