Collects information for potential cross reference targets Processing the root element in the collect.targets mode produces a set of target database elements that can be used by the olink mechanism to resolve external cross references. The collection process is controlled by the collect.xref.targets parameter, which can be yes to collect targets and process the document for output, only to only collect the targets, and no (default) to not collect the targets and only process the document. A targets.filename parameter must be specified to receive the output if collect.xref.targets is set to yes so as to redirect the target data to a file separate from the document output. Must specify a $targets.filename parameter when $collect.xref.targets is set to 'yes'. The xref targets were not collected.