diff --git a/mps/code/mpm.h b/mps/code/mpm.h
index 5153d381a1c..5ce72628faa 100644
--- a/mps/code/mpm.h
+++ b/mps/code/mpm.h
@@ -18,6 +18,7 @@
 
 #include "event.h"
 #include "lock.h"
+#include "prmc.h"
 #include "prot.h"
 #include "sp.h"
 #include "th.h"
diff --git a/mps/code/mps.c b/mps/code/mps.c
index a6d1876c80f..1631f8fc781 100644
--- a/mps/code/mps.c
+++ b/mps/code/mps.c
@@ -106,7 +106,7 @@
 #include "than.c"       /* generic threads manager */
 #include "vman.c"       /* malloc-based pseudo memory mapping */
 #include "protan.c"     /* generic memory protection */
-#include "prmcan.c"     /* generic protection mutator context */
+#include "prmcan.c"     /* generic mutator context */
 #include "span.c"       /* generic stack probe */
 #include "ssan.c"       /* generic stack scanner */
 
diff --git a/mps/code/poolabs.c b/mps/code/poolabs.c
index 0efc8a36a61..703937ef58a 100644
--- a/mps/code/poolabs.c
+++ b/mps/code/poolabs.c
@@ -494,7 +494,7 @@ Res PoolSingleAccess(Pool pool, Seg seg, Addr addr,
 
   arena = PoolArena(pool);
 
-  if(ProtCanStepInstruction(context)) {
+  if (MutatorContextCanStepInstruction(context)) {
     Ref ref;
     Res res;
 
@@ -517,7 +517,7 @@ Res PoolSingleAccess(Pool pool, Seg seg, Addr addr,
                            seg, (Ref *)addr);
       }
     }
-    res = ProtStepInstruction(context);
+    res = MutatorContextStepInstruction(context);
     AVER(res == ResOK);
 
     /* Update SegSummary according to the possibly changed reference. */
diff --git a/mps/code/prmc.h b/mps/code/prmc.h
new file mode 100644
index 00000000000..22247154493
--- /dev/null
+++ b/mps/code/prmc.h
@@ -0,0 +1,68 @@
+/* prmc.h: MUTATOR CONTEXT INTERFACE
+ *
+ * $Id$
+ * Copyright (c) 2016 Ravenbrook Limited.  See end of file for license.
+ *
+ * See <design/prmc/> for the design of the generic interface including
+ * the contracts for these functions.
+ *
+ * This interface has several different implementations, typically one
+ * per platform, see <code/prmc*.c> for the various implementations.
+ */
+
+#ifndef prmc_h
+#define prmc_h
+
+#include "mpmtypes.h"
+
+
+extern Bool MutatorContextCanStepInstruction(MutatorContext context);
+extern Res MutatorContextStepInstruction(MutatorContext context);
+extern Addr MutatorContextSP(MutatorContext context);
+extern Res MutatorContextScan(ScanState ss, MutatorContext context,
+                              mps_area_scan_t scan, void *closure);
+
+
+#endif /* prmc_h */
+
+
+/* C. COPYRIGHT AND LICENSE
+ *
+ * Copyright (C) 2016 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * All rights reserved.  This is an open source license.  Contact
+ * Ravenbrook for commercial licensing options.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 
+ * 3. Redistributions in any form must be accompanied by information on how
+ * to obtain complete source code for this software and any accompanying
+ * software that uses this software.  The source code must either be
+ * included in the distribution or be available for no more than the cost
+ * of distribution plus a nominal fee, and must be freely redistributable
+ * under reasonable conditions.  For an executable file, complete source
+ * code means the source code for all modules it contains. It does not
+ * include source code for modules or files that typically accompany the
+ * major components of the operating system on which the executable file
+ * runs.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+ * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
diff --git a/mps/code/prmcan.c b/mps/code/prmcan.c
index bef53ad272e..7ff88abab40 100644
--- a/mps/code/prmcan.c
+++ b/mps/code/prmcan.c
@@ -1,4 +1,4 @@
-/* prmcan.c: PROTECTION MUTATOR CONTEXT (ANSI)
+/* prmcan.c: MUTATOR CONTEXT (ANSI)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
@@ -7,9 +7,9 @@
  * which is implemented in this module including the contracts for the
  * functions.
  *
- * .purpose: This module implements the part of the protection module
- * that implements the MutatorContext type.  In this ANSI version
- * none of the functions have a useful implementation.
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
+ * In this ANSI version none of the functions have a useful
+ * implementation.
  */
 
 #include "mpm.h"
@@ -17,9 +17,7 @@
 SRCID(prmcan, "$Id$");
 
