diff --git a/C/init.c b/C/init.c
index b26c51cae..790b86fb1 100755
--- a/C/init.c
+++ b/C/init.c
@@ -1346,11 +1346,11 @@ Yap_InitWorkspace(UInt Heap, UInt Stack, UInt Trail, UInt Atts, UInt max_table_s
     Yap_Error(INTERNAL_ERROR, TermNil, "excessive number of workers (Yap_InitWorkspace)");
 #ifdef YAPOR_COPY
   INFORMATION_MESSAGE("YapOr: copy model with %d worker%s", n_workers, n_workers == 1 ? "":"s");
-#elif ACOW
+#elif YAPOR_COW
   INFORMATION_MESSAGE("YapOr: acow model with %d worker%s", n_workers, n_workers == 1 ? "":"s");
 #else /* YAPOR_SBA */
   INFORMATION_MESSAGE("YapOr: sba model with %d worker%s", n_workers, n_workers == 1 ? "":"s");
-#endif /* YAPOR_COPY - ACOW - YAPOR_SBA */
+#endif /* YAPOR_COPY - YAPOR_COW - YAPOR_SBA */
   map_memory(Heap, Stack+Atts, Trail, n_workers);
 #else
   Yap_InitMemory (Trail, Heap, Stack+Atts);
diff --git a/C/sysbits.c b/C/sysbits.c
index b8c29b44f..fa88905fa 100755
--- a/C/sysbits.c
+++ b/C/sysbits.c
@@ -1830,7 +1830,7 @@ InitSignals (void)
 #if HAVE_SIGSEGV && !defined(THREADS) 
     my_signal_info (SIGSEGV, HandleSIGSEGV);
 #endif
-#ifdef ACOW
+#ifdef YAPOR_COW
     signal(SIGCHLD, SIG_IGN);  /* avoid ghosts */ 
 #endif
   } else {
diff --git a/H/Yap.h b/H/Yap.h
index 097837be2..ff679772f 100755
--- a/H/Yap.h
+++ b/H/Yap.h
@@ -39,22 +39,22 @@
 #error Do not explicitly define YAPOR
 #endif /* YAPOR */
 
-#if (defined(YAPOR_COPY) && (defined(ACOW) || defined(YAPOR_SBA))) || (defined(ACOW) && defined(YAPOR_SBA))
+#if (defined(YAPOR_COPY) && (defined(YAPOR_COW) || defined(YAPOR_SBA))) || (defined(YAPOR_COW) && defined(YAPOR_SBA))
 #error Do not define multiple or-parallel models
-#endif /* (YAPOR_COPY && (ACOW || YAPOR_SBA)) || (ACOW && YAPOR_SBA) */
+#endif /* (YAPOR_COPY && (YAPOR_COW || YAPOR_SBA)) || (YAPOR_COW && YAPOR_SBA) */
 
-#if defined(YAPOR_COPY) || defined(ACOW) || defined(YAPOR_SBA) || defined(THREADS)
+#if defined(YAPOR_COPY) || defined(YAPOR_COW) || defined(YAPOR_SBA) || defined(THREADS)
 #define YAPOR 1
-#endif /* YAPOR_COPY || ACOW || YAPOR_SBA */
+#endif /* YAPOR_COPY || YAPOR_COW || YAPOR_SBA */
 
-#if defined(TABLING) && (defined(ACOW) || defined(YAPOR_SBA))
+#if defined(TABLING) && (defined(YAPOR_COW) || defined(YAPOR_SBA))
 #error Currently TABLING only works with YAPOR_COPY
-#endif /* TABLING && (ACOW || YAPOR_SBA) */
+#endif /* TABLING && (YAPOR_COW || YAPOR_SBA) */
 
 #ifdef YAPOR
 #define FIXED_STACKS 1
 #ifdef THREADS
-#undef ACOW
+#undef YAPOR_COW
 #undef YAPOR_SBA
 #undef YAPOR_COPY
 #endif
diff --git a/H/amidefs.h b/H/amidefs.h
index b4ace430d..13a09dd22 100644
--- a/H/amidefs.h
+++ b/H/amidefs.h
@@ -998,7 +998,7 @@ typedef struct choicept {
 #define YOUNGER_H(H1, H2) FIXMEE!!!!
 
