Managing Semantic Loss during Query Reformulation in Peer Data Management Systems

In this paper we deal with the notion of semantic loss in Peer Data Management Systems (PDMS) queries. We define such a notion and we give a mechanism that discovers semantic loss in a PDMS network. Next, we propose an algorithm that addresses the problem of restoring such a loss. Further evaluation of our proposed algorithm is an ongoing workComment: SWOD '07 Proceedings of the 2007 IEEE International Workshop on Databases for Next Generation Researcher

A New Framework for Join Product Skew

Different types of data skew can result in load imbalance in the context of parallel joins under the shared nothing architecture. We study one important type of skew, join product skew (JPS). A static approach based on frequency classes is proposed which takes for granted the data distribution of join attribute values. It comes from the observation that the join selectivity can be expressed as a sum of products of frequencies of the join attribute values. As a consequence, an appropriate assignment of join sub-tasks, that takes into consideration the magnitude of the frequency products can alleviate the join product skew. Motivated by the aforementioned remark, we propose an algorithm, called Handling Join Product Skew (HJPS), to handle join product skew

Strategic delegation in a sequential model with multiple stages

We analyze strategic delegation in a Stackelberg model with an arbitrary number, n, of firms. We show that the n-1 last movers delegate their production decisions to managers whereas the first mover does not. Equilibrium incentive rates are increasing in the order with which managers select quantities. Letting u_i^* denote the equilibrium payoff of the firm whose manager moves in the i-th place, we show that u_n^*>u_{n-1}^*>...>u_2^*>u_1^*. We also compare the delegation outcome of our game with that of a Cournot oligopoly and show that the late (early) moving firms choose higher (lower) incentive rates than the Cournot firms.Comment: To appear in International Game Theory Review (IGTR), Vol. 13, No. 3 (2011) 1-1