 
-/* ProtCanStepInstruction -- can the current instruction be single-stepped */
-
-Bool ProtCanStepInstruction(MutatorContext context)
+Bool MutatorContextCanStepInstruction(MutatorContext context)
 {
   UNUSED(context);
 
@@ -27,9 +25,7 @@ Bool ProtCanStepInstruction(MutatorContext context)
 }
 
 
-/* ProtStepInstruction -- step over instruction by modifying context */
-
-Res ProtStepInstruction(MutatorContext context)
+Res MutatorContextStepInstruction(MutatorContext context)
 {
   UNUSED(context);
 
diff --git a/mps/code/prmcfri3.c b/mps/code/prmcfri3.c
index 73aeb4527b6..aeda5f8015f 100644
--- a/mps/code/prmcfri3.c
+++ b/mps/code/prmcfri3.c
@@ -1,10 +1,9 @@
-/* prmcfri3.c: PROTECTION MUTATOR CONTEXT INTEL 386 (FREEBSD)
+/* prmcfri3.c: MUTATOR CONTEXT INTEL 386 (FREEBSD)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
diff --git a/mps/code/prmcfri6.c b/mps/code/prmcfri6.c
index 6dee3c232b9..1631c9366af 100644
--- a/mps/code/prmcfri6.c
+++ b/mps/code/prmcfri6.c
@@ -1,10 +1,9 @@
-/* prmcfri6.c: PROTECTION MUTATOR CONTEXT x64 (FREEBSD)
+/* prmcfri6.c: MUTATOR CONTEXT x64 (FREEBSD)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext.
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * ASSUMPTIONS
diff --git a/mps/code/prmci3.c b/mps/code/prmci3.c
index d82e10f9fb9..26a6b139516 100644
--- a/mps/code/prmci3.c
+++ b/mps/code/prmci3.c
@@ -1,14 +1,13 @@
-/* prmci3.c: PROTECTION MUTATOR CONTEXT (INTEL 386)
+/* prmci3.c: MUTATOR CONTEXT (INTEL 386)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .design: See <design/prot/> for the generic design of the interface
+ * .design: See <design/prmc/> for the generic design of the interface
  * which is implemented in this module, including the contracts for the
  * functions.
  *
- * .purpose: This module implements the part of the protection module
- * that implements the MutatorContext type. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  * .requirements: Current requirements are for limited support only, for
  * stepping the sorts of instructions that the Dylan compiler might
@@ -31,9 +30,9 @@
  *
  * ASSUMPTIONS
  *
- * .assume.null: It's always safe for Prot*StepInstruction to return
- * ResUNIMPL.  A null implementation of this module would be overly
- * conservative but otherwise correct.
+ * .assume.null: It's always safe for MutatorContextCanStepInstruction
+ * to return FALSE. A null implementation of this module would be
+ * overly conservative but otherwise correct.
  *
  * .assume.want: The Dylan implementation is likely to access a
  * weak table vector using either MOV r/m32,r32 or MOV r32,r/m32
@@ -211,7 +210,7 @@ static Bool IsSimpleMov(Size *inslenReturn,
 }
 
 
-Bool ProtCanStepInstruction(MutatorContext context)
+Bool MutatorContextCanStepInstruction(MutatorContext context)
 {
   Size inslen;
   MRef src;
@@ -227,7 +226,7 @@ Bool ProtCanStepInstruction(MutatorContext context)
 }
 
 
-Res ProtStepInstruction(MutatorContext context)
+Res MutatorContextStepInstruction(MutatorContext context)
 {
   Size inslen;
   MRef src;
diff --git a/mps/code/prmci3.h b/mps/code/prmci3.h
index 78d5826374e..23f36303a0f 100644
--- a/mps/code/prmci3.h
+++ b/mps/code/prmci3.h
@@ -1,4 +1,4 @@
-/* prmci3.h: PROTECTION MUTATOR CONTEXT (Intel 386)
+/* prmci3.h: MUTATOR CONTEXT (Intel 386)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
diff --git a/mps/code/prmci6.c b/mps/code/prmci6.c
index 115e05c576a..7b98b44fc47 100644
--- a/mps/code/prmci6.c
+++ b/mps/code/prmci6.c
@@ -1,14 +1,13 @@
-/* prmci6.c: PROTECTION MUTATOR CONTEXT (x64)
+/* prmci6.c: MUTATOR CONTEXT (x64)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .design: See <design/prot/> for the generic design of the interface
+ * .design: See <design/prmc/> for the generic design of the interface
  * which is implemented in this module, including the contracts for the
  * functions.
  *
- * .purpose: This module implements the part of the protection module
- * that implements the MutatorContext type. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
@@ -20,9 +19,9 @@
  *
  * ASSUMPTIONS
  *
- * .assume.null: It's always safe for Prot*StepInstruction to return
- * ResUNIMPL.  A null implementation of this module would be overly
- * conservative but otherwise correct.
+ * .assume.null: It's always safe for MutatorContextCanStepInstruction
+ * to return FALSE. A null implementation of this module would be
+ * overly conservative but otherwise correct.
  *
  */
 
