Björn Schnizler

Bibster-a semantics-based bibliographic Peer-to-Peer system

This paper describes Bibster, a Peer-to-Peer system for exchanging bibliographic metadata among researchers. We show how Bibster exploits ontologies in data-representation, query formulation, query routing, and query result presentation. The Bibster system is freely available and is used by researchers across multiple organizations.

Trading grid services - a multi-attribute combinatorial approach

Abstract The Grid is a promising technology for providing access to distributed high-end computational capabilities. Thus, computational tasks can be performed spontaneously by other resources in the Grid that are not under the user’s control. However, one of the key problems in the Grid is deciding which jobs are to be allocated to which resources at what time. In this context, the use of market mechanisms for scheduling and allocating Grid resources is a promising approach toward solving these problems. This paper proposes an auction mechanism for allocating and scheduling computer resources such as processors or storage space which have multiple quality attributes. The mechanism is evaluated according to its economic and computational performance as well as its practical applicability by means of a simulation.

Catallaxy-based Grid markets

Grid computing has recently become an important paradigm for managing computationally demanding applications, composed of a collection of services. The dynamic discovery of services, and the selection of a particular service instance providing the best value out of the discovered alternatives, poses a complex multi-attribute n:m allocation decision problem, which is often solved using a centralized resource broker. To manage complexity, this article proposes a two-layer architecture for service discovery in such Application Layer Networks (ALN). The first layer consists of a service market in which complex services are translated to a set of basic services, which are distinguished by price and availability. The second layer provides an allocation of services to appropriate resources in order to enact the specified services. This framework comprises the foundations for a later comparison of centralized and decentralized market mechanisms for allocation of services and resources in ALNs and Grids.

Bibster: a semantics-based bibliographic peer-to-peer system

This paper describes the design and implementation of Bibster, a Peer-to-Peer system for exchanging bibliographic data among researchers. Bibster exploits ontologies in data storage, query formulation, query routing and answer presentation: When bibliographic entries are made available for use in Bibster, they are structured and classified according to two different ontologies. This ontological structure is then exploited to help users formulate their queries. Subsequently, the ontologies are used to improve query routing across the Peer-to-Peer network. Finally, the ontologies are used to postprocess the returned answers in order to do duplicate detection. The paper describes each of these ontology-based aspects of Bibster. Bibster is a fully implemented open source solution built on top of the JXTA platform.

Personalized Information Access in a Bibliographic Peer-to-Peer System

The Bibster system is an application of the use of semantics in Peer-to-Peer systems, which is aimed at researchers that share bibliographic metadata. In this paper we describe the design and implementation of recommender functionality in the Bibster system which allows personalized access to the bibliographic metadata available in the Peer-to-Peer network. These functions are based on a semantic user profile which is created from content and usage information as well as a similarity function. Furthermore, these functions make use of the semantic topology of the Peer-to-Peer system.

Trading services in ontology-driven markets

In order to realize the vision of a full-fletched service oriented architecture efficient service discovery and allocation is required to coordinate the interplay between service providers and requesters. This paper presents the architecture of an ontology-driven market for trading Semantic Web Services. An auction schema is enriched by a set of components enabling semantics based matching as well as price-based allocations. Moreover, an approach for reducing the complexity of the auction system by means of background knowledge is proposed.

MACE: A Multi-attribute Combinatorial Exchange

The Grid is a promising technology for providing access to distributed computational capabilities such as processors or storage space. One of the key problems in current Grid infrastructures is deciding which jobs are to be allocated to which resources at what time. In this context, the use of market mechanisms for allocating resources is a promising approach toward solving these problems. This paper proposes an auction mechanism for allocating and scheduling computer resources which have multiple quality attributes and time constraints. The mechanism is evaluated according to its economic performance by means of a numerical simulation.

Second-Best Combinatorial Auctions - The Case of the Pricing-Per-Column Mechanism

One of the main contributions of classical mechanism design is the derivation of the Groves mechanisms. The class of Groves mechanisms are the only mechanisms that are strategy-proof and more importantly allocative efficient. The VCG mechanism retains its properties for combinatorial allocation problems. From a computational perspective the VCG has to solve two problems: (1) the winner-determination (2) the determination of the prices. However, both problems are complex (NP-hard), when complementarities are present. The pricing-per-column (PPC) auction is another approach to solve the combinatorial allocation problem. In essence, it applies the Vickrey principle to any possible combination of goods and determines the overall winning bids. PPC is computationally less demanding, however, it can be shown that PPC is not necessarily efficient. Apparently, solving the tension between computational and game-theoretic properties is a challenging task in mechanism design. Engineering auctions suggests to lower requirements upon the auction. In this paper the evaluation of the PPC concerning approximate efficiency is presented - in an analytical and simulative evaluation the PPC is compared to the VCG and it is shown that the efficiency losses incurred by the PPC mechanism are very small

Combinatorial exchanges for coordinating grid services

In this paper, two combinatorial exchange mechanisms MACE and GreedEx are introduced that are suitable for resource allocation in service-oriented environments such as Grids. MACE provides users with a fairly complex bidding language offering flexibility in the bidding process. This flexibility comes at the expense of computational tractability. GreedEx tremendously restricts the bidding language and thereby reduces the problem complexity considerably. As with any practical mechanism design effort, the designed artifact does not implement desirable allocations in dominant strategies. In this short paper we also introduced jCase as tool for evaluating the market outcome when agents are acting strategically on the market for Grids.