Reinterpreting Compression in Infinitary Rewriting

Departing from a computational interpretation of compression in infinitary rewriting, we view compression as a degenerate case of standardisation. The change in perspective comes about via two observations: (a) no compression property can be recovered for non-left-linear systems and (b) some standardisation procedures, as a ‘side-effect’, yield compressed reductions

Notes on the Idea of a Species: A Look at Human/Neandertal Interbreeding

Unearthed within the limestone quarries that lie east of Dusseldorf in Germany, the first fossil to be recognized as an ancient hominin brought solid evidence to the table for starting to find answers to the question of where humans came from

Rewriting Mauritius: Ananda Devi's postcolonial self-translation

The Mauritian writer, Ananda Devi, once described the experience of translating her own French-language novel, Pagli, into English as ‘liberating, even exhilarating’, as compared with the more constrained, faithful practice of translating another writer’s work. Indeed, Devi goes so far as to assert that the English-language version of Pagli ‘is more of a rewriting than a translation’, so explicitly signalling the creative liberties that she takes with source text and culture. This article seeks to overcome the critical neglect of Devi’s fascinating self-translation, by exploring the many striking divergences—both stylistic excisions and narrative additions—between source and target texts, occasioned, at least in part, by the novel’s new, Anglophone Indian readership. It investigates, in particular, how Devi’s extensive additions of new material, particularly relating to questions of slavery and anti-black racism, seek to rewrite dominant national narratives which foreground Indo-Mauritians’ enduring diasporic links with India. Exploiting the creative freedom offered by self-translation, Devi’s English-language, Indian-published Pagli represents the author’s attempt to confront, and thereby begin to overcome, the deep and enduring divisions caused by Mauritius’s dual ‘crimes fondateurs’ of slavery and indenture. As our analysis of Ananda Devi’s rewriting of both her own text and, with it, of Mauritius’s past demonstrates, the author’s ‘liberating and exhilarating’ self-translation destabilises and refutes the traditional binary opposition between ‘original’ writing and derivative translation, revealing the many, creative and political ways in which meanings shift with language and audience

Exploring Conditional Rewriting Logic Computations

[EN] Trace exploration is concerned with techniques that allow computation traces to be dynamically searched for specific contents. Depending on whether the exploration is carried backward or forward, trace exploration techniques allow provenance tracking or impact tracking to be done. The aim of provenance tracking is to show how (parts of) a program output depends on (parts of) its input and to help estimate which input data need to be modified to accomplish a change in the outcome. The aim of impact tracking is to identify the scope and potential consequences of changing the program input. Rewriting Logic (RWL) is a logic of change that supplements (an extension of) the equational logic by adding rewrite rules that are used to describe (nondeterministic) transitions between states. In this paper, we present a rich and highly dynamic, parameterized technique for the forward inspection of RWL computations that allows the nondeterministic execution of a given conditional rewrite theory to be followed up in different ways. With this technique, an analyst can browse, slice, filter, or search the traces as they come to life during the program execution. The navigation of the trace is driven by a user-defined, inspection criterion that specifies the required exploration mode. By selecting different inspection criteria, one can automatically derive a family of practical algorithms such as program steppers and more sophisticatedThis work has been partially supported by the EU (FEDER) and the Spanish MEC project Ref. TIN2010-21062-C02-02, the Spanish MICINN complementary action Ref. TIN2009-07495-E, and by Generalitat Valenciana Ref. PROMETEO2011/052. This work was carried out during the tenure of D. Ballis' ERCIM "Alain Bensoussan" Postdoctoral Fellowship. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement N. 246016. F. Frechina was supported by FPU-ME grant AP2010-5681, and J. Sapina was supported by FPI-UPV grant SP2013-0083.Alpuente Frasnedo, M.; Ballis, D.; Frechina Navarro, F.; Sapiña Sanchis, J. (2015). Exploring Conditional Rewriting Logic Computations. Journal of Symbolic Computation. 69:3-39. https://doi.org/10.1016/j.jsc.2014.09.028S3396

Rewriting Transfinite Terms

We define rewriting over terms with positions of transfinite length

Simulating TRSs by minimal TRSs : a simple, efficient, and correct compilation technique

A simple, efficient, and correct compilation technique for left-linear Term Rewriting Systems (TRSs) is presented. TRSs are compiled into Minimal Term Rewriting Systems (MTRSs), a subclass of TRSs, presented in [KW95d]. In MTRSs, the rules have such a simple form that they can be seen as instructions for an easily implementable abstract machine, the Abstract Rewriting Machine (ARM). In the correctness proof, it is shown that the MTRS resulting from compilation of a TRS simulates neither too much (soundness) nor too little (completeness), nor does it introduce unwarranted infinite sequences (termination conservation). The compiler and its correctness proof are largely independent of the reduction strategy

Discriminating Lambda-Terms Using Clocked Boehm Trees

As observed by Intrigila, there are hardly techniques available in the lambda-calculus to prove that two lambda-terms are not beta-convertible. Techniques employing the usual Boehm Trees are inadequate when we deal with terms having the same Boehm Tree (BT). This is the case in particular for fixed point combinators, as they all have the same BT. Another interesting equation, whose consideration was suggested by Scott, is BY = BYS, an equation valid in the classical model P-omega of lambda-calculus, and hence valid with respect to BT-equality but nevertheless the terms are beta-inconvertible. To prove such beta-inconvertibilities, we employ `clocked' BT's, with annotations that convey information of the tempo in which the data in the BT are produced. Boehm Trees are thus enriched with an intrinsic clock behaviour, leading to a refined discrimination method for lambda-terms. The corresponding equality is strictly intermediate between beta-convertibility and Boehm Tree equality, the equality in the model P-omega. An analogous approach pertains to Levy-Longo and Berarducci Trees. Our refined Boehm Trees find in particular an application in beta-discriminating fixed point combinators (fpc's). It turns out that Scott's equation BY = BYS is the key to unlocking a plethora of fpc's, generated by a variety of production schemes of which the simplest was found by Boehm, stating that new fpc's are obtained by postfixing the term SI, also known as Smullyan's Owl. We prove that all these newly generated fpc's are indeed new, by considering their clocked BT's. Even so, not all pairs of new fpc's can be discriminated this way. For that purpose we increase the discrimination power by a precision of the clock notion that we call `atomic clock'.Comment: arXiv admin note: substantial text overlap with arXiv:1002.257