Massimo Marchiori

University of Padova | UNIPD · Department of Mathematics

Background: Without proven effect treatments and vaccines, Social Distancing is the key protection factor against COVID-19. Social distancing alone should have been enough to protect again the virus, yet things have gone very differently, with a big mismatch between theory and practice. What are the reasons? A big problem is that there is no actual...

The main goal of this article is to investigate techniques that can quickly lead to successful social systems by boosting network connectivity. This is especially useful when starting new online communities where the aim is to increase the system utilization as much as possible. This aspect is very important nowadays, given the existence of many on...

Soccer is the most popular sport in the world, with currently over three billion fans. There are various reasons for this success, but a unique feature of soccer stands out: every match has a high level of unpredictability. For instance, it is not uncommon for a less skilled team to sometimes defeat a better team. Moreover, a match that is apparent...

Security and privacy of mobile users is a theme of primary importance, given the widespread and growing use of connected smartphones, the great amount of personal data that can leak, and the lack of proper controlled environments in the current mobile scenario (for instance, mobile apps and their handling of permissions). In this paper we focus on...

Big data and cloud systems are two crucial components of modern computing, but they are also a challenge to learn, as they change the basic assumptions of computing, and as such the mental habits that are proper of classical computing teaching. In other words, beyond a technical revolution, we first and foremost are in the presence of a mental revo...

Complex systems have attracted considerable interest because of their wide range of appli-cations, and are often studied via a " classic " approach: study a specific system, find a com-plex network behind it, and analyze the corresponding properties. This simple methodology has produced a great deal of interesting results, but relies on an often im...

Network analysis has emerged as a powerful approach to understand complex phenomena and organization in social, technological and biological systems. In particular, it is increasingly recognized the role played by the topology of cellular networks, the intricate web of interactions among genes, proteins and other molecules regulating cell activity,...

WWV’09 provided a common forum for researchers from the communities of Rule-based programming, Automated Software Engineering, and Web-oriented research, in order to facilitate the cross-fertilization and the advancement of hybrid methods that combine the three areas. The Program Committee of WWV’09 collected three reviews for each paper and held a...

The World Wide Web is nowadays the most famous and widespread information system. Its success is witnessed by its enormous size and rate of growth: however, the same success of the Web has brought to a situation where more sophisticated techniques are urgently needed to properly handle this mass of information. In this sense, the more ambitious pla...

This articles discusses rule languages that are needed for a a full deployment of the Semantic Web. First, it motivates the need for such languages. Then, it presents ten theses addressing (1) the rule and/or logic languages needed on the Web, (2) data and data processing, (3) semantics, and (4) engineering and rendering issues. Finally, it discuss...

The web landscape has undergone massive changes in the past years. On the other hand, search engine technology has not quite kept the same pace. In this article we look at the current scenarios, and argue how social flows can be used to make up for a better generation of search engines. We consider how society and technological progress somehow cha...

We introduce delta centralities, a new class of measures of structural centrality for networks. In particular, we focus on a measure in this class, the information centrality CI, which is based on the concept of efficient propagation of information over the network. CI is defined for both valued and non-valued graphs, and applies to groups as well...

The Web of the future will without doubts be very different from what we have nowadays. In this paper, we try to give a very high-level overview of the main aspects that will forge the new Web, having a look at five main S's: search, share, social, semantics, and the glue component that can keep them together, and let the user digest the new shifts...

In this paper we address the open problem of classifying the expressive power of classes of rewriting systems. We introduce a framework to reason about the relative expressive power between classes of rewrite system, with respect to every property of interest P. In particular, we investigate four main classes of rewriting systems: left-linear Term...

The Semantic Web has managed to produce an enormous buzzword. However, despite it cannot be considered a new technology anymore, it didn’t fly off yet, and has remained unexpressed in its potentials. In this article we try to analyze the possible reasons, and also the tension that the Semantic Web has with XML. We emphasize the need for considerati...