 
-#else /* YAPOR_COPY || ACOW */
+#else /* YAPOR_COPY || YAPOR_COW */
 #define YOUNGER_CP(CP1, CP2)           ((CP1) <  (CP2))
 #define EQUAL_OR_YOUNGER_CP(CP1, CP2)  ((CP1) <= (CP2))
 
diff --git a/INSTALL b/INSTALL
index 1014c8124..08e27fcc0 100644
--- a/INSTALL
+++ b/INSTALL
@@ -62,7 +62,7 @@ quality:
 
   o -DYAPOR gives or-parallelism in Muse style. If you add -DSBA to it
 you will have the Sparse Binding Array instead of copying. If you add
--DACOW instead you will have the \alphaCOW model, that is, forking
+-DYAPOR_COW instead you will have the \alphaCOW model, that is, forking
 instead of copying.
 
 1.3 Porting Yap
diff --git a/Makefile.in b/Makefile.in
index e26a1e9c0..6b2d6d62f 100755
--- a/Makefile.in
+++ b/Makefile.in
@@ -44,7 +44,7 @@ DOCSDIR=$(SHAREDIR)/doc/Yap
 # if you want to use this:
 #       -DYAPOR_COPY: or-parallelism with environment copying, in Muse style.
 #       -DYAPOR_SBA: or-parallelism with sparse binding arrays.
-#       -DACOW: or-parallelism with copy-on-write.
+#       -DYAPOR_COW: or-parallelism with copy-on-write.
 #       -DTABLING: support for tabling
 #
 #
diff --git a/OPTYap/opt.init.c b/OPTYap/opt.init.c
index e90857070..9773bf725 100644
--- a/OPTYap/opt.init.c
+++ b/OPTYap/opt.init.c
@@ -28,7 +28,7 @@
 #ifdef TABLING
 #include "tab.macros.h"
 #endif /* TABLING */
-#if defined(TABLING) || !defined(ACOW)
+#if defined(TABLING) || !defined(YAPOR_COW)
 #ifndef TABLING
 #include "opt.mavar.h"
 #endif /* !TABLING */
@@ -37,10 +37,10 @@ ma_hash_entry Yap_ma_hash_table[MAVARS_HASH_SIZE];
 UInt Yap_timestamp;    /* an unsigned int */
 ma_h_inner_struct *Yap_ma_h_top;
 #endif /* MULTI_ASSIGNMENT_VARIABLES */
-#endif /* TABLING || !ACOW */
-#ifdef ACOW
+#endif /* TABLING || !YAPOR_COW */
+#ifdef YAPOR_COW
 #include "sys/wait.h"
-#endif /* ACOW */
+#endif /* YAPOR_COW */
 
 
 
@@ -255,7 +255,7 @@ void init_workers(void) {
 #ifdef THREADS
   return;
 #endif
-#ifdef ACOW
+#ifdef YAPOR_COW
   if (Yap_number_workers> 1) {
     int son;
     son = fork();
@@ -274,7 +274,7 @@ void init_workers(void) {
       exit(0);
     } else Yap_worker_pid(0) = getpid();
   }
-#endif /* ACOW */
+#endif /* YAPOR_COW */
   for (proc = 1; proc < Yap_number_workers; proc++) {
     int son;
     son = fork();
diff --git a/OPTYap/opt.memory.c b/OPTYap/opt.memory.c
index fc17ecc3b..d7dadb103 100644
--- a/OPTYap/opt.memory.c
+++ b/OPTYap/opt.memory.c
@@ -82,7 +82,7 @@ close_mapfile(void) {
 
 void map_memory(long HeapArea, long GlobalLocalArea, long TrailAuxArea, int n_workers) {
   void *mmap_addr = (void *)MMAP_ADDR;
-#ifdef ACOW
+#ifdef YAPOR_COW
   int private_fd_mapfile;
 #if MMAP_MEMORY_MAPPING_SCHEME
   long TotalArea;
@@ -108,7 +108,7 @@ void map_memory(long HeapArea, long GlobalLocalArea, long TrailAuxArea, int n_wo
   Yap_GlobalBase = mmap_addr + HeapArea;
 
