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A RangeCheck defines a constraint on the value of the enclosing item. It represents an expression that evaluates to True when the ItemData value is valid or False when the ItemData value is invalid. The expression is specified using either Comparator and CheckValue or using FormalExpressions.

Range Checks using Comparator and CheckValue

When using Comparator and CheckValue, each range check represents a one-sided constraint. Multiple range checks can be used to specify more complex constraints (e.g., an upper and lower bound would require 2 range checks).

Each constraint is equivalent to:

itemValue comparator checkValue(s)

If an actual data value fails the constraint, it is either rejected (a hard constraint) or a warning is produced (a soft constraint).

For the following comparison operators, one check value is required.

A set of check values is required for these comparators:

If an associated unit with a measurement variable is specified, the corresponding Item values must reflect the values using the associated units specified. Refer to ItemRef/@UnitsItemOID. Proper conversion of units must be done as part of the range check.

Range Checks using FormalExpression

When using FormalExpression a range check can represent anything (e.g., one-sided or multisided checks). These type of checks must not provide CheckValue or Comparator as they would all be expressed in the FormalExpression itself. The FormalExpression takes the value of the ItemData element and returns a boolean value which is the result of the expression. Multiple FormalExpressions can be provided if each has a different Context attribute, allowing the same expression to be represented in forms appropriate to multiple systems. Multiple different expressions, with different meanings, must be represented as separate RangeChecks