The basic notion of encoding is one of the most important present in computer science. So far, they have not been per se the subject of serious research, because of their apparent simplicity. In this paper we show how the realm of encodings, instead, deserves big attention. In particular, we address the fundamental question of optimality of encodin...

This paper introduces an alternative operational model for constraint logic programs. First, a transition system is introduced, which is used to define a trace semantics T. Next, an equivalent fixpoint semantics F is defined: a dataflow graph is assigned to a program, and a consequence operator on tuples of sets of constraints is given whose least...

The most important open problem in the study of termination for logic programs is that of existential termination. In this paper we present a powerful transformational methodology that provides necessary (and, under some conditions, sufficient) criteria for existential termination. The followed approach is to develop a suitable transformation from...

This articles discusses the logic, or logic-based, languages required for a full deployment of the Semantic Web. It presents ten theses addressing 1 the kinds of logic languages needed, 2 data and data processing, 3 semantics, and 4 engineering and rendering issues. The views reported about in this article have been presented at the W3C Workshop on...

Infrastructure systems are a key ingredient of modern society. We discuss a general method to find the critical components of an infrastructure network, i.e., the nodes and the links fundamental to the perfect functioning of the network. Such nodes, and not the most connected ones, are the targets to protect from terrorist attacks. The method, used...

From 11.09.05 to 16.09.05, the Dagstuhl Seminar 05371 ``Principles and Practices of Semantic Web Reasoning'' % generate automaticall was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abst...

This article discusses forms of reasoning (beyond ontology reasoning), and reasoning languages (beyond ontology languages), that are needed for a full deployment of the Semantic Web. We first outline a motivating application scenario, then discuss the logic languages needed on the Semantic Web and related issues. The views reported about in this ar...

Community structures are an important feature of many social, biological, and technological networks. Here we study a variation on the method for detecting such communities proposed by Girvan and Newman and based on the idea of using centrality measures to define the community boundaries [M. Girvan and M. E. J. Newman, Proc. Natl. Acad. Sci. U.S.A....

This paper introduces Metalog, a query/logical system designed to allow reasoning on the Web. Metalog tries to start filling in the so-called people axis, where the Web is tailored for the people, and not just for the machine. Besides allowing the formulation of declarative logical rules, Metalog's distinctive feature is to lower the entry access l...

Motivation: Immune cells coordinate their efforts for the correct and efficient functioning of the immune system (IS). Each cell type plays a distinct role and communicates with other cell types through mediators such as cytokines, chemokines and hormones, among others, that are crucial for the functioning of the IS and its fine tuning. Neverthele...

Communication/transportation systems are often subjected to failures and attacks. Here we represent such systems as networks and we study their ability to resist failures (attacks) simulated as the breakdown of a group of nodes of the network chosen at random (chosen accordingly to degree or load). We consider and compare the results for two differ...

Large-scale blackouts are an intrinsic drawback of electric power transmission grids. Here we analyze the structural vulnerability of the Italian GRTN power grid by using a model for cascading failures recently proposed in Crucitti et al. (Phys. Rev. E 69 (2004)).

mputationally intractable). -- A "test property", # (that is usually computationally tractable). -- A "universe" of entities (e.g., software agents, persons, etc.). -- A number R (# [0, 1]), indicating the "real" probability that # implies . -- A mapping S from to [0, 1], indicating that the "subjective" probability for an entity e # U that # impli...

Large but rare cascades triggered by small initial shocks are present in most of the infrastructure networks. Here we present a simple model for cascading failures based on the dynamical redistribution of the flow on the network. We show that the breakdown of a single node is sufficient to collapse the efficiency of the entire system if the node is...

At the present time, the most commonly accepted definition of a complex system is that of a system containing many interdependent constituents which interact nonlinearly. Therefore, when we want to model a complex system, the first issue has to do with the connectivity properties of its network, the architecture of the wirings between the constitue...

