What is a Scenario?
  
  An analysis contains one or more scenarios. Each scenario represents a different 
  decision-making alternative. The first scenario in your analysis is called the 
  base scenario. It can represent existing conditions, the primary proposal under 
  evaluation, business as usual, or the first of several alternatives you wish 
  to compare in an analysis.
 What is an Assumption?
  
  An assumption is a value that is used as input to an analysis. They are usually 
  changeable and apply to an entire scenario. Assumptions can be a way to express 
  subjective inputs, such as how much weighting to give to a particular community 
  value like open space or economic development.
 What is an Indicator?
  
  Indicators are impact or performance measures that help people choose alternatives 
  that best match their objectives or desired outcomes. An indicator is a calculated 
  value that represents the impacts or outcomes of a scenario. An indicator might 
  be used to evaluate costs, revenues, average household size, "community benefit", 
  or total daily auto trips. 
 What is an Attribute?
  
  A piece of information describing a map feature. The attributes of a census 
  tract, for example, might include its area, population, and average per capita 
  income. Attributes can also be a characteristic of a geographic feature described 
  by numbers, characters, images, and CAD drawings. For example, the attributes 
  of a well might include depth and gallons per minute. 
 
 What is an Alert?
  
  An alert is used to monitor values during analysis and report if specific conditions 
  occur. Alerts may be displayed as a chart with (colored) target bars, an alert 
  message, or as a feature color on a map. An alert may be associated with an 
  assumption, a dynamic attribute, or an indicator.