The primary data query component in RAPID, the HDA server, supports the concept of aggregation of data. For instance you can ask a query such as ‘return the average value for tag x over the last 24 hours’ and the HDA server will return a single value that is the average of all logged data for that tag for the last 24 hours. This can be extended to request 1 value for each hour, or each minute. The supported set of aggregates are compliant with the OPC HDA specification. For greater flexibility it is also possible to apply filters, for instance, to only use good quality data or only data within a range as the input to the aggregate calculation.