The type of questions that can be answered in a GIS can be categorised into:

• What are the data?
  
  
• What are the patterns in the data?
  
  
• What could the data be in another place or time or under different conditions

The answers from a GIS fall into one of three types:

• A presentation of the current data
  
  
• A pattern in the current data
  
  
• A prediction of what the data could be at a different time or place

The three function types used to generate these answers from GIS are:

• Storage and retrieval functions
  
  
• Constrained query functions
  
  
• Modelling functions