| 1. |
- Andler, Sten F, et al.
(författare)
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DeeDS : A Distributed Active Real-Time Database System
- 1995
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Rapport (övrigt vetenskapligt)abstract
- DeeDS combines active database functionality with critical timing constraints and integrated system monitoring. Since the reactive database mechanisms, or rule management system, must meet critical deadlines, we must employ methods that make triggering of rules and execution of actions predictable. We will focus on the scheduling issues associated with dynamic scheduling of workloads where the triggered transactions have hard, firm or soft deadlines, and how transient overloads may be resolved by substituting transactions by computationally cheaper ones. The rationale for a loosely coupled general purpose event monitoring facility, that works in tight connection with the scheduler, is presented. For performance and predictability, the scheduler and event monitor are executing on a separate CPU from the rest of the system. Real-time database accesses in DeeDS are made predictable and efficient by employing methods such as main memory resident data, full replication, eventual consistency, and prevention of global deadlocks.
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| 2. |
- Berndtsson, Mikael, et al.
(författare)
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Coordination Among Agents : Using Reactive Rules
- 1996
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Rapport (övrigt vetenskapligt)abstract
- Coordination and collaboration are naturally used by groups for carrying out activities and solving problems that require cooperation. However, getting a set of computer agents to do that same has been a problem -- primarily addressed by the AI community and recently by the database community as workflow and process management problems (e.g. in business processes, electronic commerce, logistics).Not surprisingly, the problem has been addressed at different levels of abstraction by the two communities. Coordination protocols (both static and dynamic) as well as task and result sharing have been investigated by the AI community; system level support as well as specification and execution of relaxed notions of transaction (sometimes termed an activity) have been addressed by the database community. It is evident that combining the two will provide an effective unified solution for a class of problems that require cooperation. This paper classifies problems addressed in the AI and database literature according to degree of coordination and collaboration. It reports on work done by the authors in utilising the reactive paradigm to synthesize, from the yechniques in these areas, a common framework for the support of multi-agent problem solving, workflow, and process management. In addition to resolving the terminology used by different groups, task sharing is used to demonstrate the approach described. It is accomplished by creating either static or dynamic plans that are coordinated by ECA rules -- both pre-defined and dynamically created. The paper details the applicability of ECA rules in this domain, their adequacy, and a prototype implementation.
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| 3. |
- Berndtsson, Mikael, et al.
(författare)
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Extending Active Capability Mechanisms for Context Based Subscriptions
- 1998
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Rapport (övrigt vetenskapligt)abstract
- Interest has increased recently in synthesizing solutions to CIS problems by using results from the database and distributed AI communities. Such synthesis is not without its difficulties; results do not always transfer seamlessly to a new, complex domain. In this paper we highlight the difficulties encountered in our attempts to use event detection and subscription mechanisms (proposed in current active databases) for the problem of efficient result sharing in CIS. A solution to such problems is described, in the form of a refined, context based subscription mechanism.
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| 4. |
- Berndtsson, Mikael, et al.
(författare)
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Issues in Active Real-Time Databases
- 1995
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Rapport (övrigt vetenskapligt)abstract
- Active databases and real-time databases have gained increased interest in recent. Both active and real-time databases are considered as important technologies for supporting non-traditional applications such as computer integrated manufacturing (CIM), process control and air-traffic control. These applications are often event driven and need to react to events in a timely and efficient manner. In this paper we address the problem of merging active databases and real-time databases. Active real-time database is a fairly new area, in which very little research has been carried out so far. However, the use of active real-time database applications has a great potential. In this paper we address several issues and open questions such as semantics, assignment of time constraints and rule selection, which need to be considered when designing active real-time databases.
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| 5. |
- Berndtsson, Mikael, et al.
(författare)
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Logical Events and ECA Rules
- 1995
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Rapport (övrigt vetenskapligt)abstract
- This paper presents an approach to support event-condition-action rules and logical events in an object-oriented environment. Previous approaches in active object-oriented databases support either traditional event-condition-action rules or logical events. We see the need to integrate these two concepts in order to efficiently support specialization of events.