@@ -54,7 +53,7 @@ static Bool IsSimpleMov(Size *inslenReturn,
 }
 
 
-Bool ProtCanStepInstruction(MutatorContext context)
+Bool MutatorContextCanStepInstruction(MutatorContext context)
 {
   Size inslen;
   MRef src;
@@ -69,7 +68,7 @@ Bool ProtCanStepInstruction(MutatorContext context)
 }
 
 
-Res ProtStepInstruction(MutatorContext context)
+Res MutatorContextStepInstruction(MutatorContext context)
 {
   Size inslen;
   MRef src;
diff --git a/mps/code/prmci6.h b/mps/code/prmci6.h
index a33395f182d..516661592d2 100644
--- a/mps/code/prmci6.h
+++ b/mps/code/prmci6.h
@@ -1,4 +1,4 @@
-/* prmci6.h: PROTECTION MUTATOR CONTEXT (x64)
+/* prmci6.h: MUTATOR CONTEXT (x64)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
diff --git a/mps/code/prmcix.h b/mps/code/prmcix.h
index 00975f17fd1..0ac22e2e5d4 100644
--- a/mps/code/prmcix.h
+++ b/mps/code/prmcix.h
@@ -1,4 +1,4 @@
-/* prmcix.h:  PROTECTION MUTATOR CONTEXT (UNIX)
+/* prmcix.h:  MUTATOR CONTEXT (UNIX)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
diff --git a/mps/code/prmclii3.c b/mps/code/prmclii3.c
index 5ad655e53ce..c47d4fee0f0 100644
--- a/mps/code/prmclii3.c
+++ b/mps/code/prmclii3.c
@@ -1,10 +1,9 @@
-/* prmclii3.c: PROTECTION MUTATOR CONTEXT INTEL 386 (LINUX)
+/* prmclii3.c: MUTATOR CONTEXT INTEL 386 (LINUX)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
diff --git a/mps/code/prmclii6.c b/mps/code/prmclii6.c
index 0d98a135220..be2cfe0e3be 100644
--- a/mps/code/prmclii6.c
+++ b/mps/code/prmclii6.c
@@ -1,10 +1,9 @@
-/* prmclii6.c: PROTECTION MUTATOR CONTEXT x64 (LINUX)
+/* prmclii6.c: MUTATOR CONTEXT x64 (LINUX)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
diff --git a/mps/code/prmcw3i3.c b/mps/code/prmcw3i3.c
index 16b0047f23b..1a53ae4139d 100644
--- a/mps/code/prmcw3i3.c
+++ b/mps/code/prmcw3i3.c
@@ -1,12 +1,11 @@
-/* prmcw3i3.c: PROTECTION MUTATOR CONTEXT INTEL 386 (Windows)
+/* prmcw3i3.c: MUTATOR CONTEXT INTEL 386 (Windows)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
  * PURPOSE
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  * SOURCES
  *
diff --git a/mps/code/prmcw3i6.c b/mps/code/prmcw3i6.c
index 493e4f19a3a..18f1e728454 100644
--- a/mps/code/prmcw3i6.c
+++ b/mps/code/prmcw3i6.c
@@ -1,12 +1,11 @@
-/* prmcw3i6.c: PROTECTION MUTATOR CONTEXT INTEL x64 (Windows)
+/* prmcw3i6.c: MUTATOR CONTEXT INTEL x64 (Windows)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
  * PURPOSE
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  * SOURCES
  *
diff --git a/mps/code/prmcxc.h b/mps/code/prmcxc.h
index 4818749c42f..af145a6e603 100644
--- a/mps/code/prmcxc.h
+++ b/mps/code/prmcxc.h
@@ -1,4 +1,4 @@
-/* prmcxc.h: PROTECTION MUTATOR CONTEXT FOR OS X MACH
+/* prmcxc.h: MUTATOR CONTEXT FOR OS X MACH
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
diff --git a/mps/code/prmcxci3.c b/mps/code/prmcxci3.c
index 93729ac8fc6..03fe3d836f0 100644
--- a/mps/code/prmcxci3.c
+++ b/mps/code/prmcxci3.c
@@ -1,10 +1,9 @@
-/* prmcxci3.c: PROTECTION MUTATOR CONTEXT INTEL 386 (MAC OS X)
+/* prmcxci3.c: MUTATOR CONTEXT INTEL 386 (MAC OS X)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
diff --git a/mps/code/prmcxci6.c b/mps/code/prmcxci6.c
index e27b13d77a7..269deb4b275 100644
--- a/mps/code/prmcxci6.c
+++ b/mps/code/prmcxci6.c
@@ -1,10 +1,9 @@
-/* prmcxci6.c: PROTECTION MUTATOR CONTEXT x64 (OS X)
+/* prmcxci6.c: MUTATOR CONTEXT x64 (OS X)
  *
  * $Id$
  * Copyright (c) 2001-2016 Ravenbrook Limited.  See end of file for license.
  *
- * .purpose: This module implements the part of the protection module
- * that decodes the MutatorContext. 
+ * .purpose: Implement the mutator context module. See <design/prmc/>.
  *
  *
  * SOURCES
diff --git a/mps/code/prot.h b/mps/code/prot.h
index 2664ae48b92..4a6f6a23aa2 100644
--- a/mps/code/prot.h
+++ b/mps/code/prot.h
@@ -25,15 +25,6 @@ extern void ProtSet(Addr base, Addr limit, AccessSet mode);
 extern void ProtSync(Arena arena);
 