   /* shared memory allocation - model dependent */
-#ifdef ACOW
+#ifdef YAPOR_COW
   /* acow just needs one stack */
 #ifdef MMAP_MEMORY_MAPPING_SCHEME
   /* I need this for MMAP to know what it must allocate */
@@ -131,7 +131,7 @@ void map_memory(long HeapArea, long GlobalLocalArea, long TrailAuxArea, int n_wo
 #endif
 #else /* SHM_MEMORY_MAPPING_SCHEME */
 /* Most systems are limited regarding what we can allocate */
-#ifdef ACOW
+#ifdef YAPOR_COW
   /* single shared segment in ACOW */
   shm_map_memory(0, HeapArea, mmap_addr);
 #else /* YAPOR_COPY || YAPOR_SBA */
@@ -140,7 +140,7 @@ void map_memory(long HeapArea, long GlobalLocalArea, long TrailAuxArea, int n_wo
 #endif /* YAPOR_MODEL */
 #endif /* MEMORY_MAPPING_SCHEME */
 
-#ifdef ACOW
+#ifdef YAPOR_COW
   /* just allocate local space for stacks */
   if ((private_fd_mapfile = open("/dev/zero", O_RDWR)) < 0)
     Yap_Error(FATAL_ERROR, TermNil, "open error (map_memory)");
@@ -201,22 +201,22 @@ void unmap_memory (void) {
           INFORMATION_MESSAGE("Killing process %d", Yap_worker_pid(proc));
       }
     }
-#ifdef ACOW
+#ifdef YAPOR_COW
     if (Yap_number_workers > 1) {
       if (kill(Yap_master_worker, SIGINT) != 0)
 	INFORMATION_MESSAGE("Can't kill process %d", Yap_master_worker);
       else 
 	INFORMATION_MESSAGE("Killing process %d", Yap_master_worker);
     }
-#endif /* ACOW */
+#endif /* YAPOR_COW */
   }
 
 #ifdef SHM_MEMORY_MAPPING_SCHEME
-#ifdef ACOW
+#ifdef YAPOR_COW
   i = 0;
 #else
   for (i = 0; i < Yap_number_workers + 1; i++)
-#endif /* ACOW */
+#endif /* YAPOR_COW */
   {
     if (shmctl(shm_mapid[i], IPC_RMID, 0) == 0)
       INFORMATION_MESSAGE("Removing shared memory segment %d", shm_mapid[i]);
@@ -224,7 +224,7 @@ void unmap_memory (void) {
   }
 #else /* MMAP_MEMORY_MAPPING_SCHEME */
   strcpy(MapFile,"./mapfile");
-#ifdef ACOW
+#ifdef YAPOR_COW
   itos(Yap_master_worker, &MapFile[9]);
 #else /* YAPOR_COPY || YAPOR_SBA */
   itos(Yap_worker_pid(0), &MapFile[9]);
@@ -238,9 +238,9 @@ void unmap_memory (void) {
 
 
 void remap_memory(void) {
-#ifdef ACOW
+#ifdef YAPOR_COW
   /* do nothing */
-#endif /* ACOW */
+#endif /* YAPOR_COW */
 #ifdef YAPOR_SBA
   /* setup workers so that they have different areas */
   long WorkerArea = worker_offset(1);
diff --git a/OPTYap/opt.structs.h b/OPTYap/opt.structs.h
index 059152be2..527b28b41 100644
--- a/OPTYap/opt.structs.h
+++ b/OPTYap/opt.structs.h
@@ -170,9 +170,9 @@ struct optyap_global_data{
   int delayed_release_load;
   int number_workers;
   int worker_pid[MAX_WORKERS];
-#ifdef ACOW
+#ifdef YAPOR_COW
   int master_worker;
-#endif /* ACOW */
+#endif /* YAPOR_COW */
 
