+Try to catch libxml2/libxslt errors and log..
+
+Proxy doesn't do well, if preferredRecordSyntax is not set.
+
Per database config.
Control the various optimizations with config..
Possible threading.
-Deal with Z39.50 options properly.
-
Deal with Z39.50 messages sizes properly.
Character set conversion for SRW queries.
Honor XPath.
-Deal with scan, sort (throw diagnostic).
-