A great variety of complex phenomena in many scientific fields exhibit power-law behavior, reflecting a hierarchical or fractal structure. Many of these phenomena seem to be susceptible to description using approaches drawn from thermodynamics or statistical mechanics, particularly approaches involving the maximization of entropy and of Boltzmann-G...

A new method, based on a recently defined centrality measure, allows to spot the critical components of a generic complex network. The identification and protection of the critical components of a given communication–transportation network should be the first concern in order to reduce the consequences of terrorist attacks. On the other hand, the c...

The World Wide Web is a Web of information. Information can be more or less qualified, more or less usable, more or less usable by automatic processors. Information of the most different kinds, that can be reused for a lot of purposes. So how do we treat this information, how do we give some order, and possibly help its intelligent reuse? Keywords...

We introduce a new measure of centrality, the information centrality C^I, based on the concept of efficient propagation of information over the network. C^I is defined for both valued and non-valued graphs, and applies to groups and classes as well as individuals. The new measure is illustrated and compared to the standard centrality measures by us...

How can Mathematics and the Semantic Web e#ectively join? In this paper we provide an account of the key standard technologies that can foster the integration of Mathematical representation into the Semantic Web.

The concept of network efficiency, recently proposed to characterize the properties of small-world networks, is here used to study the effects of errors and attacks on scale-free networks. Two different kinds of scale-free networks, i.e., networks with power law P(k), are considered: (1) scale-free networks with no local clustering produced by the...

The mathematical study of the small-world concept has fostered quite some interest, showing that small-world features can be identified for some abstract classes of networks. However, passing to real complex systems, as for instance transportation networks, shows a number of new problems that make current analysis impossible. In this paper we show...

A short review of the recent results and models of complex networks.

The small-world phenomenon has been already the subject of a huge variety of papers, showing its appeareance in a variety of systems. However, some big holes still remain to be filled, as the commonly adopted mathematical formulation suffers from a variety of limitations, that make it unsuitable to provide a general tool of analysis for real networ...

We introduce the concept of efficiency of a network as a measure of how efficiently it exchanges information. By using this simple measure, small-world networks are seen as systems that are both globally and locally efficient. This gives a clear physical meaning to the concept of "small world," and also a precise quantitative analysis of both weigh...

The small-world phenomenon, popularly known as six degrees of separation, has been mathematically formalized by Watts and Strogatz in a study of the topological properties of a network. Small-world networks are defined in terms of two quantities: they have a high clustering coefficient C like regular lattices and a short characteristic path length...

Conditional rewriting is universally recognized as being much more complicated than unconditional rewriting. In this paper we study how much of conditional rewriting can be automatically inferred from the simpler theory of unconditional rewriting. We introduce a new tool, called unraveling, to automatically translate a conditional term rewriting sy...

Machine (WAM), developed in [9] (however we will refer to the version presented by Ait-Kaci in his tutorial [1]). We show how, with some modifications both on the clause compilation scheme and on the instructions semantics, one can obtain an efficient and nice compiled code for these programs. In particular the following unpleasant WAM features dis...

. This paper introduces a necessary and sufficient condition for termination of constraint logic programs. The method is based on assigning a dataflow graph to a program, whose nodes are the program points and whose arcs are abstractions of the rules of a transition system, describing the operational behaviour of constraint logic programs. Then ter...

. This paper introduces an alternative operational model for constraint logic programs. First, a transition system is introduced, which is used to define a trace semantics T . Next, an equivalent fixpoint semantics F is defined: a dataflow graph is assigned to a program, and a consequence operator on tuples of sets of constraints is given whose lea...

In this paper we study the relationships between logic programming and functional programming, trying to answer the following basic question: to what extent is logic programming just functional programming in disguise? We develop a theory to formally express this correspondence, and exhibit a class that can by right be considered as the functional...

. One of the key results in the field of modularity for Term Rewriting Systems is the modularity of completeness for left-linear TRSs established by Toyama, Klop and Barendregt in [TKB89]. The proof, however, is quite long and involved. In this paper, a new proof of this basic result is given which is both short and easy, employing the powerful tec...