   /* global data related to or-performance */
   realtime execution_time;
diff --git a/OPTYap/or.cowengine.c b/OPTYap/or.cowengine.c
index cd52ce7ca..e0c8ba5e8 100644
--- a/OPTYap/or.cowengine.c
+++ b/OPTYap/or.cowengine.c
@@ -16,7 +16,7 @@
 ** ------------------ */
 
 #include "Yap.h"
-#ifdef ACOW
+#ifdef YAPOR_COW
 #include <sys/types.h>
 #include <unistd.h>
 #include <stdio.h>
@@ -230,4 +230,4 @@ void share_private_nodes(int worker_q) {
   REMOTE_load(worker_q) = LOCAL_load = 0;
   return;
 }
-#endif /* ACOW */
+#endif /* YAPOR_COW */
diff --git a/OPTYap/or.macros.h b/OPTYap/or.macros.h
index 2cabcda20..9ee749654 100644
--- a/OPTYap/or.macros.h
+++ b/OPTYap/or.macros.h
@@ -143,13 +143,13 @@ STD_PROTO(static inline qg_sol_fr_ptr CUT_prune_solution_frames, (qg_sol_fr_ptr,
           p_share_work();             \
 	  setregs();                  \
         }
-#else /* ACOW */
+#else /* YAPOR_COW */
 #define SCH_check_share_request()     \
         if (SCH_any_share_request) {  \
           if (! p_share_work())       \
             goto shared_fail;         \
         }
-#endif /* YAPOR_COPY || YAPOR_SBA || ACOW */
+#endif /* YAPOR_COPY || YAPOR_SBA || YAPOR_COW */
 
 #define SCH_check_requests()          \
         SCH_check_prune_request();    \
diff --git a/VC/include/Yap.h b/VC/include/Yap.h
index fcc1806e5..bd2fac09a 100644
--- a/VC/include/Yap.h
+++ b/VC/include/Yap.h
@@ -54,17 +54,17 @@
 #error Do not explicitly define YAPOR
 #endif /* YAPOR */
 
-#if (defined(YAPOR_COPY) && (defined(ACOW) || defined(YAPOR_SBA))) || (defined(ACOW) && defined(YAPOR_SBA))
+#if (defined(YAPOR_COPY) && (defined(YAPOR_COW) || defined(YAPOR_SBA))) || (defined(YAPOR_COW) && defined(YAPOR_SBA))
 #error Do not define multiple or-parallel models
-#endif /* (YAPOR_COPY && (ACOW || YAPOR_SBA)) || (ACOW && YAPOR_SBA) */
+#endif /* (YAPOR_COPY && (YAPOR_COW || YAPOR_SBA)) || (YAPOR_COW && YAPOR_SBA) */
 
-#if defined(YAPOR_COPY) || defined(ACOW) || defined(YAPOR_SBA)
+#if defined(YAPOR_COPY) || defined(YAPOR_COW) || defined(YAPOR_SBA)
 #define YAPOR 1
-#endif /* YAPOR_COPY || ACOW || YAPOR_SBA */
+#endif /* YAPOR_COPY || YAPOR_COW || YAPOR_SBA */
 
-#if defined(TABLING) && (defined(ACOW) || defined(YAPOR_SBA))
+#if defined(TABLING) && (defined(YAPOR_COW) || defined(YAPOR_SBA))
 #error Currently TABLING only works with YAPOR_COPY
-#endif /* TABLING && (ACOW || YAPOR_SBA) */
+#endif /* TABLING && (YAPOR_COW || YAPOR_SBA) */
 
