diff --git a/Makefile.in b/Makefile.in
index e77d99a0c..7a538b294 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -709,6 +709,7 @@ all: startup.yss
 	@ENABLE_CPLINT@ (cd packages/cplint/approx/simplecuddLPADs; $(MAKE))
 	@ENABLE_CPLINT@ (cd packages/cplint; $(MAKE))
 	@ENABLE_CPLINT@ (cd packages/cplint/slipcase; $(MAKE))
+	@ENABLE_PRISM@ (cd packages/prism/src/c; $(MAKE))
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd; $(MAKE))
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd_lfi; $(MAKE))
 	@ENABLE_JPL@ @INSTALL_DLLS@ (cd packages/jpl; $(MAKE))
@@ -785,6 +786,8 @@ install_unix: startup.yss libYap.a
 	$(INSTALL) YapTermConfig.h $(DESTDIR)$(INCLUDEDIR)
 	@ENABLE_CPLINT@ (cd packages/cplint; $(MAKE) install)
 	@ENABLE_CPLINT@ (cd packages/cplint/approx/simplecuddLPADs; $(MAKE) install)
+	@ENABLE_PRISM@ (cd packages/prism/src/c; $(MAKE) install)
+	@ENABLE_PRISM@ (cd packages/prism/src/prolog; $(MAKE) install)
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd; $(MAKE) install)
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd_lfi; $(MAKE) install)
 
@@ -835,6 +838,8 @@ install_win32: startup.yss @ENABLE_WINCONSOLE@ pl-yap@EXEC_SUFFIX@
 	@ENABLE_JPL@ (cd packages/jpl ; $(MAKE) install)
 	@ENABLE_MINISAT@ (cd packages/swi-minisat2/C; $(MAKE) install)
 	@ENABLE_CPLINT@ (cd packages/cplint; $(MAKE) install)
+	@ENABLE_PRISM@ (cd packages/prism/src/c; $(MAKE) install)
+	@ENABLE_PRISM@ (cd packages/prism/src/prolog; $(MAKE) install)
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd; $(MAKE) install)
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd_lfi; $(MAKE) install)
 
@@ -894,6 +899,8 @@ clean: clean_docs
 	@ENABLE_MINISAT@ (cd packages/swi-minisat2; $(MAKE) clean)
 	@ENABLE_CLPBN_BP@ (cd packages/CLPBN/clpbn/bp; $(MAKE) clean)
 	@ENABLE_ZLIB@ @INSTALL_DLLS@ (cd packages/zlib; $(MAKE) clean)
+	@ENABLE_PRISM@ (cd packages/prism/src/c; $(MAKE) clean)
+	@ENABLE_PRISM@ (cd packages/prism/src/prolog; $(MAKE) clean)
 	@ENABLE_CPLINT@ (cd packages/cplint/approx/simplecuddLPADs; $(MAKE) clean)
 	@ENABLE_CPLINT@ (cd packages/cplint; $(MAKE) clean)
 	@ENABLE_CUDD@ (cd packages/ProbLog/simplecudd; $(MAKE) clean)
diff --git a/configure b/configure
index b44db2e59..4d2109dbd 100755
--- a/configure
+++ b/configure
@@ -615,6 +615,7 @@ IN_SWI
 IN_YAP
 PROLOG_SYSTEM
 M4GENABSMI
+INSTALL_PRISM
 MATLAB_INCLUDE
 INSTALL_MATLAB
 EXTRA_LIBS_FOR_R
@@ -790,6 +791,7 @@ enable_max_memory
 enable_debug_yap
 enable_eam
 enable_cygwin
+enable_prism
 enable_dynamic_loading
 enable_static_compilation
 enable_use_malloc
@@ -1463,6 +1465,7 @@ Optional Features:
  --enable-debug-yap         enable C-debugging for YAP
  --enable-eam               enable EAM on YAP
  --enable-cygwin            use cygwin library in WIN32
+ --enable-prism            use PRISM system in YAP
  --enable-dynamic-loading   compile YAP as a DLL
  --enable-static-compilation   compile YAP statically
  --enable-use-malloc        use malloc to allocate memory
@@ -2528,7 +2531,7 @@ $as_echo "$as_me: loading site script $ac_site_file" >&6;}
       || { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "failed to load site script $ac_site_file
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
   fi
 done
 