This paper studies the relationship between logic programs and term rewriting systems (TRSs). A compositional transform is defined which given a logic program computes a TRS. For a relevant class of logic programs, called Simply Well Moded (SWM), there is a one-to-one correspondence between computed answer substitutions of the logic program and nor...

Despite the major role that modularity occupies in computer science, all the known results on modular analysis only treat particular problems, and there is no general unifying theory. In this paper we provide such a general theory of modularity. First, we study the space of the criteria for modularity (the so-called modularity space), and give resu...

) 1 Introduction Two of the major paradigms that have had a great impetus in these last years are logic programming and functional programming. Both of these paradigms have intrinsic features that make them extremely elegant and expressive. On the one hand, logic programming retains the power of relational programming, where concepts are described...

In this paper it is performed a thorough theoretical study of unication free logic programs, that is programs in which unication can be replaced by (iterated) matching. We introduce a global framework to study unication freedom, based on the simple concept of matching direction. Furthermore, we develop some syntactical criterions to ensure a progra...

In many applications, such as decision support, negotiation, planning, scheduling, etc., one needs to express requirements that can only be partially satisfied. In order to express such requirements, we propose a technique called forward-tracking. Intuitively, forward-tracking is a kind of dual of chronological back-tracking: if a program globally...

The last open problem regarding the modularity of the fundamental properties of Term Rewriting Systems concerns the property of uniqueness of normal forms w.r.t. reduction (UN-->). In this article we solve this open problem, showing that UN--> is modular for left-linear Term Rewriting Systems. The novel ''pile and delete'' technique here introduced...

As all the recent market surveys witness, the World Wide Web (WWW) is expanding at a phenomenal rate, both in the number of users and in the amount of available information. This has made the World Wide Web one of the key fields for companies advertisement. On the other hand, advertisement on the web depends crucially on its visibility, i.e. on the...

For the majority of complex systems a satisfactory analysis is highly impractical, or even impossible at the current technological level. In this paper we employ a new methodology, called light analysis, to deal with such systems. Light analysis consists of extracting from a complex system a `light' version, which is structurally simpler. This way,...

The great potential of the World Wide Web is given by its capability of accessing information by navigating via hyper links from one site to another. However, this great potential is currently not properly fulfilled due to a rather poor connectivity, which makes navigation rather difficult and far from linear. This big problem is intrinsic to the w...

We propose a formalism for dynamic web sites, based on the RMM model, an existing methodology for the design of hypermedia applications. We provide an abstract de nition of its data and navigation model

The World Wide Web currently has a huge amount of data, with practically no classification information, and this makes it extremely difficult to handle effectively. It has been realized recently that the only feasible way to radically improve the situation is to add to Web objects a metadata classification, to help search engines and Web-based digi...

We provide a global technique, called neatening, for the study of modularity of left-linear term rewriting systems. Objects called bubbles are identified as the responsibles of most of the problems occurring in modularity, and the concept of well-behaved (from the modularity point of view) reduction, called neat reduction, is introduced. Neatening...

We propose a formalism for dynamic web sites, based on the RMM model, an existing methodology for the design of hypermedia applications. We provide an abstract de nition of its data and navigation model

This paper will demonstrate how a new querying language, Metalog, allows users to write inference rules andqueries in English-like syntax. We will demonstrate how these reasoning rules have equivalent representation bothas RDF descriptions and as logic programs. We will also show how an automated compilation between thesetranslations is possible.Fo...

The World Wide Web currently has a huge amount of data, with practically no classification information, and this makes it extremely difficult to handle effectively. It has been realized recently that the only feasible way to radically improve the situation is to add to Web objects a metadata classification, to help search engines and Web-based digi...

The paper is concerned with the integration of constraint logic programming systems (CLP) with systems based on genetic algorithms (GA). The resulting framework is tailored for applications that require a first phase in which a number of constraints need to be generated, and a second phase in which an optimal solution satisfying these constraints i...