 
-/* Mutator Fault Context */
-
-extern Bool ProtCanStepInstruction(MutatorContext context);
-extern Res ProtStepInstruction(MutatorContext context);
-extern Addr MutatorContextSP(MutatorContext context);
-extern Res MutatorContextScan(ScanState ss, MutatorContext context,
-                              mps_area_scan_t scan, void *closure);
-
-
 #endif /* prot_h */
 
 
diff --git a/mps/code/pthrdext.c b/mps/code/pthrdext.c
index 8b1c3c9ebcf..1d4851878e3 100644
--- a/mps/code/pthrdext.c
+++ b/mps/code/pthrdext.c
@@ -55,8 +55,6 @@ static RingStruct suspendedRing;            /* PThreadext suspend ring */
  *
  * See <design/pthreadext/#impl.suspend-handler>
  *
- * The interface for determining the MFC might be platform specific.
- *
  * Handle PTHREADEXT_SIGSUSPEND in the target thread, to suspend it until
  * receiving PTHREADEXT_SIGRESUME (resume). Note that this is run with both
  * PTHREADEXT_SIGSUSPEND and PTHREADEXT_SIGRESUME blocked. Having
diff --git a/mps/code/thix.c b/mps/code/thix.c
index 8d03779c024..a5207f0f8db 100644
--- a/mps/code/thix.c
+++ b/mps/code/thix.c
@@ -276,7 +276,7 @@ Res ThreadScan(ScanState ss, Thread thread, Word *stackCold,
     if(res != ResOK)
       return res;
 
-    /* scan the registers in the mutator fault context */
+    /* scan the registers in the mutator context */
     res = MutatorContextScan(ss, context, scan_area, closure);
     if(res != ResOK)
       return res;
diff --git a/mps/code/thxc.c b/mps/code/thxc.c
index 7d4ce2bcb1d..bcac8296b50 100644
--- a/mps/code/thxc.c
+++ b/mps/code/thxc.c
@@ -263,7 +263,7 @@ Res ThreadScan(ScanState ss, Thread thread, Word *stackCold,
     if(res != ResOK)
       return res;
 
-    /* scan the registers in the mutator fault context */
+    /* scan the registers in the mutator context */
     res = MutatorContextScan(ss, &context, scan_area, closure);
     if(res != ResOK)
       return res;
diff --git a/mps/design/an.txt b/mps/design/an.txt
index 78ecccfeafb..a6cbdf6d364 100644
--- a/mps/design/an.txt
+++ b/mps/design/an.txt
@@ -100,7 +100,7 @@ _`.mod`: This section lists the functional modules in the MPS.
 
 _`.mod.lock`: Locks. See design.mps.lock_.
 
-_`.mod.prmc`: Protection mutator context. See design.mps.prmc_.
+_`.mod.prmc`: Mutator context. See design.mps.prmc_.
 
 _`.mod.prot`: Memory protection. See design.mps.prot_.
 
@@ -136,7 +136,7 @@ design.mps.prmc.impl.an.fault_) and requires a single-threaded mutator
 
 _`.lim.prot`: Does not support incremental collection (see
 design.mps.prot.impl.an.sync_) and is not compatible with
-implementations of the protection mutator context module that support
+implementations of the mutator context module that support
 single-stepping of accesses (see design.mps.prot.impl.an.sync.issue_).
 
