Title: Decentralized Service Selection and Composition
Other Titles: Gedecentraliseerde service selectie en compositie
Authors: Cruz Torres, M├írio Henrique
Issue Date: 27-Apr-2015
Abstract: Services computing facilitates the creation of large scale applications.
Servicesnbsp;relatively small and manageable software units with clearly
defined interfaces. Applications then consist of orchestrated invocations of
services, the so-called composite services. The services on which a
composite service relies - called component services - have various quality
of service (QoS) characteristics, such as performance, reliability,
availability, accuracy. Such quality parameters can be used by a composite
service to select component services when called for. Service selection and
composition is particularly challenging when the system is large-scale -
consisting of thousands of nodes, components and composite services - and
dynamic - where QoS varies.

Particularly challenging is the situation where potentially large failures
can occur. This thesis ambition is to create a highly resilient system for
dynamic service compositions. While traditionally, a resilient system is
able to deal with failures, our aim is to conceive a system that considers
failures as ‘business as usual’, to which it gracefully molds itself.

The large or potentially huge scale of such systems (involving tens of
thousands of nodes and services) makes a central selection and composition
nbsp;infeasible. In our research, we investigate a decentralized
nbsp;and self- organizing approach to dynamic service composition.
In particular, we study delegateMAS, a coordination mechanism originally
targeted for large-scale coordination and control applications, such as
traffic and logistics management, where entities need to coordinate over
nbsp;Such coordination and control systems are intrinsically dynamic
due to changes in operational (uncertainty of service time, orders, travel
demand) or exceptional conditions (vehicle failures, infrastructure

nbsp;this thesis we, first, define a decentralized solution for dynamic
service composition using delegate MAS. We define TaskAgents that are
responsible for enacting composite service instances, and ResourceAgents
that manage the usage of component services. Two delegate MASs are defined,
nbsp;exploring compositions and for propagating information about intended
compositions. Second, we thoroughly investigate the scaling of the system.
nbsp;ran experiments that were large and huge in scale (up to tens of
thousands of nodes and services). Third, we assess the behavior of the
system under failing conditions, including drastic failure scenarios. These
experiments show that the approach is effective, efficient, scales linearly,
and cannbsp;even with severe failures.

We validate our approach by applying it to different domains and by
performing a thorough evaluation of it.

We conclude this thesis showing that it is possible to create service
compositions which can cope with failures, without relying on centralized
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Informatics Section

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