in Intellectual Property Rights in a Networked World, eds. H. Tavani and R. Spinello, 2004.

Many of the contemporary disagreements regarding privacy are conceptual in nature. They concern the meaning or definition of privacy and the analytic basis of distinguishing privacy rights from other kinds of rights recognized within moral, political, or legal theories. The two main alternatives within this debate include reductionist views, which seek a narrow account of the kinds of invasions or intrusions distinctly involving privacy losses, and anti-reductionist theories, which treat a much broader array of interferences with a person as separate (...) and irreducible kinds of privacy invasions. Other theorists have expressed doubts about the prospects for achieving greater analytical precision even within a fairly expansive anti-reductionist approach. However, a reductionist privacy definition is defended in this article, and its primary theoretical virtues are its ability to unify and explain the insights of several competing definitions and its role in developing an account of privacy rights that is both internally coherent and consistent with a plausible understanding of the theoretical basis for a number of related rights. (shrink)

This research is conducted by the Intellectual Property and Policy Research Group at the W. Maurice Young Centre for Applied Ethics at the University of British Columbia. It is part of the GE3LS component of the Genome Canada Project "Dissecting Gene Expression Networks in Mammalian Organogenesis," MORGEN, which is located principally at the British Columbia Cancer Agency, Vancouver, British Columbia, Canada. The project is involved in upstream, basic genomic research. Part of this work includes the characterization of gene regulatory mechanisms (...) governing organogenesis with a special focus on the heart, liver and pancreas. This paper serves as an introduction to both the MORGEN case study and the role of alternative mechanisms, such as open source. We discuss interim research results as they relate to our broader study of the relationship between open science, commercialization and technology transfer offices. The role of technology transfer offices is central to our analysis and is viewed as a key factor in implementing Genome Canada policies and principles associated with IP and commercialization. (shrink)

Although numerical systems have been regarded as static models of a symbolic system and treated as mythological behavior, it is postulated that these systems are more profitably analyzed as dynamic models, better understood as ritual behavior. As ritual, numerical systems, limited in number and expressive of rhythmicity, contribute to the biogenetic structuralist's notion of “equilibration” between the central nervous system and the environment.The relationship between concrete and abstract numeration is also examined, showing that counting behavior, requiring asymmetrical use of (...) the hands, may contribute to understanding the relationships between handedness and brain hemisphericity, as well as enumeration and memorization. (shrink)

Evil remains a primary source of inquiry in contemporary literature of French expression, even among its most secular writers. In considering French-speaking authors from France, Belgium, the United States, the Maghreb, and Sub-Saharan Africa, this collection delineates a rich international perspective on some of the most disturbing events of our time. Each essay testifies to the urgency expressed in works of fiction to give an account of human catastrophes, from the Shoah and the Rwandan genocide to the terrorist attacks of (...) September 11, and the ongoing oppression of women in Islamic nations. Themes underlying this volume include an investigation into the origins of evil, its representations in writing, and the ethical responsibilities of authors who write on human suffering. Contemporary fiction on evil confronts us with fundamental questions: Can evil be attributed to intentionality, is evil "subconscious," or is it the result of impersonal forces? Which styles of writing are ethically appropriate or effective for depicting evil? Can we speak of a veritable "poetics of evil" shared by contemporary authors? When does a literary text on evil become "evil"? In providing informed and nuanced answers to these important questions, the scholars engage in crucial theories of psychoanalysis, post-structuralism, and post-modernism, address a number of issues raised by trauma and genocide studies, and draw from critical frameworks in literary theory on testimony, the limits of representing the extreme, and "transgressive" writing. (shrink)

Previous accounts of hedges assume that they cause language to become vague or fuzzy (Lakoff 1973); however, hedges can actually sharpen numerical concepts by giving explicit information about approximation, especially where bare numbers appear misleadingly round or precise. They can also tell hearers about the direction of approximation (greater or less than). This article provides a first empirical account of interactions between hedging and rounding in numerical expressions. We demonstrate that hedges occur more commonly with round numbers than with non-round (...) ones. However, we also provide evidence from user studies that in the absence of hedges, readers interpret round numbers as approximations and non-round ones as precise; and that placing a hedge before a round number has no effect on its interpretation, whereas placing it before a non-round number shifts people’s interpretations from precise towards approximate. We attempt to explain this conundrum. (shrink)

