# -16041 AN IMPLICIT OR EXPLICIT INVOCATION OF THE fn:boolean FUNCTION IN THE XQUERY EXPRESSION COULD NOT COMPUTE THE EFFECTIVE BOOLEAN VALUE OF THE SEQUENCE. ERROR QNAME=err:FORG0006

#### Explanation

The effective boolean value of the argument passed to fn:boolean could not be computed. The effective boolean value can be computed only if the sequence operand is one of the following sequences:

- An empty sequence
- A sequence where the value of the first item is a node
- A singleton sequence with a value of type xs:string, xdt:untypedAtomic or a type derived from one of these types
- A singleton sequence with a value of any numeric type or derived from any numeric type

#### System action

The XQuery expression is not processed.

#### User response

#### Programmer response

Determine the possible expressions within the XQuery expression where an effective boolean value is calculated either implicitly or explicitly. An implicit invocation of the fn:boolean function can occur when processing the following types of expressions:

- The logical expressions AND and OR
- An fn:not function invocation
- The WHERE clause of an FLWOR expression
- Certain types of predicates, such as a[b]
- Conditional expressions, such as IF

Ensure that the sequence operand of each effective boolean value calculation has a valid sequence operand, as described in the explanation.

#### SQLSTATE

10608