@@ -2925,7 +2928,7 @@ fi
 test -z "$CC" && { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "no acceptable C compiler found in \$PATH
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 
 # Provide some information about the compiler.
 $as_echo "$as_me:${as_lineno-$LINENO}: checking for C compiler version" >&5
@@ -3040,7 +3043,7 @@ sed 's/^/| /' conftest.$ac_ext >&5
 { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "C compiler cannot create executables
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
@@ -3083,7 +3086,7 @@ else
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot compute suffix of executables: cannot compile and link
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 fi
 rm -f conftest conftest$ac_cv_exeext
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_exeext" >&5
@@ -3142,7 +3145,7 @@ $as_echo "$ac_try_echo"; } >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot run C compiled programs.
 If you meant to cross compile, use \`--host'.
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
     fi
   fi
 fi
@@ -3194,7 +3197,7 @@ sed 's/^/| /' conftest.$ac_ext >&5
 { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot compute suffix of object files: cannot compile
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 fi
 rm -f conftest.$ac_cv_objext conftest.$ac_ext
 fi
@@ -3774,7 +3777,7 @@ fi
 $as_echo "$ac_cv_build" >&6; }
 case $ac_cv_build in
 *-*-*) ;;
-*) as_fn_error $? "invalid value of canonical build" "$LINENO" 5 ;;
+*) as_fn_error $? "invalid value of canonical build" "$LINENO" 5;;
 esac
 build=$ac_cv_build
 ac_save_IFS=$IFS; IFS='-'
@@ -3807,7 +3810,7 @@ fi
 $as_echo "$ac_cv_host" >&6; }
 case $ac_cv_host in
 *-*-*) ;;
-*) as_fn_error $? "invalid value of canonical host" "$LINENO" 5 ;;
+*) as_fn_error $? "invalid value of canonical host" "$LINENO" 5;;
 esac
 host=$ac_cv_host
 ac_save_IFS=$IFS; IFS='-'
@@ -3840,7 +3843,7 @@ fi
 $as_echo "$ac_cv_target" >&6; }
 case $ac_cv_target in
 *-*-*) ;;
-*) as_fn_error $? "invalid value of canonical target" "$LINENO" 5 ;;
+*) as_fn_error $? "invalid value of canonical target" "$LINENO" 5;;
 esac
 target=$ac_cv_target
 ac_save_IFS=$IFS; IFS='-'
@@ -4013,7 +4016,7 @@ else
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "C preprocessor \"$CPP\" fails sanity check
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 fi
 
 ac_ext=c
@@ -4486,6 +4489,13 @@ else
   cygwin=no
 fi
 
+# Check whether --enable-prism was given.
+if test "${enable_prism+set}" = set; then :
+  enableval=$enable_prism; prism="$enableval"
+else
+  prism=yes
+fi
+
 # Check whether --enable-dynamic_loading was given.
 if test "${enable_dynamic_loading+set}" = set; then :
   enableval=$enable_dynamic_loading; dynamic_loading="$enableval"
@@ -4922,6 +4932,13 @@ _ACEOF
 fi
 
 
+if test "$yap_cv_prism" = no
+then
+  INSTALL_PRISM="@# "
+else
+  INSTALL_PRISM=""
+fi
+
 if test "$yap_cv_matlab" = no
 then
   INSTALL_MATLAB="@# "
@@ -6238,7 +6255,7 @@ else
                  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "--with-readline was given, but test for readline failed
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
                fi
 
 fi
@@ -6990,7 +7007,7 @@ else
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "C preprocessor \"$CPP\" fails sanity check
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 fi
 
 ac_ext=c
@@ -7054,7 +7071,7 @@ else
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot run test program while cross compiling
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
@@ -7660,19 +7677,19 @@ if test "$threads" = "yes"
       { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "--or-parallelism=sba incompatible with threads
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
     ;;
     a-cow)
       { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "--or-parallelism=a-cow incompatible with threads
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
     ;;
     copy)
       { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "--or-parallelism=copy incompatible with threads
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
     ;;
     yes|threads)
      YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_THREADS=1"
@@ -8408,7 +8425,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (int *)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_int_p=0
    fi
@@ -8441,7 +8458,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (short int)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_short_int=0
    fi
@@ -8474,7 +8491,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (int)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_int=0
    fi
@@ -8507,7 +8524,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (long int)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_long_int=0
    fi
@@ -8540,7 +8557,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (long long int)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_long_long_int=0
    fi
@@ -8573,7 +8590,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (float)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_float=0
    fi
@@ -8606,7 +8623,7 @@ else
      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error 77 "cannot compute sizeof (double)
-See \`config.log' for more details" "$LINENO" 5 ; }
+See \`config.log' for more details" "$LINENO" 5; }
    else
      ac_cv_sizeof_double=0
    fi
@@ -8784,6 +8801,7 @@ fi
 
