| dc.description.abstract | The development of distributed multimedia applications has increased
in the last few years. Multimedia database systems are introduced in
several types of application systems, for example education systems,
medical care systems and entertainment business. Distributed
multimedia systems include different types of components, for
example the multimedia database, traditional file servers, network
components and end user applications. It is necessary that the
components involved in the system are able to commit to Quality
of Service (QoS) contracts defining the quality level that the
components must deliver.
In the OMODIS project a framework for QoS management has been
developed. The framework separates the QoS management functions from
the application components. The framework defines a QoS management
hierarchy that consists of two types of QoS managers. Strategic
managers control QoS on high levels in the hierarchy, while tactical
managers control QoS on the lowest level in the hierarchy. A tactical
manager represent one specific application component, and perform QoS
management functions on behalf of this component. A tactical manager
consists of three QoS-aware agents that perform QoS negotiation,
adaptation, and resource management, and a QoS-unaware feedback
controller.
in this master thesis, we present a tactical manager designed for QoS
management in a MM-DBMS. We describe four types of communication that
the tactical manager and the MM-DBMS participate in, and the internal
protocols used for information exchange between the QoS-aware agents
in the tactical manager. We use the specification language Promela to
formally specify the protocols and correctness criteria for them. We
use the protocol simulation and validation tool Spin to simulate the
Promela specification, and to verify that the criteria specified are
not violated.
The QoS negotiation model described by the OMODIS framework is based
on two orthogonal activities: Negotiation of contract terms, and
approval of the negotiated contract terms. QoS negotiation protocols
are executed directly between tactical managers, and the QoS contract
terms that the managers agree to, are sent to the strategic managers
for approval. The QoS negotiation protocol is not defined by the
negotiation model, but the OMODIS framework defines the protocols used
for contract approval. The negotiation process is supported by a local
adaptation process where the MM-DBMS is configured and resources are
reserved.
We describe the QoS negotiation model in detail, and we show how the
model can be used by a tactical manager representing a MM-DBMS. We
present criteria for characteristics that such a negotiation model
should have, and evaluate the model according to these criteria. We
find that the negotiation model is a powerful, flexible model. The
model enables a combination of general mechanisms defined by the QoS
framework, and mechanisms that are specially designed for the managed
component. | nor |