Editing Data warehouse (section)

===Facts===
A fact is a value or measurement in the system being managed.

Raw facts are ones reported by the reporting entity. For example, in a mobile telephone system, if a [[base transceiver station]] (BTS) receives 1,000 requests for traffic channel allocation, allocates for 820, and rejects the rest, it could report three facts to a management system:
* {{code|tch_req_total {{=}} 1000}}
* {{code|tch_req_success {{=}} 820}}
* {{code|tch_req_fail {{=}} 180}}

Raw facts are aggregated to higher levels in various [[Dimension (data warehouse)|dimensions]] to extract information more relevant to the service or business. These are called aggregated facts or summaries.

For example, if there are three BTSs in a city, then the facts above can be aggregated to the city level in the network dimension. For example:

* {{code|tch_req_success_city {{=}} tch_req_success_bts1 + tch_req_success_bts2 + tch_req_success_bts3}}
* {{code|avg_tch_req_success_city {{=}} (tch_req_success_bts1 + tch_req_success_bts2 + tch_req_success_bts3) / 3}}