Lattice-ordered abelian groups and perfect MV-algebras: a topos-theoretic perspective

We establish, generalizing Di Nola and Lettieri's categorical equivalence, a Morita-equivalence between the theory of lattice-ordered abelian groups and that of perfect MV-algebras. Further, after observing that the two theories are not bi-interpretable in the classical sense, we identify, by considering appropriate topos-theoretic invariants on their common classifying topos, three levels of bi-intepretability holding for particular classes of formulas: irreducible formulas, geometric sentences and imaginaries. Lastly, by investigating the classifying topos of the theory of perfect MV-algebras, we obtain various results on its syntax and semantics also in relation to the cartesian theory of the variety generated by Chang's MV-algebra, including a concrete representation for the finitely presentable models of the latter theory as finite products of finitely presentable perfect MV-algebras. Among the results established on the way, we mention a Morita-equivalence between the theory of lattice-ordered abelian groups and that of cancellative lattice-ordered abelian monoids with bottom element.Comment: 54 page

Error Analysis in the Teaching of English

The main purpose of this article is to discuss the importance of error analysis in the teaching of English as a foreign language. Although errors are bad things in learning English as a foreign language%2C error analysis is advantageous for both learners and teachers. For learners%2C error analysis is needed to show them in what aspect in grammar which is difficult for them%2C where as for teachers%2C it is required to evaluate themselves whether they are successful or not in teaching English.%0D%0AIn this article%2C the writer presented some English sentences containing grammatical errors. These grammatical errors were analyzed based on the theories presented by the linguists. This analysis aimed at showing the students the causes and kinds of the grammatical errors. By this way%2C the students are expected to increase their knowledge on the English grammar. Abstract in Bahasa Indonesia : errors%2C+mistake%2C+over+orrer%2C+covert+error%2C+interference%2C+overgeneralization%2C+grammar%2C+interlingual%2C+intralingual%2C+idiosyncrasies

Comparing the use of edited and unedited text in parser self-training

We compare the use of edited text in the form of newswire and unedited text in the form of discussion forum posts as sources for training material in a self-training experiment involving the Brown reranking parser and a test set of sentences from an online sports discussion forum. We find that grammars induced from the two automatically parsed corpora achieve similar Parseval f-scores, with the grammars induced from the discussion forum material being slightly superior. An error analysis reveals that the two types of grammars do behave differently