d the customer. Product-specific KQIs derive some of their data from the lower level service KQIs, with service KQIs focused on monitoring the performance of individual product components/services. In its simplest form, a KQI may have a single KPI as its data source. Usually, a service KQI will aggregate several KPIs to calculate the service element quality, and the product KQIs will aggregate multiple service KQIs. Figure 7.8 describes the key indicator hierarchy. The most obvious use for KQIs is to calculate SLA compliance. Usually, multiple KQIs will be used in the SLA management processes. Service KQIs typically support OSS for Telecom Networks Table 7.1 Key indicators versus SLA handbook. From TMF SLA Handbook Service decomposition example Key indicator Customer Residential Basic SOHO Basic SOHO PRO Internet Internet Internet Basic Premium Residential SOHO PRO Web Hosting Web Hosting Internal Email Email Access Access Access Silver SKQIs Elements Email IP Access Web Hosting Service Service Service Email Authentication Access Network Server Server Server Device Elements Server multiple internal or supplier/partner SLAs and product KQIs typically support mul- tiple external or customer SLAs. A service element may depend on a number of network resources and SO a service KQI may call upon multiple KPIs in the aggregation process. The nature of services that may be included in products offered by service providers is likely to result in variants of a basic service. Therefore, it is important that any given KQI can utilise other KQIs as part of its aggregation algorithm. Additional contextual information is used to complete the aggregation process. For example, it should be possible to add weighting factors to reflect the relative import- ance of each KQI parameter. To summarise, starting from network elements, the network performance data are aggregated to provide KPIs that indicate service resource performance. Decomposition of the KPI provides the information that is necessary to identify the individual service