Previous accounts of hedges assume that they cause language to become vague or fuzzy ; however, hedges can actually sharpen numerical concepts by giving explicit information about approximation, especially where bare numbers appear misleadingly round or precise. They can also tell hearers about the direction of approximation. This article provides a first empirical account of interactions between hedging and rounding in numerical expressions. We demonstrate that hedges occur more commonly with round numbers than with non-round ones. However, we also provide (...) evidence from user studies that in the absence of hedges, readers interpret round numbers as approximations and non-round ones as precise; and that placing a hedge before a round number has no effect on its interpretation, whereas placing it before a non-round number shifts people’s interpretations from precise towards approximate. We attempt to explain this conundrum. (shrink)

This paper reports research on the influence of corporate and individual characteristics on managers'' social orientation in Germany. The results indicate that mid-level managers expressed a significantly lower social orientation than low-level managers, and that job activity did not impact social orientation. Female respondents expressed a higher social orientation than male respondents. No impact of the political system origin (former East Germany versus former West Germany) on social orientation was shown. Overall, corporate position had a significantly higher impact on social (...) orientation than did the characteristics of the individuals surveyed. (shrink)

A substantial amount of recent work in natural language generation has focused on the generation of ‘‘one‐shot’’ referring expressions whose only aim is to identify a target referent. Dale and Reiter's Incremental Algorithm (IA) is often thought to be the best algorithm for maximizing the similarity to referring expressions produced by people. We test this hypothesis by eliciting referring expressions from human subjects and computing the similarity between the expressions elicited and the ones generated by algorithms. It turns out that (...) the success of the IA depends substantially on the ‘‘preference order’’ (PO) employed by the IA, particularly in complex domains. While some POs cause the IA to produce referring expressions that are very similar to expressions produced by human subjects, others cause the IA to perform worse than its main competitors; moreover, it turns out to be difficult to predict the success of a PO on the basis of existing psycholinguistic findings or frequencies in corpora. We also examine the computational complexity of the algorithms in question and argue that there are no compelling reasons for preferring the IA over some of its main competitors on these grounds. We conclude that future research on the generation of referring expressions should explore alternatives to the IA, focusing on algorithms, inspired by the Greedy Algorithm, which do not work with a fixed PO. (shrink)

A substantial amount of recent work in natural language generation has focused on the generation of ‘‘one-shot’’ referring expressions whose only aim is to identify a target referent. Dale and Reiter's Incremental Algorithm (IA) is often thought to be the best algorithm for maximizing the similarity to referring expressions produced by people. We test this hypothesis by eliciting referring expressions from human subjects and computing the similarity between the expressions elicited and the ones generated by algorithms. It turns out that (...) the success of the IA depends substantially on the ‘‘preference order’’ (PO) employed by the IA, particularly in complex domains. While some POs cause the IA to produce referring expressions that are very similar to expressions produced by human subjects, others cause the IA to perform worse than its main competitors; moreover, it turns out to be difficult to predict the success of a PO on the basis of existing psycholinguistic findings or frequencies in corpora. We also examine the computational complexity of the algorithms in question and argue that there are no compelling reasons for preferring the IA over some of its main competitors on these grounds. We conclude that future research on the generation of referring expressions should explore alternatives to the IA, focusing on algorithms, inspired by the Greedy Algorithm, which do not work with a fixed PO. (shrink)

In Entities and Indices, M. J. Cresswell argued that a first-order modal language can reach the expressive power of natural-language modal discourse only if we give to the formal language a semantics with indices containing infinite possible worlds and we add to it an infinite collection of operators $${{\varvec{actually}}}_n$$ actually n and $$ Ref _n$$ R e f n which store and retrieve worlds. In the fourth chapter of the book, Cresswell gave a proof that the resulting intensional (...) language, which he called $${\mathscr {L}}^*$$ L ∗, is as expressive as an extensional variant of it, called $${\mathscr {L}}$$ L, which has full quantification over worlds. In both linguistics and philosophy, Cresswell’s book has been viewed as offering a compelling argument for preferring extensional systems in the study of natural language. In this paper, after providing a model-theoretic definition of the relation being as expressive as that can be applied to Cresswell’s languages $${\mathscr {L}}$$ L and $${\mathscr {L}}^*$$ L ∗, we show that the intensional language $${\mathscr {L}}^*$$ L ∗ is not as expressive as the extensional language $${\mathscr {L}}$$ L. This result, we claim, undermines Cresswell’s argument to the effect that English modal discourse has the power of explicit quantification over worlds. Additionally, we show that $${\mathscr {L}}^*$$ L ∗ does become as expressive as $${\mathscr {L}}$$ L when we add Cresswell’s operator of universal modality $$\square $$ □ to $${\mathscr {L}}^*$$ L ∗, which provides an extra amount of expressive power. Recently, I. Yanovich has advocated a view that is similar to ours in important respects. At the end of the paper we offer a short discussion of his formalism. (shrink)

