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A BIDIRECTIONAL REFINEMENT ALGORITHM FOR THE CALCULUS OF (CO)INDUCTIVE CONSTRUCTIONS
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Formalizing Overlap Algebras in Matita
 UNDER CONSIDERATION FOR PUBLICATION IN MATH. STRUCT. IN COMP. SCIENCE
, 2010
"... We describe some formal topological results, formalized in Matita 1/2, presented in predicative intuitionistic logic and in terms of Overlap Algebras. Overlap Algebras are new algebraic structures designed to ease reasoning about subsets in an algebraic way within intuitionistic logic. We find that ..."
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We describe some formal topological results, formalized in Matita 1/2, presented in predicative intuitionistic logic and in terms of Overlap Algebras. Overlap Algebras are new algebraic structures designed to ease reasoning about subsets in an algebraic way within intuitionistic logic. We find that they also ease the formalization of formal topological results in an interactive theorem prover. Our main result is the existence of a functor between two categories of ‘generalized topological spaces’, one with points (Basic Pairs) and the other pointfree (Basic Topologies). The reported formalization is part as a wider scientific collaboration with the inventor of the theory, Giovanni Sambin. His goal is to verify in what sense, and with what difficulties, his theory is ‘implementable’. We check that all intermediate constructions respect the stringent size requirements imposed by predicative logic. The formalization is quite unusual, since it has to make explicit size information that is often hidden. We found that the version of Matita used for the formalization was largely inappropriate. The formalization drove several major improvements of Matita that will be integrated in the next major release (Matita 1.0). We show some motivating examples for these improvements, taken directly from the formalization. We also describe a possibly suboptimal solution in Matita 1/2, exploitable in other similar systems. We briefly discuss a better solution available in Matita 1.0.
Natural deduction environment for Matita
"... Abstract. Matita is a proof assistant characterised by a rich, user extensible, output facility based on a widget for the rendering of MathML Presentation, and by the automatic handling of overloading by means of a flexible disambiguation mechanism. We show how to use these features to obtain a simp ..."
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Abstract. Matita is a proof assistant characterised by a rich, user extensible, output facility based on a widget for the rendering of MathML Presentation, and by the automatic handling of overloading by means of a flexible disambiguation mechanism. We show how to use these features to obtain a simple learning environment for natural deduction, without modifying the source code or Matita. 1
Rating Disambiguation Errors ⋆
"... Abstract. Ambiguous notation is a powerful tool developed to deal with the complexity of mathematics without sacrificing clarity or conciseness. In the mechanized parsing of ambiguous terms, a disambiguation algorithm can be used to provide the system with the intelligence necessary to select valid ..."
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Abstract. Ambiguous notation is a powerful tool developed to deal with the complexity of mathematics without sacrificing clarity or conciseness. In the mechanized parsing of ambiguous terms, a disambiguation algorithm can be used to provide the system with the intelligence necessary to select valid interpretations for the overloaded symbols received in input. Disambiguation works by means of an incremental analysis of the input term, progressively discarding all invalid interpretations. As a result, if the input term cannot be disambiguated, many errors will be produced, only a handful of which are truly meaningful to the user. In this paper, we improve the existing technique to classify disambiguation errors by introducing a new heuristic to sort errors from the most meaningful to the least, showing that it can be implemented in a natural way in the existing disambiguation algorithm. We also describe a neat interface to present disambiguation errors to the user, suitable for the use in interactive theorem proving applications. 1
UITP 2010 Pollackinconsistency
"... For interactive theorem provers a very desirable property is consistency: it should not be possible to prove false theorems. However, this is not enough: it also should not be possible to think that a theorem that actually is false has been proved. More precisely: the user should be able to know wha ..."
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For interactive theorem provers a very desirable property is consistency: it should not be possible to prove false theorems. However, this is not enough: it also should not be possible to think that a theorem that actually is false has been proved. More precisely: the user should be able to know what it is that the interactive theorem prover is proving. To make these issues concrete we introduce the notion of Pollackconsistency. This property is related to a system being able to correctly parse formulas that it printed itself. In current systems it happens regularly that this fails. We argue that a good interactive theorem prover should be Pollackconsistent. We show with examples that many interactive theorem provers currently are not Pollackconsistent. Finally we describe a simple approach for making a system Pollackconsistent, which only consists of a small modification to the printing code of the system. The most intelligent creature in the universe is a rock. None would know it because they have lousy I/O. — quote from the Internet
A BIDIRECTIONAL REFINEMENT ALGORITHM FOR THE CALCULUS OF (CO)INDUCTIVE CONSTRUCTIONS
, 2011
"... Vol. 8 (1:18) 2012, pp. 1–49 ..."
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