A SAAT tree can be mapped to a SNAT tree, and therefore it implies a precisely defined document to document transformation:
Propagation of the source context is derived from source alignments according to the shortest-path-principle; this enables populating the SNAT metadata related to context propagation (@ctxt, @for-each, @src)
Distribution of the propagated source context over target instances is decided by a default rule (one target instance per instance of the source context, unless the maximum cardinality of the target is one); SNAT metadata @group-by and @sort-by are not used
Atomization of the source context is decided by a default rule (string values of all context nodes are concatenated, using a blank as separator)
No matter how sensible the defaults are, they are only defaults, meeting the actual requirements in some cases and not meeting them in others. A minimal SAAT does define a transformation precisely, but it cannot be used for expressing arbitrary transformations.