Challenges and potential of the Semantic Web for tourism

The paper explores tourism challenges and potential of the Semantic Web from a theoretical and industry perspective. It first examines tourism business networks and explores a main theme of network interoperability - data standards- followed by technology deficiencies of Web 1.0 and 2.0 and Semantic Web solutions. It then explicates Semantic opportunities and challenges for tourism, including an industry perspective through a qualitative approach. Industry leaders considered that the new Web era was imminent and heralded benefits for supply and demand side interoperability, although management and technical challenges could impede progress and delay realisation

Continuous Queries and Real-time Analysis of Social Semantic Data with C-SPARQL

Abstract. Social semantic data are becoming a reality, but apparently their streaming nature has been ignored so far. Streams, being unbounded sequences of time-varying data elements, should not be treated as persistent data to be stored “forever ” and queried on demand, but rather as transient data to be consumed on the fly by queries which are registered once and for all and keep analyzing such streams, producing answers triggered by the streaming data and not by explicit invocation. In this paper, we propose an approach to continuous queries and realtime analysis of social semantic data with C-SPARQL, an extension of SPARQL for querying RDF streams

A Trichotomy for Regular Simple Path Queries on Graphs

Regular path queries (RPQs) select nodes connected by some path in a graph. The edge labels of such a path have to form a word that matches a given regular expression. We investigate the evaluation of RPQs with an additional constraint that prevents multiple traversals of the same nodes. Those regular simple path queries (RSPQs) find several applications in practice, yet they quickly become intractable, even for basic languages such as (aa)* or a*ba*. In this paper, we establish a comprehensive classification of regular languages with respect to the complexity of the corresponding regular simple path query problem. More precisely, we identify the fragment that is maximal in the following sense: regular simple path queries can be evaluated in polynomial time for every regular language L that belongs to this fragment and evaluation is NP-complete for languages outside this fragment. We thus fully characterize the frontier between tractability and intractability for RSPQs, and we refine our results to show the following trichotomy: Evaluations of RSPQs is either AC0, NL-complete or NP-complete in data complexity, depending on the regular language L. The fragment identified also admits a simple characterization in terms of regular expressions. Finally, we also discuss the complexity of the following decision problem: decide, given a language L, whether finding a regular simple path for L is tractable. We consider several alternative representations of L: DFAs, NFAs or regular expressions, and prove that this problem is NL-complete for the first representation and PSPACE-complete for the other two. As a conclusion we extend our results from edge-labeled graphs to vertex-labeled graphs and vertex-edge labeled graphs.Comment: 15 pages, conference submissio

Nesting Depth of Operators in Graph Database Queries: Expressiveness Vs. Evaluation Complexity

Designing query languages for graph structured data is an active field of research, where expressiveness and efficient algorithms for query evaluation are conflicting goals. To better handle dynamically changing data, recent work has been done on designing query languages that can compare values stored in the graph database, without hard coding the values in the query. The main idea is to allow variables in the query and bind the variables to values when evaluating the query. For query languages that bind variables only once, query evaluation is usually NP-complete. There are query languages that allow binding inside the scope of Kleene star operators, which can themselves be in the scope of bindings and so on. Uncontrolled nesting of binding and iteration within one another results in query evaluation being PSPACE-complete. We define a way to syntactically control the nesting depth of iterated bindings, and study how this affects expressiveness and efficiency of query evaluation. The result is an infinite, syntactically defined hierarchy of expressions. We prove that the corresponding language hierarchy is strict. Given an expression in the hierarchy, we prove that it is undecidable to check if there is a language equivalent expression at lower levels. We prove that evaluating a query based on an expression at level i can be done in $\Sigma_i$ in the polynomial time hierarchy. Satisfiability of quantified Boolean formulas can be reduced to query evaluation; we study the relationship between alternations in Boolean quantifiers and the depth of nesting of iterated bindings.Comment: Improvements from ICALP 2016 review comment

Модель уведомлений для разработки программных приложений интеллектуальных пространств

We consider a notification model for constructing interactions of multiple software agents in a smart space. The model supports Smart-M3 application development and exploits such features as subscription operation and ontological information representation. The set of required variants for interaction is described using a notification ontology, which extends the application domain ontology. Programming the interaction is reduced to subscription that each agent implements based on the notification ontology. The applicability of model is demonstrated on the case study of SmartScribo system for smart space multi-blogging. Our experiments show reasonable performance for this class of applications.Рассматривается модель уведомлений для организации взаимодействия множества программных агентов в интеллектуальном пространстве. Модель предназначена для проблемно-ориентированной разработки программных приложений на платформе Smart-M3, используя такие возможности, как операция подписки и онтологическое представление информации. Набор требуемых вариантов взаимодействия описывается на основе онтологии уведомлений, расширяющей исходную онтологию предметной области приложения. Реализация взаимодействия сводится к выполнению каждым агентом подписки на нужные варианты взаимодействия из онтологии уведомлений. Применимость модели показана на примере программной системы SmartScribo, реализующей интеллектуальное пространство для мультиблоггинга. Выполненный экспериментальный анализ показывает приемлемую для таких приложений производительность

Semantic Approach for Discovery and Visualization of Academic Information Structured with OAI-PMH

There are different channels to communicate the results of a scientific research; however, several research communities state that the Open Access (OA) is the future of acad emic publishing. These Open Ac cess Platforms have adopted OAI - PMH (Open Archives Initiative - the Protocol for Metadata Harvesting) as a standard for communication and interoperability. Nevertheless, it is significant to highlight that the open source know ledge discovery services based on an index of OA have not been developed. Therefore, it is necessary to address Knowledge Discovery (KD) within these platforms aiming at studen ts, teachers and/ or researchers , to recover both , the resources requested and th e resources that are not explicitly requested – which are also appropriate . This objective represents an important issue fo r structured resources under OAI - PMH. This fact is caused because interoperability with other developments carried out outside their implementation environment is generally not a priority (Level 1 "Shared term definitions"). It is here , where the Semantic Web (SW) beco mes a cornerstone of this work. Consequently, we propose OntoOAIV, a semantic approach for the selective knowledge disco very an d visu alization into structured information with OAI - PMH, focused on supporting the activities of scientific or academic research for a specific user. Because of the academic nature of the structured resources with OAI - PMH, the field of application chosen is the context information of a student. Finally, in order to validate the proposed approach, we use the RUDAR (Roskilde University Digital Archive) and REDALYC (Red de Revistas Científicas de América Latina y el Caribe, España y Portugal) repositor ies, which imple ment the OAI - PMH protocol , as well as one s tudent profile for carrying out KD