1. A method of modeling and monitoring a computer service, comprising: (a) defining a set of services that said computer service depends upon, wherein said set of services has at least one member; (b) constructing a model of the relationships between the members of said set of services and said computer service, said model identifying a set of measurements for each member of said set of services that gives an indication of the performance of that service, said model including threshold values associated with said measurements; (c) deploying a measurement agent that takes a measurement that is a member of said set of measurements; (d) producing, based on said step (c), a measured performance parameter value indicative of said performance; (e) comparing said measured performance parameter value to one of said threshold values; and (f) determining which member of said set of services is causing abnormal performance of said computer service based on said model and based on said step (e).