| 1. |
- Nyström, Dag, et al.
(author)
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Database pointers : A predictable way of manipulating hot data in hard real-time systems
- 2004
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In: Real-Time and Embedded Computing Systems and Applications. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540219743 - 9783540246862 - 3540219749 ; , s. 454-465
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Book chapter (peer-reviewed)abstract
- Traditionally, control systems use ad hoc techniques such as shared internal data structures, to store control data. However, due to the increasing data volume in control systems, these internal data structures become increasingly difficult to maintain. A real-time database management system can provide an efficient and uniform way to structure and access data. However the drawback with database management systems is the overhead added when accessing data. In this paper we introduce a new concept called database pointers, which provides fast and deterministic accesses to data in hard real-time database management systems compared to traditional database management systems. The concept is especially beneficial for hard real-time control systems where many control tasks each use few data elements at high frequencies. Database pointers can co-reside with a relational data model, and any updates made from the database pointer interface are immediately visible from the relational view. We show the efficiency with our approach by comparing it to tuple identifiers and relational processing.
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| 2. |
- Tesanovic, Aleksandra, et al.
(author)
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Towards aspectual component-based development of real-time systems
- 2003
-
In: Real-Time and Embedded Computing Systems and Applications. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540219743 - 9783540246862 - 3540219749 ; , s. 558-577
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Book chapter (peer-reviewed)abstract
- Increasing complexity of real-time systems, and demands for enabling their configurability and tailorability are strong motivations for applying new software engineering principles, such as aspect-oriented and component-based development. In this paper we introduce a novel concept of aspectual component-based real-time system development. The concept is based on a design method that assumes decomposition of real-time systems into components and aspects, and provides a real-time component model that supports the notion of time and temporal constraints, space and resource management constraints, and composability. We anticipate that the successful applications of the proposed concept should have a positive impact on real-time system development in enabling efficient configuration of real-time systems, improved reusability and flexibility of real-time software, and modularization of crosscutting concerns. We provide arguments for this assumption by presenting an application of the proposed concept on the design and development of a configurable embedded real-time database, called COMET. Furthermore, using the COMET system as an example, we introduce a novel way of handling concurrency in a real-time database system, where concurrency is modeled as an aspect crosscutting the system.
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| 3. |
- Amirijoo, Mehdi, et al.
(author)
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Algorithms for managing QoS for real-time data services using imprecise computation
- 2004
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In: Real-Time and Embedded Computing Systems and Applications 9th International Conference, RTCSA 2003, Tainan City, Taiwan, February 18-20, 2003. Revised Papers. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 3540219749 - 9783540219743 ; , s. 136-157
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Book chapter (peer-reviewed)abstract
- Lately the demand for real-time data services has increased in applications where it is desirable to process user requests within their deadlines using fresh data. The real-time data services are usually provided by a real-time database (RTDB). Here, since the workload of the RTDBs cannot be precisely predicted, RTDBs can become overloaded. As a result, deadline misses and freshness violations may occur. To address this problem we propose a QoS-sensitive approach to guarantee a set of requirements on the behavior of RTDBs. Our approach is based on imprecise computation, applied on both data and transactions. We propose two algorithms to dynamically balance the workload and the quality of the data and transactions. Performance evaluations show that our algorithms give a robust and controlled behavior of RTDBs, in terms of transaction and data quality, even for transient overloads and with inaccurate run-time estimates of the transactions.
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