Formalizing nonmonotonic reasoning systems
Artificial Intelligence
A logic for object-oriented logic programming
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Belief revision with unreliable observations
AAAI '98/IAAI '98 Proceedings of the fifteenth national/tenth conference on Artificial intelligence/Innovative applications of artificial intelligence
Characterization of hierarchies and some operators in OLAP environment
Proceedings of the 2nd ACM international workshop on Data warehousing and OLAP
Proceedings of the 2nd ACM international workshop on Data warehousing and OLAP
ACM Computing Surveys (CSUR)
Representation results for defeasible logic
ACM Transactions on Computational Logic (TOCL)
Understanding facts in a multidimensional object-oriented model
Proceedings of the 4th ACM international workshop on Data warehousing and OLAP
The Data Warehouse Lifecycle Toolkit: Expert Methods for Designing, Developing and Deploying Data Warehouses with CD Rom
Modelling Large Scale OLAP Scenarios
EDBT '98 Proceedings of the 6th International Conference on Extending Database Technology: Advances in Database Technology
A Logical Approach to Multidimensional Databases
EDBT '98 Proceedings of the 6th International Conference on Extending Database Technology: Advances in Database Technology
Hypothetical Queries in an OLAP Environment
VLDB '00 Proceedings of the 26th International Conference on Very Large Data Bases
Summarizability in OLAP and Statistical Data Bases
SSDBM '97 Proceedings of the Ninth International Conference on Scientific and Statistical Database Management
CSL '94 Selected Papers from the 8th International Workshop on Computer Science Logic
Querying Multidimensional Databases
DBLP-6 Proceedings of the 6th International Workshop on Database Programming Languages
Maintaining Data Cubes under Dimension Updates
ICDE '99 Proceedings of the 15th International Conference on Data Engineering
The Data Warehouse Lifecycle Toolkit
The Data Warehouse Lifecycle Toolkit
Aggregate queries in peer-to-peer OLAP
Proceedings of the 7th ACM international workshop on Data warehousing and OLAP
On new roll-up possibilities for data stream warehouse
ACST'07 Proceedings of the third conference on IASTED International Conference: Advances in Computer Science and Technology
P2P OLAP: Data model, implementation and case study
Information Systems
Combining objects with rules to represent aggregation knowledge in data warehouse and OLAP systems
Data & Knowledge Engineering
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Enhancing multidimensional database models with aggregation hierarchies allows viewing data at different levels of aggregation. Usually, hierarchy instances are represented by means of so-called rollup functions. Rollups between adjacent levels in the hierarchy are given extensionally, while rollups between connected non-adjacent levels are obtained by means of function composition. In many real-life cases, this model cannot capture accurately the meaning of common situations, particularly when exceptions arise. Exceptions may appear due to corporate policies, unreliable data, or uncertainty, and their presence may turn the notion of rollup composition unsuitable for representing real relationships in the aggregation hierarchies. In this paper we present a language allowing augmenting traditional extensional rollup functions with intensional knowledge. We denoted this language IRAH (Intensional Redefinition of Aggregation Hierarchies). Programs in IRAH consist in redefinition rules, which can be regarded as patterns for: (a) overriding natural composition between rollup functions on adjacent levels in the concept hierarchy; (b) canceling the effect of rollup functions for specific values. Our proposal is presented as a stratified default theory. We show that a unique model for the underlying theory always exists, and can be computed in a bottom-up fashion. Finally, we present an algorithm that computes the revised dimension in polynomial time, although under more realistic assumptions, complexity becomes linear on the number of paths in the hierarchy of the dimension instance.