Before we explore scenario management further, a few key terms should be defined:

• Property—A property is a fundamental characteristic of a model element, and is often a single numeric quantity. For example, the properties of a pipe include diameter, length, and roughness.
• Alternative—An alternative holds a family of related proprties so pieces of data that you are most likely to change together are grouped for easy referencing and editing. For example, a physical properties alternative groups physical data for the network's elements, such as elevations, sizes, and roughness coefficients.
• Scenario—A scenario has a list of referenced alternatives (which hold the attributes), and combines these alternatives to form an overall set of system conditions that can be analyzed. A scenario essentially points to the alternative which contain the propertiy.This referencing of alternatives enables you to easily generate system conditions that mix and match groups of data that have been previously created. Note that scenarios do not actually hold any attribute data—the referenced alternatives do.