BR-FXEXT-06

For each item (BG-25), if the "ID of the parent line" (BT-X-304) is used, the "Subtype of the invoice item" (BT-X-8) must be specified.

error: the document is invalid

What the rule checks

As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.

Context
//ram:IncludedSupplyChainTradeLineItem
Test
normalize-space(ram:AssociatedDocumentLineDocument/ram:ParentLineID) ='' or (normalize-space(ram:AssociatedDocumentLineDocument/ram:ParentLineID) != '' and ram:AssociatedDocumentLineDocument/ram:LineStatusReasonCode != '')

Checked with France Factur-X EXTENDED, Factur-X / ZUGFeRD EXTENDED