Glossary for Geospatial Science

expression: A line in a query or script that compares values.  An expression evaluates to “true” (1) or “false” (0).  Example: numlines < 3.  It compares the numlines variable for the current node element with the number 3.  The expression is true only if the value of numlines is less than three.  Also, an expression can evaluate to a number (for example: 2*YIELD).  If such an expression is used where true and false values are needed, 0 is treated as false, and anything else is treated as true.