Proceedings of the 2nd ACM international workshop on Data warehousing and OLAP
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Low Complexity Aggregation in GraphLog and Datalog
ICDT '90 Proceedings of the Third International Conference on Database Theory
Revising aggregation hierarchies in OLAP: a rule-based approach
Data & Knowledge Engineering - Special issue: Advances in OLAP
Maintaining Data Cubes under Dimension Updates
ICDE '99 Proceedings of the 15th International Conference on Data Engineering
Mapping data in peer-to-peer systems: semantics and algorithmic issues
Proceedings of the 2003 ACM SIGMOD international conference on Management of data
Efficient query reformulation in peer data management systems
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Aggregate queries in peer-to-peer OLAP
Proceedings of the 7th ACM international workshop on Data warehousing and OLAP
Logical foundations of peer-to-peer data integration
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Approximating Aggregation Queries in Peer-to-Peer Networks
ICDE '06 Proceedings of the 22nd International Conference on Data Engineering
Efficient Approximate Query Processing in Peer-to-Peer Networks
IEEE Transactions on Knowledge and Data Engineering
Mapping maintenance in XML p2p databases
DBPL'05 Proceedings of the 10th international conference on Database Programming Languages
Inconsistency tolerance in P2P data integration: an epistemic logic approach
DBPL'05 Proceedings of the 10th international conference on Database Programming Languages
Query answering in peer-to-peer data exchange systems
EDBT'04 Proceedings of the 2004 international conference on Current Trends in Database Technology
Online querying of d-dimensional hierarchies
Journal of Parallel and Distributed Computing
Brown Dwarf: A fully-distributed, fault-tolerant data warehousing system
Journal of Parallel and Distributed Computing
OLAP query reformulation in peer-to-peer data warehousing
Information Systems
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It is a common situation nowadays that business groups own different companies that operate in an autonomous way. Nevertheless, these companies must be requested to provide the headquarters with summarized information for decision-making. An architecture for cooperative interchange of decision-making information seems to be a natural solution for this problem. We propose the use of a peer-to-peer (P2P) architecture for addressing the problem of processing OLAP data in a distributed environment, in a way that all companies involved can maintain full autonomy over the use of its own data resources. In a scenario like this, data exchange between peers occurs when one of them, in the role of a local peer, receives a query and, for answering it, requests data available in other nodes, denoted acquaintances. No global schema is assumed to exist for any data under this computing paradigm. Henceforth, data provided by an acquaintance of a local peer must be adapted, in a manner that answers to queries posed by local peer users conform the view those users have of their data. Because multidimensional data normally consist of a collection of views of aggregated data, a careful translation process is needed in this case, in order to transform any summary concept that appears in a peer acquaintance into a summary concept meaningful to the requesting peer. We first present a model for multidimensional data distributed in a P2P network, and a query rewriting technique, that allows a local peer to propagate OLAP queries among its acquaintances, obtaining a meaningful and correct answer. Mappings are performed using a novel technique called revise and map, based on belief revision concepts. Revising a dimension instance allows to produce consistent aggregations when an OLAP query is answered at more than one node. We then describe an implementation of a P2P system for answering OLAP queries over a network of data warehouses. We apply our proposal to a real-world case study of an insurance group. Finally, we report the results of an experimental evaluation of our implementation, and discuss the issues that must be accounted for in this setting.