We investigate the expressive power of memory logics. These are modal logics extended with the possibility to store (or remove) the current node of evaluation in (or from) a memory, and to perform membership tests on the current memory. From this perspective, the hybrid logic (↓), for example, can be thought of as a particular case of a memory logic where the memory is an indexed list of elements of the domain.

Natural language provides motivation for studying modal backwards-looking operators such as “now”, “then” and “actually” that evaluate their argument formula at some previously considered point instead of the current one. This paper investigates the expressive power over models of both propositional and first-order basic modal language enriched with such operators. Having defined an appropriate notion of bisimulation for first-order modal logic, I show that backwards-looking operators increase its expressive power quite mildly, contrary to beliefs widespread among (...) philosophers of language and formal semanticists. That in turn presents a strong argument for the use of operator-based systems in the semantics of natural language, instead of systems with explicit quantification over worlds and times that have become a de-facto standard for such applications. The popularity of such explicit-quantification systems is shown to be based on the misinterpretation of a claim by Cresswell, which led many philosophers and linguists to assume that introducing “now” and “then” is expressively equivalent to explicitly quantifying over worlds and times. (shrink)

It is shown that the expressive power of second-order propositional modal logic whose modalities are S4.2 or weaker is the same as that of second-order predicate logic.

In Wehmeier (J Philos Log 33:607–630, 2004) we are presented with the subjunctive modal language, a way of dealing with the expressive inadequacy of modal logic by marking atomic predicates as being either in the subjunctive or indicative mood. Wehmeier claims that this language is expressively equivalent to the standard actuality language, and that despite this the marked-unmarked dichotomies are not the same in the two languages. In this paper we will attend to Wehmeier’s argument that this is the (...) case, and show that this conclusion rests on what might be considered an uncharitable stipulation concerning what it is for a formula in the actuality language to be true in a model. (shrink)

There are two perspectives from which formal theories can be viewed. On the one hand, one can take a theory to be about some privileged models. On the other hand, one can take all models of a theory to be on a par. In contrast with what is usually done in philosophical debates, we adopt the latter viewpoint. Suppose that from this perspective we want to add an adequate truth predicate to a background theory. Then on the one hand the (...) truth theory ought to be semantically conservative over the background theory. At the same time, it is generally recognised that the central function of a truth predicate is an expressive one. A truth predicate ought to allow us to express propositions that we could not express before. In this article we argue that there are indeed natural truth theories which satisfy both the demand of semantical conservativeness and the demand of adequately extending the expressive power of our language. (shrink)

Natural deduction systems were motivated by the desire to define the meaning of each connective by specifying how it is introduced and eliminated from inference. In one sense, this attempt fails, for it is well known that propositional logic rules underdetermine the classical truth tables. Natural deduction rules are too weak to enforce the intended readings of the connectives; they allow non-standard models. Two reactions to this phenomenon appear in the literature. One is to try to restore the standard readings, (...) for example by adopting sequent rules with multiple conclusions. Another is to explore what readings the natural deduction rules do enforce. When the notion of a model of a rule is generalized, it is found that natural deduction rules express “intuitionistic” readings of their connectives. A third approach is presented here. The intuitionistic readings emerge when models of rules are defined globally, but the notion of a local model of a rule is also natural. Using this benchmark, natural deduction rules enforce exactly the classical readings of the connectives, while this is not true of axiomatic systems. This vindicates the historical motivation for natural deduction rules. One odd consequence of using the local model benchmark is that some systems of propositional logic are not complete for the semantics that their rules express. Parallels are drawn with incompleteness results in modal logic to help make sense of this. (shrink)

