Language reference : Attributes : Complex attribute definitions : The scope attribute
The scope attribute
The scope attribute identifies the closeness of the relationship between the current document and the target resource.
Set scope to local when the resource is part of the current set of content.
Set scope to peer when the resource is part of the current set of content but is not accessible at build time. An implementation may choose to open such resources in the same browser window to distinguish them from those with scope set to external.
Set scope to external when the resource is not part of the current information set and should open in a new browser window.
See Using the -dita-use-conref-target value for more information on -dita-use-conref-target.
If no value is specified, but the attribute is specified on an ancestor within a map or within the related-links section, the value will cascade from the closest ancestor. The processing default is local.