Message

Only one attachment may be identified as main image.

Context
//cac:CatalogueLine/cac:Item
Test
(count(cac:ItemSpecificationDocumentReference[cbc:DocumentTypeCode = 'main_image']) <= 1)
Usage
/ ubl:Catalogue / cac:CatalogueLine / cac:Item / cac:ItemSpecificationDocumentReference / cbc:DocumentTypeCode