We study the expressive power in the finite of the logic Fixed-Point+Counting, the extension of first-order logic which is obtained through adding both the fixed-point constructor and the ability to count. To this end an isomorphism preserving (`generic') model of computation is introduced whose PTime restriction exactly corresponds to this level of expressive power, while its PSpace restriction corresponds to While+Counting. From this model we obtain a normal form which shows a rather clear separation of the (...) relational vs. the arithmetical side of the algorithms involved. In parallel, we study the relations of Fixed-Point+Counting with the infinitary logics L r ∞ω (∃ ≥ m ) m∈ω and the corresponding pebble games. The main result, however, involves the concept of an arithmetical invariant. By this we mean a functor taking every finite relational structure to an expansion of (an initial segment of) the standard arithmetical structure. In particular its values are linearly ordered structures. We establish the existence of a family of arithmetical invariants (J r ) r≥ 1 with the following properties: $\bullet$ The invariants themselves can be evaluated in polynomial time. $\bullet$ A class of finite relational structures is definable in Fixed-Point+Counting if and only if membership can be decided in polynomial time on the basis of the values of one of the invariants. $\bullet$ The invariant J r classifies all finite relational structures exactly up to equivalence with respect to the logic L r ∞ω (∃ ≥ m ) m∈ω . We also give a characterization of Fixed-Point+Counting in terms of sequences of formulae in the L r ωω (∃ ≥ m ) m∈ω : It corresponds exactly to the polynomial time computable families (φ n ) n∈ω in these logics. Towards a positive assessment of the expressive power of Fixed-Point+Counting, it is shown that the natural extension of fixed-point logic by Lindström quantifiers, which capture all the PTime computable properties of cardinalities of definable predicates, is strictly weaker than what we get here. This implies in particular that every extension of fixed-point logic by means of monadic Lindstrom quantifiers, which stays within PTime, must be strictly contained in Fixed-Point+Counting. (shrink)

The aim of the paper is to analyze the expressive power of the square operator of Łukasiewicz logic: ∗x=x⊙x⁠, where ⊙ is the strong Łukasiewicz conjunction. In particular, we aim at understanding and characterizing those cases in which the square operator is enough to construct a finite MV-chain from a finite totally ordered set endowed with an involutive negation. The first of our main results shows that, indeed, the whole structure of MV-chain can be reconstructed from the involution (...) and the Łukasiewicz square operator if and only if the obtained structure has only trivial subalgebras and, equivalently, if and only if the cardinality of the starting chain is of the form n+1 where n belongs to a class of prime numbers that we fully characterize. Secondly, we axiomatize the algebraizable matrix logic whose semantics is given by the variety generated by a finite totally ordered set endowed with an involutive negation and Łukasiewicz square operator. Finally, we propose an alternative way to account for Łukasiewicz square operator on involutive Gödel chains. In this setting, we show that such an operator can be captured by a rather intuitive set of equations. (shrink)

A first order representation (f.o.r.) in topology is an assignment of finitary relational structures of the same type to topological spaces in such a way that homeomorphic spaces get sent to isomorphic structures. We first define the notions "one f.o.r. is at least as expressive as another relative to a class of spaces" and "one class of spaces is definable in another relative to an f.o.r.", and prove some general statements. Following this we compare some well-known classes of spaces (...) and first order representations. A principal result is that if X and Y are two Tichonov spaces whose posets of zero-sets are elementarily equivalent then their respective rings of bounded continuous real-valued functions satisfy the same positive-universal sentences. The proof of this uses the technique of constructing ultraproducts as direct limits of products in a category theoretic setting. (shrink)

This paper is about the development of logic in the Aristotelian tradition, from Aristotle to the mid-fourteenth century. I will compare four systems of logic with regard to their expressive power. 1. Aristotle’s own logic, based mostly on chapters 1-2 and 4-7 of his Prior Analytics 2. An expanded version of Aristotle’s logic that one finds, e.g., in Sherwood’s Introduction to Logic and Peter of Spain’s Tractatus 3-5. Versions of the logic of later supposition theorists such as William (...) Ockham, John Buridan, and Paul of Venice. Version 4 is the logic without relatives ; version 5 adds relatives. I am ignoring modals, conditionals that are not ut nunc, infinitizing negation, exclusives and exceptives, all exponibles, all insolubles, and terms with simple or material supposition, ampliation and restriction, and many other things. (shrink)

