Catálogo de publicaciones - libros

Many research areas related to Internet (resource discovery, intelligent browsing and navigation, data search and retrieval...) are developing agents and adaptive systems whose main target is to help the user to manage the large quantity of information available through Internet. A detailed knowledge of users behaviour when navigating or using services provided by Internet is a vital component for many of these agents and systems. There are other areas (data mining, data caching, web design...) where getting a thorough knowledge of Internet dynamics and ergonomics is advisable. They could also profit by a precise description of the user behaviour. Nowadays Internet user behaviour traces are mainly collected at the servers or proxies. Detecting the behaviour at the server-side provides just a partial vision of the user, where only the behaviour inside the server is controlled. Furthermore, many behaviour features which appear at the client-side are impossible to detect by the server. In this paper we introduce , a distributed, cross-platform, lightweight tool that gathers in detail the behaviour of a user navigating the web.

Content providers try to restrict the usage of their products by their customers in order to prevent unlicensed distribution. On the other hand, customers ignore these restrictions and share files for free (Gnutella). Content providers and content users treat one another as enemies with conflicting interests. In this paper we bring customers and providers of content back together to a common economic interest. Content providers support their customers to redistribute their products in that they pay for any re-distributed multimedia product a small percentage on commission. Customers have a choice to pay for a received copy or to use it freely. If they use it for free, they will get no commission on re-distribution. If they pay, they will become licensed re-distributors automatically. This paper describes a friendly peer-to-peer file-sharing model of customers, which brings profit to both, content providers and their customers. We will also specify a protocol for payment and re-distribution. We will describe open interfaces and file formats, which are needed for implementation.

Today, the management of information resources in the Internet is mostly realized by centralized services. Clients can contact the server and access these resources. Nevertheless, the classic client-server architecture suffers from some limitations caused by holding every data in one central place.

Internet communities are groups of individuals sharing a common interest or work scope. The connection between the members of a community creates a logical structure overlying the physical network structure. The community structure can be adapted and modified. This allows the appliance of some efficient and innovative algorithms and techniques. This is realized in the AWeb information management system.

In the contribution, a decentralized library for scientific articles based on the AWeb middelware is presented and the main concepts of the AWeb will be summarized in brief.

The complex structure of the Web requires decentralised, adaptive mechanisms efficiently providing access to local and global capacities. To facilitate the development of such mechanisms, it seems reasonable to build clusters of machines with similar structures and interests. In such a manner, communities of machines can be built. In a community, every machine contributes to the overall success through a division of management work and a respective collaboration. This article presents and analyses experimental results for algorithms optimising service response times in a community. It extends previously published results on the optimisation algorithm; we describe variations of the and present simulation results of these variations.

This paper analyses, using Unified Modelling Language, end-users’ and applications’ common basic requirements towards a QoS enabled network. It provides the basis for a QoS description language, the so called Application Profile (AP) supporting mapping mechanisms between application, end-user and network. Based on this analysis the paper introduces five practically implemented Network Services (NS), designed for large networks with the aim to manage the resources. The underlying mechanisms at network level and QoS capabilities of routers, allowing appropriate handling of underlying Traffic Classes (TC) by adaptation of scheduling and queuing parameters, are presented. Considering the proof of the requirements active and passive measurements with high precision are introduced. Data is collected in a central database, verifying the specifications and allowing adjustments for admission control as well as technical parameters at network level.

Replicated real-time applications such as co-operative document editors have to continuously update a shared state, thus require low network delays. If we use such applications in mobile and weakly connected environments, state information often cannot be broadcasted immediately, and thus it is difficult to maintain consistency. We discuss this problem with the help of , our framework for distributed applications, which we extend to the mobile version . The DreamTeam environment allows the developer to generate replicated applications (e.g., collaborative diagram tools, multi-user text editors, shared web browsers) in the same way as single user applications, without struggling with network details or replication algorithms. For our mobile extension, we suggest an architectural decomposition according to the . This architecture has a number of benefits: it tolerates weakly connected devices and allows a developer to heavily re-use existing stationary applications.

This work presents the result of the empirical study on the effect of VBR smoothing in broadband wireless network. Traffic smoothing of VBR stream has been the subjects of intense research during past several years. While preceding algorithms successfully remove burstiness in the underlying process, these works do not address how the respective smoothing algorithm can effectively improve the QoS in practical environment. We developed MPEG-4 streaming system and instrument the client terminal which is handheld mobile device. We examine the effect of smoothing over the packet loss behavior and empirical QoS under various different system settings. We use the rate variability as optimization criterion in generating the packet transmission schedule. We find that smoothing with small size buffer(10 Kbyte) brings a significant improvement on packet loss ratio and greatly enhances the QoS perceived by the end user. Via adopting smoothing technique in transporting multimedia traffic, we are able to increase the frame rate by 50%.

A set of geologically distributed databases can be connected through the internet and served as a single database to the user. To connect them, we need a global manager that can interface the user and convey user’s requests to the local databases, and an agent for each database that can translate the global manager’s requests to the local database commands. The per-database agent not only processes the user’s database requests, but also performs integrity checking on the requested database operations. Since integrity constraints are expressed as rules and maintained by the global manager too, an efficient way of integrity checking in the local agent is needed. Conventional technique is either introducing another agent in the local database that monitors the behavior of the request-processing agent and handles integrity checking when there is a need, or hard-coding the rules into the local agent. The former suffers a delay in request processing due to the communication overhead between the agent and the global manager, while the latter lacks flexibility on adapting to changing rules and programmability because it is typically very hard for a regular application programmer to understand and code properly the complex integrity rules. This paper proposes a compiler-based solution that does not cause a heavy communication overhead, and is flexible enough to accommodate changing rules, and shifts the burden of rule coding from individual programmers to the compiler. We explain the technique and show its effectiveness using examples from spatial distributed databases.

In this paper we present a formal framework for the definition of architectures. By e-barter we mean the possibility of (electronically) exchanging goods without reducing transactions to money. Actually, in our setting, money can be considered just as another , so that e-barter generalizes seller/buyer architectures. An advantage of e-barter systems, in contrast with most current systems, is that multilateral exchanges can be performed. Customers are first grouped into markets, according mainly to their localities. Next, a higher order construction allows to compose markets, so that a takes a tree-like shape.

In order to methodically build our systems, we consider a process algebraic notation. This allows us to specify all the stages of a system (from customers to markets, markets of markets, etc). We introduce an operational semantics for our language so that exchanges of goods are formally defined. Besides, we use some concepts borrowed from microeconomic theory. Specifically, we consider utility functions (i.e. functions returning the valuation that customers/markets give to goods), exchange of goods, and equilibria.

We will show that the integration of microeconomic theory and process algebras provides two important . Firstly, it allows to avoid ambiguity in the understanding of the behavior of systems. Secondly, it gives a scheme to appropriately structure, in a bottom-up way, e-barter systems.

Peer-to-peer architectures gained much attention through their main application domain file sharing. First, we analyze the music industry and the architectural innovations of online services for sharing music files on the business model of the music industry. In the second main part of the paper, we generalize our observations to the design of media for the creation of economic value and the social and economic impact of peer-to-peer architectures. We analyze here virtual communities and other peer-to-peer architectures.