1. Meeting QoS Requirements

2. The Problem Trend is that systems are now distributed across organisational boundaries. QoS is therefore dependent on multiple providers. SLA’s agreed with provider need to be mitigated across different organisations/providers. Current SOA standards focus on functionality, also need QoS standards. Assertion is that testing alone is insufficient as it depends on things outside one provider’s control. A test that passes today may fail tomorrow if the service comes from a different provider.

3. Questions 1.Compositionality How to integrate SLAs into languages such as BPEL? Can SLA’s be composed together. 2.Are SLA parameters safe? Can we architect our systems based on SLAs? 3.Does the candidate architecture live up to the SLA? How to integrate SLA’s with performance testing? Can test cases be derived from SLA’s?

4. Observations SLAs can only be applied to ‘observable’ behaviour. The whole end-to-end business process needs to be understood and SLAs distributed accordingly (like a performance budget). The process needs to ensure that QoS contracts be written at the right time. However some things cannot be known early on and the process needs to be iterative to handle this. Subcontracting means the SI provider must ‘own’ the architecture. They are responsible for this. Assertion is that new activities are required in the development process to derive these SLAs. For example there may need to be a risk assessment done to mitigate against risk of an SLA not being written.

5. Observations Not getting the commercial aspects of SLAs correct can have unforeseen consequences. Example from the commercial world was that trains are often cancelled rather than them being late as it’s cheaper that way. Some work has been done on verification via timed automata. Can SLAs be composed together. Yes probably but SLA depends on how the services themselves are composed. Is there enough information available to do this? Dealing with SLAs properly affects the way we architect systems and how we compose services. Some research starting to be done on this.

6. Areas for Collaboration? Work on standards around web service SLAs. Could IBM provide some SLAs that can be analysed by Wolfgang’s team? Work together on composition of SLAs. Is there a process that flows from this (i.e. that takes into account feedback from operational systems)?