Many authors have noted that there are types of English modal sentences cannot be formalized in the language of basic first-order modal logic. Some widely discussed examples include “There could have been things other than there actually are” and “Everyone who is actually rich could have been poor.” In response to this lack of expressive power, many authors have discussed extensions of first-order modal logic with two-dimensional operators. But claims about the relative expressive power of these (...) extensions are often justified only by example rather than by rigorous proof. In this paper, we provide proofs of many of these claims and present a more complete picture of the expressive landscape for such languages. (shrink)

According to the influential “expressive” argument for hate speech laws, legal restrictions on hate speech are justified, in significant part, because they powerfully express opposition to hate speech. Yet the expressive argument faces a challenge: why couldn't we communicate opposition to hate speech via counterspeech, rather than bans? I argue that the expressive argument cannot address this challenge satisfactorily. Specifically, I examine three considerations that purport to explain bans’ expressive distinctiveness: considerations of strength; considerations of directness; (...) and considerations of complicity. These considerations either fail to establish that bans are expressively superior to counterspeech, or presuppose that bans successfully deter hate speech. This result severely undercuts the expressive argument's appeal. First, contrary to what its proponents suggest, this argument fails to circumvent the protracted empirical controversies surrounding bans’ effectiveness as deterrents. Second, the expressive argument appears redundant, because bans are expressively distinctive only insofar as hate speech is already suppressed. (shrink)

The present text discusses whether there is a tension between aphorisms 6.1-6.13 of the Tractatus and the Church-Turing theorem about the decidability of predicate logic. We attempt to establish the following points: (i) Aphorisms 6.1-6.13 are not consistent with the Church-Turing theorem. (ii) The logical symbolism of the Tractatus, built from the N-operator, can (and should) be interpreted as expressively complete with respect to first-order formulas. (iii) Wittgenstein’s reasons for believing that Logic is decidable were purely philosophical and the undecidability (...) result shows that there are aspects of his criticisms of Frege and Russell that become unjustified in light of these results. (shrink)

We illustrate, with three examples, the interaction between boolean and modal connectives by looking at the role of truth-functional reasoning in the provision of completeness proofs for normal modal logics. The first example (§ 1) is of a logic (more accurately: range of logics) which is incomplete in the sense of being determined by no class of Kripke frames, where the incompleteness is entirely due to the lack of boolean negation amongst the underlying non-modal connectives. The second example (§ 2) (...) focusses on the breakdown, in the absence of boolean disjunction, of the usual canonical model argument for the logic of dense Kripke frames, though a proof of incompleteness with respect to the Kripke semantics is not offered. An alternative semantic account is developed, in terms of which a completeness proof can be given, and this is used (§ 3) in the discussion of the third example, a bimodal logic which is, as with the first example, provably incomplete in terms of the Kripke semantics, the incompleteness being due to the lack of disjunction (as a primitive or defined boolean connective). (shrink)

In her later writings Jean Hampton develops an expressive theory of punishment she takes to be retributivist. Unlike Feinberg, Hampton claims wrongdoings as well as punishments are expressive. Wrongdoings assert that the victim is less valuable than victimizer. On her view we are obligated to punish because we are obligated to respond to this false assertion. Punishment expresses the moral truth that victim and wrongdoer are equally valuable. We argue that Hampton's argument would work only if she held (...) that exerting power over another provides evidence (albeit defeasible) of one's greater value. This is clearly a premise that neither she nor her readers are likely to accept. (shrink)

Paul Pietroski has developed a powerful minimalist and internalist alternative to standard compositional semantics, where meanings are identified with instructions to fetch or assemble human concepts in specific ways. In particular, there appears to be no need for Fregean Function Application, as natural language composition only involves processes of combining monadic or dyadic concepts, and Pietroski’s theory can then, allegedly, avoid both singular reference and truth conditions. He also has a negative agenda, purporting to show, roughly, that the vocabulary of (...) standard truth conditional semantics is far too powerful to plausibly describe the linguistic competence of mere human minds. In this paper, I explain some of the basics of Pietroski’s compositional semantics and argue that his major objection to standard compositionality is inconclusive, because a similar argument can be mounted against his own minimalist theory. I argue that we need a clear distinction between the language of the theorist---theoretical notation---and the language whose nature we are trying to explain. The theoretical notation should in fact be as expressively powerful as possible. It does not follow that the notation cannot be used to explain mere human linguistic competence, even if human minds are limited in various ways. (shrink)

