The complexity of concept languages

The basic feature of Terminological Knowledge Representation Systems is to represent knowledge by means of taxonomies, here called terminologiesand to provide a specialized reasoning engine to do inferences on these structures. The taxonomy is built through a representation language called concept language (or description logic), which is given well-defined set-theoretic semantics. The efficiency of reasoning has often been advocated as a primary motivation for the use of such systems. Deduction methods and computational properties of reasoning problems in concept languages are the subject of this paper. The main contributions of the paper are: (1) a complexity analysis of concept satisfiability and subsumption for a wide class of concept languages; (2) the algorithms for these inferences that comply with the worst-case complexity of the reasoning task they perform

A refined architecture for terminological systems : terminology = schema + views

Traditionally, the core of a Terminological Knowledge Representation System (TKRS) consists of a TBox, where concepts are introduced, and an ABox, where facts about individuals are stated in terms of concept memberships. This design has a drawback because in most applications the TBox has to meet two functions at a time: On the one hand - similarly to a database schema - frame-like structures with type information are introduced through primitive concepts and primitive roles; on the other hand, views on the objects in the knowledge base are provided through defined concepts. We propose to account for this conceptual separation by partitioning the TBox into two components for primitive and defined concepts, which we call the schema and the view part.We envision the two parts to differ with respect to the language for concepts, the statements allowed, and the semantics. We argue that this separation achieves more conceptual clarity about the role of primitive and defined concepts and the semantics of terminological cycles. Three case studies show the computational benefits to be gained from the refined architecture

Automatic Support for Verification of Secure Transactions in Distributed Environment using Symbolic Model Checking

Electronic commerce needs the aid of software tools to check the validity of business processes in order to fully automate the exchange of information through the network. Symbolic model checking has been used to formally verify specifications of secure transactions in a system for business-to-business applications. The fundamental principles behind symbolic model checking are presented along with techniques used to model mutual exclusion of processes and atomic transactions. The computational resources required to check the example process are presented, and the faults are detected through symbolic verification

Queries, rules and definitions as epistemic statements in concept languages

Concept languages have been studied in order to give a formal account of the basic features of frame-based languages. The focus of research in concept languages was initially on the semantical reconstruction of frame-based systems and the computational complexity of reasoning. More recently, attention has been paid to the formalization of other aspects of frame-based languages, such as non-monotonic reasoning and procedural rules, which are necessary in order to bring concept languages closer to implemented systems. In this paper we discuss the above issues in the framework of concept languages enriched with an epistemic operator. In particular, we show that the epistemic operator both introduces novel features in the language, such as sophisticated query formulation and closed world reasoning, and makes it possible to provide a formal account for some aspects of the existing systems, such as rules and definitions, that cannot be characterized in a standard first-order framework

The complexity of existential quantification in concept languages

Much of the research on concept languages, also called terminological languages, has focused on the computational complexity of subsumption. The intractability results can be divided into two groups. First, it has been shown that extending the basic language FL- with constructs containing some form of logical disjunction leads to co-NP-hard subsumption problems. Second, adding negation to FL- makes subsumption PSPACE-complete. The main result of this paper is that extending FL- with unrestricted existential quantification makes subsumption NP-complete. This is the first proof of intractability for a concept language containing no construct expressing disjunction--whether explicitly or implicitly. Unrestricted existential quantification is therefore, alongside disjunction, a source of computational complexity in concept languages

