-DOCFILE=${DOCFILE_BASE}.${DOCFILE_EXT}
-FOFILE=${DOCFILE_BASE}.fo
-PDFFILE=${DOCFILE_BASE}.pdf
-PSFILE=${DOCFILE_BASE}.ps
-DVIFILE=${DOCFILE_BASE}.dvi
-TXTFILE=${DOCFILE_BASE}.txt
-TMPFILES=${DOCFILE_BASE}.aux ${DOCFILE_BASE}.out ${DOCFILE_BASE}.log
-DOCFILES=$(shell echo *.xml)
+DOCFILE:=${DOCFILE_BASE}.${DOCFILE_EXT}
+FOFILE:=${DOCFILE_BASE}.fo
+PDFFILE:=${DOCFILE_BASE}.pdf
+PSFILE:=${DOCFILE_BASE}.ps
+DVIFILE:=${DOCFILE_BASE}.dvi
+TXTFILE:=${DOCFILE_BASE}.txt
+HTMLFILE:=${DOCFILE_BASE}.html
+TMPFILES:=${DOCFILE_BASE}.aux ${DOCFILE_BASE}.out ${DOCFILE_BASE}.log
+DOCFILES:=$(shell echo *.xml *.xsl)
+
+ifeq ($(XSLTPROC),)
+ XSLTPROC:=xsltproc
+endif
+
+CATALOG:=`pwd`/catalog-${OS}.xml
+CHECK:=XML_CATALOG_FILES="$(CATALOG)" xmllint --noout --xinclude --postvalid $(DOCFILE) || exit 1