We examine the expressive power of probabilistic context free grammars (PCFGs), with a special focus on the use of probabilities as a mechanism for reducing ambiguity by filtering out unwanted parses. Probabilities in PCFGs induce an ordering relation among the set of trees that yield a given input sentence. PCFG parsers return the trees bearing the maximum probability for a given sentence, discarding all other possible trees. This mechanism is naturally viewed as a way of defining a new (...) class of tree languages. We formalize the tree language thus defined, study its expressive power, and show that the latter is beyond context freeness. While the increased expressive power offered by PCFGs helps to reduce ambiguity, we show that, in general, it cannot be decided whether a PCFG removes all ambiguities. (shrink)

We examine the expressive power of probabilistic context free grammars (PCFGs), with a special focus on the use of probabilities as a mechanism for reducing ambiguity by filtering out unwanted parses. Probabilities in PCFGs induce an ordering relation among the set of trees that yield a given input sentence. PCFG parsers return the trees bearing the maximum probability for a given sentence, discarding all other possible trees. This mechanism is naturally viewed as a way of defining a new (...) class of tree languages. We formalize the tree language thus defined, study its expressive power, and show that the latter is beyond context freeness. While the increased expressive power offered by PCFGs helps to reduce ambiguity, we show that, in general, it cannot be decided whether a PCFG removes all ambiguities. (shrink)

There are many different ways to talk about the world. Some ways of talking are more expressive than others—that is, they enable us to say more things about the world. But what exactly does this mean? When is one language able to express more about the world than another? In my dissertation, I systematically investigate different ways of answering this question and develop a formal theory of expressive power, translation, and notational variance. In doing so, I show (...) how these investigations help to clarify the role that expressive power plays within debates in metaphysics, logic, and the philosophy of language. (shrink)

We introduce SO-HORNr which is a revised version of SO-HORN and show that SO-HORNr captures equation image on ordered finite structures. We also introduce second-order extended Horn logic SO-EHORN and a superclass SO-EHORNr of it. We show that both of them capture equation image on ordered finite structures by proving that SO-EHORN and SO-EHORNr have the same expressive power when only consider ordered structures.

In this article we study linear temporal logics with team semantics that are novel logics for defining hyperproperties. We define Kamp-type translations of these logics into fragments of first-order team logic and second-order logic. We also characterize the expressive power and the complexity of model-checking and satisfiability of team logic and second-order logic by relating them to second- and third-order arithmetic. Our results set in a larger context the recent results of Lück showing that the extension of TeamLTL (...) by the Boolean negation is highly undecidable under the so-called synchronous semantics. We also study stutter-invariant fragments of extensions of TeamLTL. (shrink)

We show how to encode context-free string grammars, linear context-free tree grammars, and linear context-free rewriting systems as Abstract Categorial Grammars. These three encodings share the same constructs, the only difference being the interpretation of the composition of the production rules. It is interpreted as a first-order operation in the case of context-free string grammars, as a second-order operation in the case of linear context-free tree grammars, and as a third-order operation in the case of linear context-free rewriting systems. This (...) suggest the possibility of defining an Abstract Categorial Hierarchy. (shrink)

We study definability in terms of monotone generalized quantifiers satisfying Isomorphism Closure, Conservativity and Extension. Among the quantifiers with the latter three properties - here called CE quantifiers - one finds the interpretations of determiner phrases in natural languages. The property of monotonicity is also linguistically ubiquitous, though some determiners like an even number of are highly non-monotone. They are nevertheless definable in terms of monotone CE quantifiers: we give a necessary and sufficient condition for such definability. We further identify (...) a stronger form of monotonicity, called smoothness, which also has linguistic relevance, and we extend our considerations to smooth quantifiers. The results lead us to propose two tentative universals concerning monotonicity and natural language quantification. The notions involved as well as our proofs are presented using a graphical representation of quantifiers in the so-called number triangle. (shrink)

We show how to encode context-free string grammars, linear context-free tree grammars, and linear context-free rewriting systems as Abstract Categorial Grammars. These three encodings share the same constructs, the only difference being the interpretation of the composition of the production rules. It is interpreted as a first-order operation in the case of context-free string grammars, as a second-order operation in the case of linear context-free tree grammars, and as a third-order operation in the case of linear context-free rewriting systems. This (...) suggest the possibility of defining an Abstract Categorial Hierarchy. (shrink)