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| 6. |
- Berndtsson, Mikael, et al.
(författare)
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Systematic Treatment of Events and Rules
- 1995
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Rapport (övrigt vetenskapligt)abstract
- Current prototype Active Object-Oriented database systems introduce powerful event and rule specification languages. We contend that this is not in general done in a uniform and integral manner. We present a modified design for an ACtive Object-Oriented DBMS (ACOOD) currently under development at the University of Skovde. The design emphasises the key concepts being investigated, namely Events and Rules as 1st Class (ER1C). It is important because it addresses the key issue of inheritance, something not prominent in current prototype systems with a fully developed event specification system. Key features in the design are that it has a unifying concept of primitive event and of behaviour, and achieves uniformity and power with respect to inheritance. It further relates this to event specification languages for composite events, guaranteeing orthogonality of features. The paper emphasises modeling concepts, and the design is therefore of relevance to all active, object-oriented database systems. It seeks to explore the wider implications and underpinnings of current active O-O suggestions rather than enriching event and/or rule specification languages.
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| 7. |
- Birgersson, Ragnar, et al.
(författare)
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Bounds on Test Effort for Event-Triggered Real-Time Systems
- 1999
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Rapport (övrigt vetenskapligt)abstract
- The test effort required for full test coverage is much higher in an event-triggered than in a time-triggered real-timesystem. This makes it difficult to attain confidence in the correctness of event-triggered real-time applications by testing,which is a necessary complement to other verification methods. We present a more general upper bound on the test effort of constrained event-triggered real-time systems, assuming multiple resources (a refinement of previous results). The emphasis is on system level testing of application timeliness, assuming that sufficient confidence in its functional correctness has been attained. Covered fault types include incorrect assumptions about temporal attributes of application and execution environment, and synchronization faults. An analysis of the effects that our constraints have on predictability and efficiency shows that the use of designated preemption points is required. A key factor in this approach is the ability to reduce the number of required test cases while maintaining full test coverage.
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| 8. |
- Biro, Zoltan, et al.
(författare)
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Evolution of visually-guided approach behaviour in recurrent artificial neural network robot controllers.
- 1998
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Rapport (övrigt vetenskapligt)abstract
- Analysis of internal structures of embodied and situated agents may provide insights into the mechanisms underlying adaptive behaviour. This paper is concerned with the evolution and analysis of visually-guided approach behaviour in a simulated robotic agent controlled by a recurrent artificial neural network, whose connection weights have been evolved using evolutionary algorithms. Analysis of the evolved behaviours and their network-internal mechanisms reveals a behavioural structure and organization resembling a Brooksian subsumption architecture. The task decomposition, as well as the resulting individual behaviours and their integration, however, are realized as network-internal state space dynamics, evolved in the course of agent-environment interaction, i.e. with a minimum of designer intervention.
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| 9. |
- Bodén, Mikael
(författare)
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A Connectionist Variation on Inheritance
- 1996
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Rapport (övrigt vetenskapligt)abstract
- A connectionist architecture is outlined which makes use of RAAM to generate representations for objects in inheritance networks and extended learning to make such representations context-sensitive. The architecture embodies inheritance quite differently by relying on associative similarities and regions in representational space. The model avoids many of the problems identified for traditional inheritance.
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| 10. |
- Bodén, Mikael, et al.
(författare)
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Features of distributed representations for tree-structures: A study of RAAM
- 1995
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Rapport (övrigt vetenskapligt)abstract
- This paper presents an in-depth analysis of properties of patterns, generated by the Recursive Auto-Associative Memory, based on the idea that representational features can be detected by a classification network. The intension of this analysis is to examine the actual reasons for the success of connectionist processes acting on super-positional activity vectors generated in the fashion described. We show that the structure supplied during training is maintained and is extractable from the generated pattern. Further, we show that the influence of the actual constituents in the structures supplied during training is not necessarily available, in the generated patterns, for holistic processing. The outlook for holistic processing is therefore limited unless new forms can be found which take into account, what Sharkey and Jackson call, `whole net' representations.
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