diff --git a/xproc/src/main/xml/specification.xml b/xproc/src/main/xml/specification.xml
index 78173c420..7fdf7dd2d 100644
--- a/xproc/src/main/xml/specification.xml
+++ b/xproc/src/main/xml/specification.xml
@@ -6609,6 +6609,15 @@ error and implementations must take the necessary steps to avoid infinite loops
and/or incorrect notification of duplicate step definitions. An example of such
steps is listed in .
+In some URI schemes, it is possible for different URIs to identify “the
+same” resource. Consider, for example, file:/path/file and
+file:/path/to/../file. To the extent practical, implementations
+should attempt to resolve these differences before deciding
+if a particular library URI has already been imported. Note that this is distinct
+from the case where two genuinely different URIs happen to resolve to the same
+document. The processor isn’t expected to detect that case and errors are likely.
+
+