1. A method, comprising: deriving a value for each of a plurality of key performance indicators (KPIs), each KPI indicating a different aspect of how a same service provided by one or more entities is performing at a point in time or during a period of time, each KPI defined by a search query that derives the value for that KPI from machine data associated with the one or more entities that provide the same service, each of the one or more entities having a respective entity definition including information to identify the machine data associated with the respective entity, and the same service having a service definition associating each of the entity definitions; and determining a value for an aggregate KPI for the same service from the values for each of the plurality of KPIs, wherein the machine data is produced by one or more components within an information technology environment and reflects activity within the information technology environment; wherein the method is performed by a computer system comprising one or more processing devices.