Mogens Nielsen

Petri nets, event structures and domains, part I

Abstract The general aim of this paper is to find a theory of concurrency combining the approaches of Petri and Scott (and others). In part I we introduce our formalisms. To connect the abstract ideas of events and domains of information, we show how casual nets induce certain kinds of domains where the information points are certain sets of events. This allows translations between the languages of net theory and domain theory. Following the idea that events of causal nets are occurrences, we generalise causal nets to occurrence nets, by adding forwards conflict. Just as infinite flow charts unfold finite ones, so transition nets can be unfolded into occurrence nets. Next we extend the above connections between nets and domains to these new nets. Event structures which are intermediate between nets and domains play an important part in all our work. Finally, as an example of how concepts translate from one formalism to the other, we show how Petris notion of confusion ties up with Kahn and Plotkins concrete domains. In part II we shall continue the job of connecting up notions within net theory and the theory of domains. In particular, we shall examine the idea of states of computations.

Petri Nets, Event Structures and Domains

The general aim of the paper is to find a theory of concurrency combining the approaches of Petri and Scott (and other workers) [Pet 1,2],ESeo ~,3],[Sto]. To connect the abstract ideas of events and domains of information, we show how causal nets induce certain kinds of domains where the information points are certain sets of events. This allows translations between the languages of net theory and domain theory. Following the idea that events of causal nets are occurrences we generalise causal nets to occurrence nets, by adding forwards conflict; just as infinite flow chartsunfold finite ones [Sco 2], so transition nets can be unfolded into occurrence nets. Next we extend the above connections between nets and domains to these new nets. Event structures, which are intermediate between nets and domains play an important part in all our work.

Bisimulation from Open Maps

An abstract definition of bisimulation is presented. It makes possible a uniform definition of bisimulation across a range of different models for parallel computation presented as categories. As examples, transition systems, synchronisation trees, transition systems with independence (an abstraction from Petri nets), and labelled event structures are considered. On transition systems the abstract definition readily specialises to Milners strong bisimulation. On event structures it explains and leads to a strengthening of the history-preserving bisimulation of Rabinovitch and Traktenbrot and van Glabeek and Goltz. A tie-up with open maps in a (pre)topos, as they appear in the work of Joyal and Moerdijk, brings to light a new model, presheaves on categories of pomsets, into which the usual category of labelled event structures embeds fully and faithfully. As an indication of its promise, this new presheaf model has “refinement” operators. The general approach yields a logic, generalising Hennessy?Milner logic, which is characteristic for the generalised notion of bisimulation.

ENERGETIC COSTS OF SIZE AND SEXUAL SIGNALLING IN A WOLF SPIDER

A prerequisite for honest handicaps is that there are significant condition–dependent costs in the expression of sexual traits. In the wolf spider Hygrolycosa rubrofasciata (Ohlert), sexual signalling (drumming) is costly in terms of increased mortality. Here we investigated whether this mortality may be caused by increased energy expenditure. During sexual signalling, metabolic rate was 22 times higher than at rest and four times higher than when males were actively moving. Metabolic rate per unit mass was positively related to absolute body mass during sexual signalling but not during other activities. This positive relationship is novel to any studies of metabolic rates. Indeed, it seems that the largest males can drum only 12 times per minute before reaching the maximum sustainable metabolic rate, whereas the smallest males may drum up to 39 times per minute. However, there is no relationship between body mass and drumming rate, indicating that larger males are able to compensate for the higher cost of drumming. There was a quadratic relationship between relative abdomen mass and overall body mass, which may provide a partial explanation for the increased energy expenditure of largest males while drumming. Altogether, our results indicate that sexual signalling is highly energetically demanding, which may be the main reason for the honesty of signalling in this species. In addition, the energetic costs are surprisingly strongly size dependent, which may compensate any disadvantage of small male size.

A formal model for trust in dynamic networks

We propose a formal model of trust informed by the Global Computing scenario and focusing on the aspects of trust formation, evolution, and propagation. The model is based on a novel notion of trust structures which, building on concepts from trust management and domain theory, feature at the same time a trust and an information partial order.

Experimental evidence for the costs and hygienic significance of the antibiotic metapleural gland secretion in leaf-cutting ants

Abstract. The paired exocrine metapleural glands present in the large majority of ant species produce compounds with antibiotic properties. In the leaf-cutting ant, Acromyrmex octospinosus, the secretion consists of more than 20 different compounds and it has generally been assumed that the glands serve as a general defence against various infectious microbes of fungal and bacterial origin. We present results illuminating the direct costs and benefits of these metapleural gland defences in A. octospinosus. We show that major workers of this leaf-cutting ant experience a significant reduction in their respiration rate when the metapleural glands are experimentally closed, indicating that metapleural gland secretion incurs a substantial cost and that the production of compounds from these glands is terminated when the ants are incapable of secreting them. In another set of experiments, we show that the ability to secrete antibiotic compounds from the metapleural glands is of significant importance when ants are exposed to a general but potentially virulent insect pathogen, Metarhizium anisopliae. Infection with this fungus is lethal within a few days when ants have their metapleural glands experimentally closed, but relatively harmless when the metapleural glands are functional. These findings support experimentally the view that the metapleural glands play an important hygienic role in leaf-cutting ants.

