In this poster, we present the P2P XML data localization layer of XLive, an XQuery mediation system developed at University of Versailles [2]. A major challenge in the evaluation of XQuery over a P2P network in the context of multiple XML sources is to abstract from structural heterogeneity. Most existing approaches have mainly exploited varied types of 1:1 semantic mappings between peer schemas and/or ontologies. Complex query algorithms are required to exploit these semantic links between peers. In contrast, our approach focuses on a simple semantic layer. It is built on a Chord [4] DHT for indexing semantic descriptions of mediated data sources. A mapping process transforms an XML view of a mediator (each peer is equipped with a mediator) to a semantic form that is published into the P2P network and stored in the DHT. For a given user query, a search in the DHT retrieves all relevant data sources able to contribute to the result elaboration. Then, every peer that contains relevant data is directly queried to collect data for elaborating the final answer.

The current abundance and complexity of P2P architectures makes it extremely difficult to assess their performance. P2PTester is the first tool devised to interface with, and measure the performance of, existing P2P data management platforms. We isolate basic components present in current P2P platforms, and insert "hooks" for P2PTester to capture, analyze and trace the interactions taking place in the underlying distributed system.