the SLO, an EvaluationEvent is defined as the measure by which the SLO will be checked to see if it's meeting the Expression. SLOs should generally be specified in terms of an achievement value or service level, a target measurement, a measurement period, and where and how they are measured. As an example, "90% of calls to the helpdesk should be answered in less than 20 seconds measured over a one-month period as reported by the ACD system". Results can be reported as a percent of time that the target answer time was achieved and then compared to the desired service level (90%). Term usage The SLO term is found in various scientific papers, for instance in the reference architecture of the SLA@SOI project, and it is used in the Open Grid Forum document on WS-Agreement. References IT service management Outsourcing