Why are data dimensions the keys to viewing data?

When you create a data set, you specify standard data dimensions, which indicate the additional information that will be saved when study data is collected. Data dimensions are the keys to the data. The way the keys are defined determines how you can view the data that is collected.

For example, a Vital signs data set contains several data series, including Weight. After data is collected, the Weight data series provides the weight values that were recorded in the study. The data series does not include context information, such as identifying information for the subject and the study event in which weight was recorded. To provide this information, you can specify standard data dimensions for a data set.