The exsl:object-type function returns a string giving the type of the object passed as the argument. The possible object types are: 'string', 'number', 'boolean', 'node-set', 'RTF' or 'external'. Most XSLT object types can be coerced to each other without error. However, there are certain coercions that raise errors, most importantly treating anything other than a node set as a node set. Authors of utilities such as named templates or user-defined extension functions may wish to give some flexibility in the parameter and argument values that are accepted by the utility; the exsl:object-type function enables them to do so.