Student Project Proposal:

Reputation-based Quality of Service Monitoring for Service Oriented Environments


Radu Jurca
Office: INR 240
Tel: +41-21-6936711

Project Type

Diploma/Semester project for one or two students.



Service oriented IT systems offer the flexibility required by present business organizations. The monolithic systems are replaced by loosely coupled components that offer services characterized by certain functional (i.e. interface) as well as non-functional (i.e. quality) parameters. Complex tasks can be easily achieved by (automatically) aggregating several services. The resulting service-oriented architecture can adapt to changing business environments, is easier to maintain and much cheaper to operate.

However, as different services may be provided by self-interested organizations, it becomes essential to ensure that the quality parameters promised by the provider are actually delivered. Take for example a web-service providing stock-quotes (i.e. a service that can be invoked to find the price of a certain stock). When the service provider promises that 99% of the requests are answered within one minute, it must also invest in the infrastructure that technically permits to keep this promise. Quality therefore comes at a cost, and rational providers are not expected to assume this cost, unless they are constrained to do so.

One way to ensure that providers act honestly is to introduce penalties as part of the contract (or Service Level Agreements - SLAs) that regulates the transaction between the client and provider. Providers that deliver lower quality than promised get penalized by a sufficient amount, such that cheating is strictly uneconomical. This leaves the problem of monitoring the actually delivered quality of service (QoS), a problem addressed by the current project.


Instead of relying on a trusted third party to centrally monitor the quality delivered by the service providers, we propose a distributed approach where the clients themselves give feedback about the service that was delivered to them. Assuming that a large enough group of clients receive the service in the same conditions (i.e. the provider does not discriminate between clients), their aggregated feedback correctly estimates the delivered QoS.

We use a reputation mechanism to collect and aggregate the feedback received from the clients. The novelty of our approach is to also use payments to reward clients for their submitted feedback. Game theoretic results show that it is possible to scale the payments in such a way that clients are motivated to report the truth.

Project Goals

  1. Implement a reputation mechanism that communicates with clients and providers in a service-oriented market.
    • use web services technologies to enable the communication between providers, clients and the reputation mechanism
    • Implement different payment schemes
    • Implement different feedback aggregation rules

  2. Design an automated reporting mechanism for clients (i.e. the monitoring software that can be distributed to clients to automatically submit feedback)

  3. Build a test provider, several test clients and simulate the interactions between clients and provider, and between clients and the reputation mechanism


Java, English


OS independent

Radu Jurca
Last modified: Dec 15, 2005