Data Mining - Concepts and Techniques.

Data Mining Practical Machine Learning Tools and Techniques

Ontologies tend to be found everywhere. They are viewed as the silver bullet for many applications, such as database integration, peer-to-peer systems, e-commerce, semantic web services, or social networks. However, in open or evolving systems, such as the semantic web, different parties would, in general, adopt different ontologies. Thus, merely using ontologies, like using XML, does not reduce heterogeneity: it just raises heterogeneity problems to a higher level. Euzenat and Shvaikos book is devoted to ontology matching as a solution to the semantic heterogeneity problem faced by computer systems. Ontology matching aims at finding correspondences between semantically related entities of different ontologies. These correspondences may stand for equivalence as well as other relations, such as consequence, subsumption, or disjointness, between ontology entities. Many different matching solutions have been proposed so far from various viewpoints, e.g., databases, information systems, and artificial intelligence. The second edition of Ontology Matching has been thoroughly revised and updated to reflect the most recent advances in this quickly developing area, which resulted in more than 150 pages of new content. In particular, the book includes a new chapter dedicated to the methodology for performing ontology matching. It also covers emerging topics, such as data interlinking, ontology partitioning and pruning, context-based matching, matcher tuning, alignment debugging, and user involvement in matching, to mention a few. More than 100 state-of-the-art matching systems and frameworks were reviewed. With Ontology Matching, researchers and practitioners will find a reference book that presents currently available work in a uniform framework. In particular, the work and the techniques presented in this book can be equally applied to database schema matching, catalog integration, XML schema matching and other related problems. The objectives of the book include presenting (i) the state of the art and (ii) the latest research results in ontology matching by providing a systematic and detailed account of matching techniques and matching systems from theoretical, practical and application perspectives.

Ontology Matching

We explore the effect of dimensionality on the nearest neighbor problem. We show that under a broad set of conditions (much broader than independent and identically distributed dimensions), as dimensionality increases, the distance to the nearest data point approaches the distance to the farthest data point. To provide a practical perspective, we present empirical results on both real and synthetic data sets that demonstrate that this effect can occur for as few as 10-15 dimensions. These results should not be interpreted to mean that high-dimensional indexing is never meaningful; we illustrate this point by identifying some high-dimensional workloads for which this effect does not occur. However, our results do emphasize that the methodology used almost universally in the database literature to evaluate high-dimensional indexing techniques is flawed, and should be modified. In particular, most such techniques proposed in the literature are not evaluated versus simple linear scan, and are evaluated over workloads for which nearest neighbor is not meaningful. Often, even the reported experiments, when analyzed carefully, show that linear scan would outperform the techniques being proposed on the workloads studied in high (10-15) dimensionality!.

When is nearest neighbor meaningful

A super-peer is a node in a peer-to-peer network that operates both as a server to a set of clients, and as an equal in a network of super-peers. Super-peer networks strike a balance between the efficiency of centralized search, and the autonomy, load balancing and robustness to attacks provided by distributed search. Furthermore, they take advantage of the heterogeneity of capabilities (e.g., bandwidth, processing power) across peers, which recent studies have shown to be enormous. Hence, new and old P2P systems like KaZaA and Gnutella are adopting super-peers in their design. Despite their growing popularity, the behavior of super-peer networks is not well understood. For example, what are the potential drawbacks of super-peer networks? How can super-peers be made more reliable? How many clients should a super-peer take on to maximize efficiency? we examine super-peer networks in detail, gaming an understanding of their fundamental characteristics and performance tradeoffs. We also present practical guidelines and a general procedure for the design of an efficient super-peer network.

Designing an Super-Peer Network

Context-sensitive systems (CSS) are computer systems that use context to provide more relevant services or information to support users performing their tasks, where context is any information that can be used to characterize the situation in which something exists or occurs. CSS demand that designers consider new aspects and challenges in comparison to traditional applications. In a preliminary experiment, we observed that developers find it difficult to include the concept of context in their applications. However, only few approaches offer integrated domain-independent support on developing CSS. This paper presents an integrated approach to assist the design of CSS. The originality of this work lies on the proposed way of thinking about context, on the proposed context metamodel and on the specification of a process for designing CSS. The metamodel supports building context models by making explicit the concepts related to context manipulation and by separating the context structure model from the CSS behavior model. The design process details the main activities related to context specification and the design of CSS, providing a systematic way to execute these tasks. This work also advances the state of the art related to the understanding of the concept of context (and its associated concepts). Three experimental studies were conducted to evaluate the proposal: its instantiation in the design of a context-sensitive Expert Recommender System, its usage by distinct designers on their CSS projects, and a qualitative evaluation of the overall proposal by experienced CSS developers. These studies showed a good acceptance of our approach and indicated the feasibility of using it on real projects.

Designing context-sensitive systems: An integrated approach

XML has become the standard format for representing structured and semi-structured data on the Web. To describe the structure and content of XML data, several XML schema languages have been proposed. Although being very useful for validating XML documents, an XML schema is not suitable for tasks requiring knowledge about the semantics of the represented data. For such tasks it is better to use a conceptual schema. This paper presents an extension of the Entity Relationship (ER) model, called X-Entity, for conceptual modeling of XML schemas. We also present the process of converting a schema, defined in the XML Schema language, to an X-Entity schema. The conversion process is based on a set of rules that consider element declarations and type definitions and generates the corresponding conceptual elements. Such representation provides a cleaner description for XML schemas by focusing only on semantically relevant concepts. The X Entity model has been used in the context of a Web data integration system with the goal of providing a concise and semantic description for local schemas defined in XML Schema.

Conceptual modeling of XML schemas

A review is made of the most important decisions in the design of asynchronous systems to support the preparation of business decision meetings. These decisions are illustrated with the choices made for the development of SISCO, a system of this type. The presentation considers issues in the discussion model, the group memory, the communication and visualization mechanisms, and the development of a meeting preparation sequence: how to start a session, carry it out and close it. Issues concerning coordination, participation and awareness in meeting preparation sessions are also discussed.

Key issues in the design of an asynchronous system to support meeting preparation

An important issue in groupware is how to improve interaction and collaboration among participants. Through the analysis of the context a user is in or the context that surrounds an interaction, groupware systems can provide users with useful information in that situation. A relevant issue when using context is how to represent context information. Ontologies constitute an interesting method for representing context, since they enable information sharing and reuse. They can also be used by existing inference machines to reason about various contexts. In this paper we propose an ontology to formally represent context in groupware systems. We also present an example where this ontology is used by a logic-based reasoning mechanism for tool recommendation based on the current context of group members. We believe that this ontology could help to understand the role of context in collaboration and thus make the development of context-aware groupware systems easier.

Towards an ontology for context representation in groupware

In times where users need to process an ever increasing amount of information to perform more complex tasks in less time, the introduction of context in computer systems is becoming a necessity. However, building a context-sensitive system entails more work in comparison to traditional systems development: in the former, one must care for context-related tasks, such as the acquisition, processing, storage, manipulation and presentation of contextual elements. Context management proposes the separation of context related tasks from the application's business features. This paper presents a study on context management and discusses our proposal for a context manager, called CEManTIKA (Contextual Elements Management Through Incremental Knowledge Acquisition). A scenario is presented to illustrate its applicability.

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Ana Carolina Salgado

Papers

Designing context-sensitive systems: An integrated approach

Conceptual modeling of XML schemas

Key issues in the design of an asynchronous system to support meeting preparation

Towards an ontology for context representation in groupware

Investigating the specifics of contextual elements management: the CEManTIKA approach