 #ifdef YAPOR
 #define FIXED_STACKS 1
diff --git a/configure b/configure
index 715b6a300..cb0bab7a8 100755
--- a/configure
+++ b/configure
@@ -7495,7 +7495,7 @@ case "$orparallelism" in
    YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_SBA=1"
   ;;
   a-cow)
-   YAP_EXTRAS="$YAP_EXTRAS -DACOW=1"
+   YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_COW=1"
   ;;
   yes|env-copy)
    YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_COPY=1"
diff --git a/configure.in b/configure.in
index 957a7b50e..b4a4fe504 100644
--- a/configure.in
+++ b/configure.in
@@ -1279,7 +1279,7 @@ case "$orparallelism" in
    YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_SBA=1"
   ;;
   a-cow)
-   YAP_EXTRAS="$YAP_EXTRAS -DACOW=1"
+   YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_COW=1"
   ;;
   yes|env-copy)
    YAP_EXTRAS="$YAP_EXTRAS -DYAPOR_COPY=1"
diff --git a/console/yap.c b/console/yap.c
index a251029fb..b404b0502 100644
--- a/console/yap.c
+++ b/console/yap.c
@@ -149,14 +149,14 @@ print_usage(void)
 #ifdef TABLING
   fprintf(stderr,"  -ts  Maximum table space area in Mbytes (default: unlimited)\n");
 #endif /* TABLING */
-#if defined(YAPOR_COPY) || defined(ACOW) || defined(YAPOR_SBA)
+#if defined(YAPOR_COPY) || defined(YAPOR_COW) || defined(YAPOR_SBA)
   fprintf(stderr,"  -w   Number of workers (default: %d)\n",
 	  DEFAULT_NUMBERWORKERS);
   fprintf(stderr,"  -sl  Loop scheduler executions before look for hiden shared work (default: %d)\n", 
           DEFAULT_SCHEDULERLOOP);
   fprintf(stderr,"  -d   Value of delayed release of load (default: %d)\n",
 	  DEFAULT_DELAYEDRELEASELOAD);
-#endif /* YAPOR_COPY || ACOW || YAPOR_SBA */
+#endif /* YAPOR_COPY || YAPOR_COW || YAPOR_SBA */
   /* nf: Preprocessor */		
   /* fprintf(stderr,"  -DVar=Name   Persistent definition\n"); */
   fprintf(stderr,"\n");
@@ -245,7 +245,7 @@ parse_yap_arguments(int argc, char *argv[], YAP_init_args *iap)
           case 'q':
 	    iap->QuietMode = TRUE;
 	    break;
-#if defined(YAPOR_COPY) || defined(ACOW) || defined(YAPOR_SBA)
+#if defined(YAPOR_COPY) || defined(YAPOR_COW) || defined(YAPOR_SBA)
 	  case 'w':
 	    ssize = &(iap->NumberWorkers);
 	    goto GetSize;
@@ -258,7 +258,7 @@ parse_yap_arguments(int argc, char *argv[], YAP_init_args *iap)
           case 'd':
 	    if (!strcmp("dump-runtime-variables",p))
 		return dump_runtime_variables();
-#endif /* YAPOR_COPY || ACOW || YAPOR_SBA */
+#endif /* YAPOR_COPY || YAPOR_COW || YAPOR_SBA */
 #ifdef USE_SOCKET
           case 'c':          /* running as client */
 	    {
@@ -386,12 +386,12 @@ parse_yap_arguments(int argc, char *argv[], YAP_init_args *iap)
 	  case 's':
 	  case 'S':
 	    ssize = &(iap->StackSize);
-#if defined(YAPOR_COPY) || defined(ACOW) || defined(YAPOR_SBA)
+#if defined(YAPOR_COPY) || defined(YAPOR_COW) || defined(YAPOR_SBA)
 	    if (p[1] == 'l') {
 	      p++;
 	      ssize = &(iap->SchedulerLoop);
 	    }
-#endif /* YAPOR_COPY || ACOW || YAPOR_SBA */
+#endif /* YAPOR_COPY || YAPOR_COW || YAPOR_SBA */
 	    goto GetSize;
 	  case 'a':
 	  case 'A':