 
 
+
 
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for gcc threaded code" >&5
@@ -10966,7 +10984,7 @@ do
     "packages/prism/src/c/Makefile") CONFIG_FILES="$CONFIG_FILES packages/prism/src/c/Makefile" ;;
     "packages/prism/src/prolog/Makefile") CONFIG_FILES="$CONFIG_FILES packages/prism/src/prolog/Makefile" ;;
 
-  *) as_fn_error $? "invalid argument: \`$ac_config_target'" "$LINENO" 5 ;;
+  *) as_fn_error $? "invalid argument: \`$ac_config_target'" "$LINENO" 5;;
   esac
 done
 
@@ -11283,7 +11301,7 @@ do
   esac
   case $ac_mode$ac_tag in
   :[FHL]*:*);;
-  :L* | :C*:*) as_fn_error $? "invalid tag \`$ac_tag'" "$LINENO" 5 ;;
+  :L* | :C*:*) as_fn_error $? "invalid tag \`$ac_tag'" "$LINENO" 5;;
   :[FH]-) ac_tag=-:-;;
   :[FH]*) ac_tag=$ac_tag:$ac_tag.in;;
   esac
@@ -11311,7 +11329,7 @@ do
 	   [\\/$]*) false;;
 	   *) test -f "$srcdir/$ac_f" && ac_f="$srcdir/$ac_f";;
 	   esac ||
-	   as_fn_error 1 "cannot find input file: \`$ac_f'" "$LINENO" 5 ;;
+	   as_fn_error 1 "cannot find input file: \`$ac_f'" "$LINENO" 5;;
       esac
       case $ac_f in *\'*) ac_f=`$as_echo "$ac_f" | sed "s/'/'\\\\\\\\''/g"`;; esac
       as_fn_append ac_file_inputs " '$ac_f'"
@@ -11338,7 +11356,7 @@ $as_echo "$as_me: creating $ac_file" >&6;}
 
     case $ac_tag in
     *:-:* | *:-) cat >"$ac_tmp/stdin" \
-      || as_fn_error $? "could not create $ac_file" "$LINENO" 5  ;;
+      || as_fn_error $? "could not create $ac_file" "$LINENO" 5 ;;
     esac
     ;;
   esac
diff --git a/configure.in b/configure.in
index 929668adb..6598b1197 100755
--- a/configure.in
+++ b/configure.in
@@ -153,6 +153,9 @@ AC_ARG_ENABLE(eam,
 AC_ARG_ENABLE(cygwin,
 	[ --enable-cygwin            use cygwin library in WIN32 ],
 	cygwin="$enableval", cygwin=no)
+AC_ARG_ENABLE(prism,
+	[ --enable-prism            use PRISM system in YAP ],
+	prism="$enableval", prism=yes)
 AC_ARG_ENABLE(dynamic_loading,
 	[ --enable-dynamic-loading   compile YAP as a DLL ],
 	dynamic_loading="$enableval", dynamic_loading=no)
@@ -453,6 +456,13 @@ else
 fi
 
 
+if test "$yap_cv_prism" = no 
+then
+  INSTALL_PRISM="@# "
+else
+  INSTALL_PRISM=""
+fi
+
 dnl condor does not like dynamic linking on Linux, DEC, and HP-UX platforms.
 if test "$yap_cv_matlab" = no 
 then
@@ -1711,6 +1721,7 @@ AC_SUBST(YAPR_INCLUDES)
 AC_SUBST(EXTRA_LIBS_FOR_R)
 AC_SUBST(INSTALL_MATLAB)
 AC_SUBST(MATLAB_INCLUDE)
+AC_SUBST(INSTALL_PRISM)
 
 dnl check for threaded code
 AC_MSG_CHECKING(for gcc threaded code)