Nutrizione e ritmo circadiano: la nuova prospettiva del Time Restricted Feeding

SommarioNegli ultimi anni il digiuno intermittente è emerso quale approccio innovativo per promuovere il calo ponderale e migliorare lo stato di salute metabolica in contrapposizione agli interventi più convenzionali incentrati sulla restrizione calorica. Il digiuno intermittente (Intermittent Fasting) e il Time-Restricted Feeding (TRF) negli animali (anche noto come Time-Restricted Eating, TRE nell'uomo) hanno raggiunto una crescente popolarità parallelamente al consistente aumento delle evidenze scientifiche nell'ambito della cronobiologia, con la recente attribuzione del premio Nobel per la Medicina nel 2017 a Jeffrey C. Hall, Michael Rosbash e Michael W. Young quale riconoscimento per il contributo alle scoperte dei meccanismi molecolari che sottendono il ritmo circadiano. Il sistema circadiano regola il metabolismo in un ciclo di circa ventiquattro ore, determinando una ritmicità circadiana endogena nel dispendio energetico, nell'appetito, nella sensibilità insulinica e in altri processi metabolici. Molti di tali processi, tra cui la sensibilità insulinica e la termogenesi indotta dalla dieta, presentano un picco nella prima parte della giornata. Numerose evidenze sia nell'animale sia nell'uomo sottolineano che alimentarsi in momenti della giornata che siano asincroni rispetto ai ritmi delle suddette funzioni metaboliche promuova l'eccesso ponderale e le alterazioni metaboliche ad esso associate

L'assorbimetria a raggi X a doppia energia: oltre l'osso c'è di più

SommarioAlla base dell'attuale epidemia di obesità (globesity) la sedentarietà occupa un posto di primo ordine: non solo perché mantiene l'eccesso di tessuto adiposo, ma perché predispone il soggetto obeso all'erosione della massa muscolare scheletrica (sarcopenia) e del patrimonio minerale osseo (osteopenia/osteoporosi). In questo scenario si inserisce la DXA che, a fronte di un costo biologico e tempi di esecuzione minimi, nella versione total-body fornisce una fotografia attendibile e dettagliata della composizione corporea (si pensi alla massa magra appendicolare o al tessuto adiposo viscerale). Dettagli che però sono essenziali proprio per le diagnosi di sarcopenia e obesità

The complexity of concept languages

The basic feature of Terminological Knowledge Representation Systems is to represent knowledge by means of taxonomies, here called terminologies , and to provide a specialized reasoning engine to do inferences on these structures. The taxonomy is built through a representation language called concept language (or description logic), which is given well-defined set-theoretic semantics. The efficiency of reasoning has often been advocated as a primary motivation for the use of such systems. Deduction methods and computational properties of reasoning problems in concept languages are the subject of this paper. The main contributions of the paper are: (1) a complexity analysis of concept satisfiability and subsumption for a wide class of concept languages; (2) the algorithms for these inferences that comply with the worst-case complexity of the reasoning task they perform

Description Logics Approach to Semantic Matching of Web Services

As more resources and services become available on the Web, there is a growing need for infrastructures that, based on advertised descriptions, semantically match in a peer-to-peer way providers with requesters of web services. We address the problem of matchmaking of web services from a knowledge representation perspective. Based on our approach we propose match categorization in terms of exact match, potential match – when request and offer though not identical are compatible – and partial match – when one or more inconsistency is present – and rank of matches within categories. Then we report on our implementation of the proposed matchmaking framework in a prototype system

Ultrafast photochromism and bacteriochromism in one dimensional hybrid plasmonic photonic structures

Hybrid plasmonic photonic structures combine the plasmonic response with the photonic band gap, holding promise for utilization as optical switches and sensors. Here, we demonstrate the active modulation of the optical response in such structures with two different external stimuli, e.g. laser pulses and bacteria. First, we report the fabrication of a miniaturized (5 x 5 mm) indium tin oxide (ITO) grating employing femtosecond laser micromachining, and we show the possibility to modulate the photonic band gap in the visible via ultrafast photoexcitation in the infrared part of the spectrum. Note that the demonstrated time response in the picosecond range of the spectral modulation have an industrial relevance. Moreover, we manufacture one-dimensional photonic crystals consisting of a solution-processed dielectric Bragg stack exposing a top-layer of bio-active silver. We assign the bacterial responsivity of the system to polarization charges at the Ag/bacterium interface, giving rise to an overall blue shift of the photonic band gap.Comment: 7 pages, 4 figure