Applying update streams in a soft real-time database system
SIGMOD '95 Proceedings of the 1995 ACM SIGMOD international conference on Management of data
Quality of service based routing: a performance perspective
Proceedings of the ACM SIGCOMM '98 conference on Applications, technologies, architectures, and protocols for computer communication
Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment
Journal of the ACM (JACM)
NiagaraCQ: a scalable continuous query system for Internet databases
SIGMOD '00 Proceedings of the 2000 ACM SIGMOD international conference on Management of data
Adaptive precision setting for cached approximate values
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
Integrating temporal, real-time, an active databases
ACM SIGMOD Record
Divergence caching in client-server architectures
PDIS '94 Proceedings of the third international conference on on Parallel and distributed information systems
A survey of web caching schemes for the Internet
ACM SIGCOMM Computer Communication Review
Models and issues in data stream systems
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Best-effort cache synchronization with source cooperation
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Temporal and Real-Time Databases: A Survey
IEEE Transactions on Knowledge and Data Engineering
Continual Queries for Internet Scale Event-Driven Information Delivery
IEEE Transactions on Knowledge and Data Engineering
Offering a Precision-Performance Tradeoff for Aggregation Queries over Replicated Data
VLDB '00 Proceedings of the 26th International Conference on Very Large Data Bases
Update Propagation Strategies for Improving the Quality of Data on the Web
Proceedings of the 27th International Conference on Very Large Data Bases
A QoS-Sensitive Approach for Timeliness and Freshness Guarantees in Real-Time Databases
ECRTS '02 Proceedings of the 14th Euromicro Conference on Real-Time Systems
Robust aperiodic scheduling under dynamic priority systems
RTSS '95 Proceedings of the 16th IEEE Real-Time Systems Symposium
A Scalable Solution to the Multi-Resource QoS Problem
RTSS '99 Proceedings of the 20th IEEE Real-Time Systems Symposium
Fjording the Stream: An Architecture for Queries Over Streaming Sensor Data
ICDE '02 Proceedings of the 18th International Conference on Data Engineering
QUASAR: quality aware sensing architecture
ACM SIGMOD Record
Efficiently serving dynamic data at highly accessed web sites
IEEE/ACM Transactions on Networking (TON)
Cache Clouds: Cooperative Caching of Dynamic Documents in Edge Networks
ICDCS '05 Proceedings of the 25th IEEE International Conference on Distributed Computing Systems
Improving web server performance by caching dynamic data
USITS'97 Proceedings of the USENIX Symposium on Internet Technologies and Systems on USENIX Symposium on Internet Technologies and Systems
Monitoring streams: a new class of data management applications
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
Maintaining coherency of dynamic data in cooperating repositories
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
Context-aware systems: A literature review and classification
Expert Systems with Applications: An International Journal
Modeling and assessing quality of information in multisensor multimedia monitoring systems
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)
Middleware support for internetware: a service perspective
Proceedings of the Second Asia-Pacific Symposium on Internetware
Context-sensitive trust computing in distributed environments
Knowledge-Based Systems
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In the future, we are likely to see a tremendous need for context-aware applications which adapt to available context information such as physical surroundings, network, or system conditions. We aim to provide a fundamental support for these applications—a real-time context information collection service. This service delivers the right context information to the right user at the right time. The complexity of providing the real-time context information service arises from 1) the dynamically changing status of information sources, 2) the diverse user requirements in terms of data accuracy and service latency, and 3) constantly changing system conditions. In this paper, we take into consideration these dynamics and focus on addressing the trade-offs between timeliness, accuracy, and cost for information collection in distributed real-time environments. We propose a middleware-based approach to enable a judicious composition of services for accuracy-aware scheduling and cost-aware database maintenance. Specifically, we characterize the problem in terms of Quality-of-Service Satisfaction (QoSSat), Quality-of-Data Satisfaction (QoDSat), and Cost. We propose a middleware framework for the real-time information collection process, where the information mediator coordinates and facilitates communication between information sources and consumers. We design a family of algorithms for real-time request scheduling, request servicing, and directory service maintenance to be implemented at the mediator to support QoSSat and QoDSat. Our studies indicate that the composition of our proposed scheduling algorithm and directory service maintenance policy can improve the overall efficiency of the system. We also observe that the proposed policies perform very well as the system scales in the number of information sources and consumer requests.