다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

An Introduction to MultiAgent Systems.

https://www.cs.ox.ac.uk/people/bernardo.cuencagrau/publications/PelletDemo.pdf

Pellet: A practical OWL-DL reasoner

Data integration is the problem of combining data residing at different sources, and providing the user with a unified view of these data. The problem of designing data integration systems is important in current real world applications, and is characterized by a number of issues that are interesting from a theoretical point of view. This document presents on overview of the material to be presented in a tutorial on data integration. The tutorial is focused on some of the theoretical issues that are relevant for data integration. Special attention will be devoted to the following aspects: modeling a data integration application, processing queries in data integration, dealing with inconsistent data sources, and reasoning on queries.

/pdf/data-integration-a-theoretical-perspective-58aesjvhuk.pdf

Data integration: a theoretical perspective

Description Logics (DLs) are used in Artificial Intelligence to represent knowledge in terms of objects grouped into classes, and offer structuring mechanisms for both characterizing the relevant properties of classes in terms of binary relations, and establishing several interdependencies among classes. One of the main themes in the area of DLs has been to identify DLs that are both very expressive and decidable. This issue can be profitably addressed by relying on a correspondence between DLs and propositional dynamic logics (PDLs). In this paper, we exploit the correspondence as a framework to investigate the decidability and the complexity of a powerful DL, in which functional restrictions on both atomic roles and their inverse are expressible. We then show that such DL is suitable to represent n-ary relations, as needed in the applications of class-based formalisms to databases. The PDL that we use in this work is a proper extension of Converse Deterministic PDL, and its decidability and complexity is established contextually.

/pdf/description-logics-with-inverse-roles-functional-l2rt3fyjsr.pdf

Description Logics with Inverse Roles, Functional Restrictions, and N-ary Relations

View-based query processing requires to answer a query posed to a database only on the basis of the information on a set of views, which are again queries over the same database. This problem is relevant in many aspects of database management, and has been addressed by means of two basic approaches, namely, query rewriting and query answering. In the former approach, one tries to compute a rewriting of the query in terms of the views, whereas in the latter, one aims at directly answering the query based on the view extensions. Based on recent results, we first show that already for very simple query languages, a rewriting is in general a co-NP function wrt to the size of view extensions. Hence, the problem arises of characterizing which instances of the problem admit a rewriting that is PTIME. However, a tight connection between view-based query answering and constraint-satisfaction problems, allows us to show that the above characterization is going to be difficult.

What is Query Rewriting

One of the outcomes of the research work carried out on data integration in the last years is a clear architecture, comprising a global schema, the source schema and the mapping between the source and the global schema. In this chapter, we study data integration under this framework when the global schema is specified in OWL, the standard language for the Semantic Web and discuss the impact of this choice on computational complexity of query answering under different instantiations of the framework in terms of query language and form and interpretation of the mapping. We show that query answering in the resulting setting is computationally too complex, and discuss in detail the various sources of complexity. Then, we show how to limit the expressive power of the various components of the framework in order to have efficient query answering, in principle as efficient as query processing in relational DBMSs. In particular, we adopt OWL 2 QL as the ontology language used to express the global schema. OWL 2 QL is one of the tractable profiles of OWL 2, and essentially corresponds to a member of the DL-Lite family, a family of Description Logics designed to have a good trade-off between expressive power of the language and computational complexity of reasoning.

/pdf/using-owl-in-data-integration-4xx8y8hfmi.pdf

Using OWL in Data Integration

Composition of e-Services is the issue of synthesizing a new composite e-Service, obtained by combining a set of available component e-Services, when a client request cannot be satisfied by available e-Services. In this paper we study the problem of composition synthesis in a general framework. We consider e-Services as arbitrary (possibly infinite) execution trees, i.e., as trees of all potential interactions with clients, and characterize composition in this abstract setting. We then show how this setting can be realized using Reasoning About Actions, in particular reasoning in Situation Calculus, and exploiting a correspondence with Deterministic Propositional Dynamic Logic, we provide automated procedures and complexity results for performing composition.

Reasoning about actions for e-service composition

We aim at representing and reasoning about actions and (high level) programs over ontologies expressed in Description Logics. This is a critical issue that has resisted good solutions for a long time. In particular, while welldeveloped theories of actions and high-level programs exist in AI, e.g., the ones based on SitCalc, these theories do not apply smoothly to Description Logic ontologies, due to the profoundly non-definitorial nature of such ontologies (cf. cyclic TBoxes). Here we propose a radical solution: we assume a functional view of ontologies and see them as systems that allow for two kinds of operations: ASK, which returns the (certain) answer to a query, and TELL, which produces a new ontology as a result of the application of an atomic action. We base atomic actions on instance level update and instance level erasure on the ontology. Building on this functional view, we introduce Golog/ConGolog-like high-level programs on ontologies. This paper demonstrates the effectiveness of the approach in general, and presents the following specific results: we characterize the notion of single-step executability of such programs, devise methods for reasoning about sequences of actions, and present (nice) complexity results in the case where the ontology is expressed in DL-Lite.

/pdf/actions-and-programs-over-description-logic-ontologies-4b2hz4v5ka.pdf

Giuseppe De Giacomo

Papers

Description Logics with Inverse Roles, Functional Restrictions, and N-ary Relations

What is Query Rewriting

Using OWL in Data Integration

Reasoning about actions for e-service composition

Actions and programs over description logic ontologies