Marie-Jo Bellosta

A multi-criteria model for electronic auctions

In this paper we present a multi-criteria model for electronic auctions, which is based on reference points. According to the model, the buyer must specify an aspiration point that expresses his desired values on the attributes of the item to be purchased and a reservation point that represents the minimal values required. Negotiation takes place between software agents that negotiate on behalf of their human owners. The multi-criteria model allows the buyer agent to control the negotiation process on each attribute of the deal. We illustrate the use of this model by providing an auction mechanism based on an English reverse auction protocol.

A unified framework for multiple criteria auction mechanisms

Multi-attribute auctions allow negotiations over multiple attributes besides price. Multiple criteria English reverse auction mechanisms differ regarding the aggregation model used to represent the buyers preferences and the feedback information provided to bidders during the auction. In this paper, we present a unified framework, called MERA in order to integrate existing mechanisms and guide the design of new ones. Framework MERA both provides an automated buyer agent that manages auctions and a formal model that describes an auction mechanism. This model includes a class of preference relations used to express the buyers preference relation, a class of request relations used to formulate the feedback, and a class of constraints used to express the initial requirements on the purchased item. We study efficiency for multiple criteria English reverse auction processes, and we show that any process derived from framework MERA is efficient.

Preference-based English reverse auctions

This paper studies English reverse auctions within a unified framework for preference-based English reverse auctions. In this context, and particularly for electronic auctions, representing and handling the buyer@?s preferences, so as to enable him/her to obtain the best possible outcome, is a major issue. Existing auction mechanisms, which are based on single or multi-attribute utility functions, are only able to represent transitive and complete preferences. It is well known, however, in the preference modeling literature that more general preference structures, allowing intransitivity and incomparability, are more appropriate to capture preferences. On the other hand, we must also consider properties on the evolution and, above all, on the outcome of any auction executed by an auction mechanism. These properties, as well as properties of non-dominance and fair competition defined for multiple criteria auctions, impose restrictions on the preference relation. This leaves room for interesting preference models to be implemented within English reverse auction mechanisms.

Multiversion views: constructing views in a multiversion database

Abstract Commercial DBMS offer mechanisms for views and for versions. Research and development efforts in these directions are, however, characterized by concentration on either the one or the other mechanism, very seldom trying to take advantage of their complementary properties. This paper presents the multiversion view mechanism , which allows these orthogonal concepts to be managed together, taking advantage of their combined characteristics. Unlike previous efforts to combine views and versions, multiversion views create views over versions of data, thereby offering users coherent logical units of the versioned world. They allow a wide range of (virtual) data reorganization possibilities, which encompass, among others, operations found in temporal databases and OLAP. Multiversion views are illustrated and motivated by needs from a real life large case study of complex configuration management, described at the end of the paper.

Type-safe relaxing of schema consistency rules for flexible modelling in OODBMS

Abstract. Object-oriented databases enforce behavioral schema consistency rules to guarantee type safety, i.e., that no run-time type error can occur. When the schema must evolve, some schema updates may violate these rules. In order to maintain behavioral schema consistency, traditional solutions require significant changes to the types, the type hierarchy and the code of existing methods. Such operations are very expensive in a database context. To ease schema evolution, we propose to support exceptions to the behavioral consistency rules without sacrificing type safety. The basic idea is to detect unsafe statements in a method code at compile-time and check them at run-time. The run-time check is performed by a specific clause that is automatically inserted around unsafe statements. This check clause warns the programmer of the safety problem and lets him provide exception-handling code. Schema updates can therefore be performed with only minor changes to the code of methods.

A Model-Independent Object Schema Manager*

In this paper, we propose an object management interface system (OMNIS) intended for use by OO tools, e.g., compilers, interpreters or CAD/CAM programs, which require support for managing persistent objects. Through extensibility, it achieves a high degree of independence with respect to both the object models of the client OO tools and the underlying object managers. To this end, we use a reflexive object model allowing the dynamic creation of meta-description levels to capture new object models. Implementing this model implies being able to create objects whose type, i.e. structure and behavior, is dynamically defined, a kind of genericity normally impossible in a typed and compiled language like C++. The idea is then to build our own type layer on top of C++ type system to describe the structure and behavior of objects. To build this layer, we use polymorphic structures and abstract function invocation. Finally, we define the notion of a manager to capture each aspect of an object model such as instantiation, inheritance or aggregation.

Schema Extensions in OODB

In this paper, we extend the schema evolution operations of a schema manager called Omnis, considering semantical aspects. The proposed object view integration method (Ovi), is intended to help the DBA and Omnis users in integrating new classes in an oodb schema, with automatic enforcement of database consistency and non redundancy. Ovi uses the generic data model of Omnis as conceptual model to gain independence from the persistent object-oriented programming language. It also exploits an OO methodology to provide extensibility. It is implemented in C++.