How to use the DITA OT build logger
ant -f buildfile target -logger org.dita.dost.log.DITAOTBuildLogger
DITA-OT prints the usual build messages to the console, but also informs you of the name of the log file it generated, as shown in the following figure.
In this example, the log file name is dita-ot-xsl-debugging_PDF.log. DITA-OT appends its internal name for the target, _PDF to the name of your ditamap to name the log file. If the target had been xhtml, the example log file would be named dita-ot-xsl-debugging_xhtml.log. The file contains the same data as the ouput on the console, but you may find it easier to debug xsl transformation errors this way.