TAPSOFT '95: Theory and Practice of Software Development

A decade of TAPSOFT.- Theory and practice of software development.- Rational spaces and set constraints.- Formal methods and social context in software development.- Testing can be formal, too.- Anatomy of the Pentium bug.- Rational mechanics and natural mathematics.- First-order logic on finite trees.- Decidability of equivalence for deterministic synchronized tree automata.- The equivalence problem for letter-to-letter bottom-up tree transducers is solvable.- ?I: A symmetric calculus based on internal mobility.- Complete inference systems for weak bisimulation equivalences in the ?-calculus.- Reasoning about higher-order processes.- Confluence of processes and systems of objects.- An algebraic approach to temporal logic.- On behavioural abstraction and behavioural satisfaction in higher-order logic.- Assumption/guarantee specifications in linear-time temporal logic (extended abstract).- Fine hierarchy of regular ?-languages.- Computing the Wadge degree, the Lifschitz degree, and the Rabin index of a regular language of infinite words in polynomial time.- Semi-trace morphisms and rational transductions.- Nonfinite axiomatizability of shuffle inequalities.- On the category of Petri net computations.- High undecidability of weak bisimilarity for Petri nets.- Polynomial algorithms for the synthesis of bounded nets.- Semi-completeness of hierarchical and super-hierarchical combinations of term rewriting systems.- Lazy narrowing: Strong completeness and eager variable elimination (extended abstract).- On the expressive power of algebraic graph grammars with application conditions.- Generated models and the ?-rule: The nondeterministic case.- CPO models for a class of GSOS languages.- Statecharts, transition structures and transformations.- An imperative object calculus.- A refinement of import/export declarations in modular logic programming and its semantics.- Strictness and totality analysis with conjunction.- Generic techniques for source-level debugging and dynamic program slicing.- Reasoning with executable specifications.- Calculating software generators from solution specifications.- Comparing flow-based binding-time analyses.- Can you trust your data.- Static and dynamic processor allocation for higher-order concurrent languages.- Mechanized inductive proof of properties of a simple code optimizer.- Describing a Signal Analyzer in the process algebra PMC - A case study.- A gentle introduction to specification engineering using a case study in telecommunications.- Precise interprocedural dataflow analysis with applications to constant propagation.- Formal specification and prototyping of a program specializer.- Proving the correctness of recursion-based automatic program transformations.- Reactive system specification and refinement.- Measuring concurrency of regular distributed computations.- Non-speculative and upward invocation of continuations in a parallel language.- A model inference system for generic specification with application to code sharing.- Relations as abstract datatypes: An institution to specify relations between algebras.- Performance-oriented formal specifications - the LotoTis approach.- Signal: A formal design environment for real-time systems.- The META-Frame: An environment for flexible tool management.- STeP: The Stanford Temporal Prover.- The HOL-UNITY verification system.- PLATO: A tool to assist programming as term rewriting and theorem proving.- LOFT: A tool for assisting selection of test data sets from algebraic specifications.- The SMoLCS ToolSet.- The Asf+Sdf Meta-environment documentation tools for free.- The B-Toolkit demonstration.- Object Oriented Semantics Directed Compiler Generation: A prototype.

Mathematical Foundations of Computer Science 2000

Data Types in Computer Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 James H. Davenport What Do We Learn from Experimental Algorithmics? . . . . . . . . . . . . . . . . . . 36 Camil Demetrescu and Giuseppe F. Italiano And/Or Hierarchies and Round Abstraction . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Radu Grosu Computational Politics: Electoral Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Edith Hemaspaandra and Lane A. Hemaspaandra 0-1 Laws for Fragments of Existential Second-Order Logic: A Survey . . . . . 84 Phokion G. Kolaitis and Moshe Y. Vardi On Algorithms and Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Jan van Leeuwen and Jiř́ı Wiedermann On the Use of Duality and Geometry in Layouts for ATM Networks . . . . . . 114 Shmuel Zaks

SOFSEM 2009: Theory and Practice of Computer Science

SOFSEM 2009: Theory and Practice of Computer Science: 35th Conference on Current Trends in Theory and Practice of Computer Science : Spindlerův Mlýn, Czech Republic, January 2009, Proceedings of the Conference

Models for concurrency: towards a classification

Models for concurrency can be classified with respect to three relevant parameters: behaviour/ system, interleaving/noninterleaving, linear/branching time. When modelling a process, a choice concerning such parameters corresponds to choosing the level of abstraction of the resulting semantics. In this paper, we move a step towards a classification of models for concurrency based on the parameters above. Formally, we choose a representative of any of the eight classes of models obtained by varying the three parameters, and we study the formal relationships between them using the language of category theory.