This paper substantiates that experience by formalizing safety and liveness in a way that permits the relationship between safety and invariance and between liveness and wellfoundedness to be demonstrated for a large class of properties. In so doing, we give new characterizations of safety and liveness and prove that they satisfy the formal definitions in [Alpera & Schneider 85a]

Researchers in analog computation theory have shown that a recurrent neural network (RNN) can be built to simulate a Turing machine (Pollack, 1987b; Siegelmann & Sontag, 1995). Recently, we showed that it is possible to train RNNs which imple ment some aspects of analog computation theory-namely a network can develop trajectories that count symbols (Wiles & Elman, 1995). But what are the implications for psychological models of sequence processing based on RNNs? As a first step toward answering this question, we investigate an RNN in a psycholinguistically motivated task: predict the next letter in a simple Deterministic Context Free Language that has one level of center-embedding. We demonstrate how the network develops simple coordination between trajectories that enable it to perform limited counting, and in some cases generalize to longer strings. We geometrically identify and analyze several properties relevant for this task, including information loss that results from approaching attractors, divergence in phase space that is used to split states, and difficulty in learning temporal dependencies when the input-output probabilities overlap for different input symbols. 1.

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In this paper we present a specialised word generator, which has been aimed as an assistant tool for Basque troubadours. Such a tool allows verse-writers to generate all the words that match with a given word termination. We coped with some interesting aspects, i.e. the dimension of the generated list and the need of establishing an order of relevance among the listed items. This work can be seen as a way of reusing computational linguistic tools in the context of the Basque cultural means of expression. The technical foundations of this tool lie on a two-level morphological processor. The way in which words must be generated (starting from the end of the word) leads us to inverse the generation process. 3 `Bertsolaritza': What Is It? `Bertsolaritza' (Basque term for verse-making) is an oral or written literature form with old tradition and great popularity in the Basque Country. Similar forms are manifested in other countries like Cuba. While the written mode is similar to poetry...

We introduce a class of probability models for sequences of random variables with complex long-range dependency structure, called stochastic segment interaction models, motivated by problems arising in the analysis of biopolymer sequence data. We generalize and extend previous work in this area, and make explicit the relations to existing literature on hidden Markov models (HMMs) and “generalized ” HMMs. We show that this class of models allows for incorporation of non-local interaction information in biological sequence analysis. We demonstrate this approach by developing models for prediction of 3D contacts in protein sequences using models for amino acid dependencies in β-sheets. We provide algorithms for Bayesian inference on these models via dynamic programming and Markov chain Monte Carlo simulation. Results are presented from an application to protein structure prediction from sequence.

The main claim of this paper is that notions of implementation based on an isomorphic correspondence between physical and computational states are not tenable. Rather, "implementation" has to be based on the notion of "bisimulation" in order to be able to block unwanted implementation results and incorporate intuitions from computational practice. A formal definition of implementation is suggested, which satisfies theoretical and practical requirements and may also be used to make the functionalist notion of "physical realization" precise. The upshot of this new definition of implementation is that implementation cannot distinguish isomorphic bisimilar from non-isomporphic bisimilar systems anymore, thus driving a wedge between the notions of causal and computational complexity. While computationalism does not seem to be affected by this result, the consequences for functionalism are not clear and need further investigations. Keywords: computation, implementation, computational complexity, causal complexity, realization, functionalism, functional architecture, computationalism, cognitive science 1.

The purpose of this paper is to show how HPSG can be favourably simulated by a dependency grammar. We will be specially interested in the translation of the SLASH feature and we will see that, providing we accept to not put the constituency structure forward, linguistic phenomena using the SLASH feature can be interpreted in various ways, including a fondamental notion which will be named, following Tesniere, nucleus. 1 HEAD-MARKED PHRASE-STRUCTURE GRAMMARS AND DEPENDENCY GRAMMARS It is sometimes forgotten that a head marked phrase-structure tree can be canonically converted into a dependency tree. Much better, Gaifman 1965 proves that a (head marked) phrase-structure grammar which verifies a special condition of finiteness (which is verified by X-bar grammar and therefore by HPSG) can be converted into a dependency grammar. A dependency structure for a sentence is a one-to-one mapping between the nodes of a tree (the dependency tree) and the words of the sentence. In other words...

of Artificial Language Learning: a proposal for distinguishing the differences between human and nonhuman animal learners

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