Most service level agreements for complex services specify a set of rules and statements which are based particularly on experiences of provider and customer. This very informal procedure does not help in fulfilling the raised requirements. It is very difficult to write high quality SLAs, if there is no structure or methodology guiding the design process.
An approach for specifying SLAs in federated environments is presented in [#!bsc99!#]. A service consists of several components. For each component quality metrics and interdependencies to other components can be specified. This straightforward approach allows to verify the service quality by evaluating relations of measured values provided by each component. The focus lies on service implementation. This complicates the use for complex services because customers are not interested in the numerous measured values of components implementing the service. The implementation view is useful for providers but too difficult to understand for customers which are not familiar with the possible service implementations. Furthermore, this approach does not support management from the customer's domain.
The service model used by the IETF in [#!rfc2758!#] focuses on the service implementation view, too. This RFC defines managed objects which allow the monitoring of service level agreements. The service level is modeled as a set of rules registered in a MIB. The violation of a rule is propagated by SNMP traps. This work focuses on monitoring the service implementation but does not cover the complete management of the service.
Another approach defines a model of electronic services for long-term relationships between customer and provider [#!prko98!#]. SLAs are negotiated between customer and provider to guarantee the availability of a service for repeated use in an open service market where one-time service usage dominates. The approach is based on virtual resources which represent the interface between customer and provider. They are mapped to physical resources on service usage. This approach specifies the interface between customer and provider hiding the service implementation but still focusing solely on the service usage. Interactions not concerned with usage like problem handling are not considered.
There also exists some work of the TeleManagement Forum on processes needed to manage telecommunication services [#!smart-tmn-tom99!#]. The main focus in not the creation of SLAs but the automation of business processes. After completion this standardization effort can simplify the specification of SLAs.
No work for service level agreement specification regarding the interactions which support usage and management of services from the customer's perspective is known. The approach presented in this paper uses workflow concepts to support usage and management of services from the customer's domain and to enable a systematic design of SLAs.