Improving User Interaction on Ontology-based Peer Data Management Systems

The issue of user interaction for query formulation and execution has been investigated for distributed and dynamic environments, such as Peer Data Management System (PDMS). Many of these PDMS are semantic based and composed by data peers which export schemas that are represented by ontologies. In the literature we can find some proposed PDMS interfaces, but none of them addresses, in a general way, the needs of a PDMS for user interaction. In this work we propose a visual user query interface for ontology-based PDMS. It provides a simple and straightforward interaction with this type of system. It aims not only providing a natural visual query interface but also supporting a precise and direct manipulation of the data schemas for query generation.

Ontology-Based Clustering in a Peer Data Management System

Peer Data Management Systems (PDMSs) are advanced P2P applications in which each peer represents an autonomous data source making available an exported schema to be shared with other peers. Query answering in PDMSs can be improved if peers are efficiently disposed in the overlay network according to the similarity of their content. The set of peers can be partitioned into clusters, so as the semantic similarity among the peers participating into the same cluster is maximal. The creation and maintenance of clusters is a challenging problem in the current stage of development of PDMSs. This work proposes an incremental peer clustering process. The authors present a PDMS architecture designed to facilitate the connection of new peers according to their exported schema described by an ontology. The authors propose a clustering process and the underlying algorithm. The authors present and discuss some experimental results on peer clustering using the approach.

SCHEMA MEDIATION IN PEER DATA MANAGEMENT SYSTEMS

Peer Data Management Systems (PDMSs) allow the efficient sharing of data between peers with overlapping sources of information. These sources share data through mappings between peers. In current systems, queries are asked over each peer's local schema and then translated using the mappings between peers. While this allows the data to be accessed uniformly, users lack access to information that is not in their own schemas. In this paper, we propose a light-weight, automatic method to create a mediated schema in a PDMS. Our work benefits PDMSs by allowing access to more data and without unduly stressing the peer's resources or requiring additional resources such as ontologies. We present our system — MePSys, which creates a mediated schema in PDMSs automatically using the existing mappings provided to translate queries. We further discuss how to update the mediated schema in a stable state, i.e. after the system setup period.