Amazon CloudWatch
Developer Guide (API Version 2010-08-01)

Amazon CloudWatch Namespaces, Dimensions, and Metrics Reference

This section includes all of the namespaces, dimensions, and metrics that you can use with CloudWatch. Namespaces are containers for metrics. Metrics, which are time-ordered sets of data points, are isolated from one another in different namespaces so that metrics from different applications are not mistakenly aggregated into the same statistics. In addition, each metric has a dimension, which is a name/value pair that helps you to uniquely identify a metric.