 _`.lim.sp`: Only suitable for use with programs that do not handle
@@ -176,7 +176,7 @@ Document History
 Copyright and License
 ---------------------
 
-Copyright © 2014 Ravenbrook Limited <http://www.ravenbrook.com/>.
+Copyright © 2014-2016 Ravenbrook Limited <http://www.ravenbrook.com/>.
 All rights reserved. This is an open source license. Contact
 Ravenbrook for commercial licensing options.
 
diff --git a/mps/design/exec-env.txt b/mps/design/exec-env.txt
index 71d7287f057..4dac219a8cb 100644
--- a/mps/design/exec-env.txt
+++ b/mps/design/exec-env.txt
@@ -112,10 +112,10 @@ The core must be freestanding.
 
 _`.arch.platform`: The *platform* provides the core with interfaces to
 features of the operating system and processor (locks, memory
-protection, protection mutator context, stack probing, stack and
-register scanning, thread management, and virtual memory). The
-platform is specialized to a particular environment and so can safely
-use whatever features are available in that environment.
+protection, mutator context, stack probing, stack and register
+scanning, thread management, and virtual memory). The platform is
+specialized to a particular environment and so can safely use whatever
+features are available in that environment.
 
 _`.arch.plinth`: The *plinth* provides the core with interfaces to
 features of the user environment (time, assertions, and logging). See
diff --git a/mps/design/index.txt b/mps/design/index.txt
index decfb0fe66d..66530dc7a63 100644
--- a/mps/design/index.txt
+++ b/mps/design/index.txt
@@ -85,7 +85,7 @@ poolmrg_                Manual Rank Guardian pool class
 poolmv_                 Manual Variable pool class
 poolmvt_                Manual Variable Temporal pool class
 poolmvff_               Manual Variable First-Fit pool class
-prmc_                   Protection mutator context
+prmc_                   Mutator context
 prot_                   Memory protection
 protli_                 Linux implementation of protection module
 protocol_               Protocol inheritance
diff --git a/mps/design/prmc.txt b/mps/design/prmc.txt
index 34632964369..d16bd3faaa5 100644
--- a/mps/design/prmc.txt
+++ b/mps/design/prmc.txt
@@ -1,7 +1,7 @@
 .. mode: -*- rst -*-
 
-Protection mutator context
-==========================
+Mutator context
+===============
 
 :Tag: design.mps.prmc
 :Author: Gareth Rees
@@ -9,31 +9,30 @@ Protection mutator context
 :Status: complete design
 :Revision: $Id$
 :Copyright: See `Copyright and License`_.
-:Index terms: pair: protection mutator context; design
+:Index terms: pair: mutator context; design
 
 
 Introduction
 ------------
 
-_`.intro`: This is the design of the protection mutator context
-module.
+_`.intro`: This is the design of the mutator context module.
 
 _`.readership`: Any MPS developer; anyone porting the MPS to a new
 platform.
 
-_`.overview`: The protection mutator context module decodes the
-*context* of a mutator thread at the point when it caused a protection
-fault, so that access to a protected region of memory can be handled,
-or when it was suspended by the thread manager, so that its registers
-and control stack can be scanned.
+_`.overview`: The mutator context module decodes the *context* of a
+mutator thread at the point when it caused a protection fault, so that
+access to a protected region of memory can be handled, or when it was
+suspended by the thread manager, so that its registers and control
+stack can be scanned.
 
 _`.def.context`: The *context* of a thread (also called its
 *continuation*) is an abstract representation of the control state of
 the thread at a point in time, including enough information to
 continue the thread from that point.
 
-_`.status`: The protection mutator context module does not currently
-present a clean interface to the rest of the MPS: source files are
+_`.status`: The mutator context module does not currently present a
+clean interface to the rest of the MPS: source files are
 inconsistently named, and the implementation is (necessarily) mixed up
 with the implementation of the memory protection module
 (design.mps.prot_) and the thread manager
@@ -64,7 +63,7 @@ weak hash tables. See request.dylan.160044_.)
 
 .. _request.dylan.160044: https://info.ravenbrook.com/project/mps/import/2001-11-05/mmprevol/request/dylan/160044/
 
-_`.req.suspend.scan`: Must capature enough information to ambiguously
+_`.req.suspend.scan`: Must capture enough information to ambiguously
 scan all roots in the context of a thread that has been suspended by
 the thread manager. (This is necessary for conservative garbage
 collection to work. See design.mps.thread-manager.if.scan_.)
@@ -85,14 +84,14 @@ See design.mps.thread-manager.if.thread_.
 
 .. _design.mps.thread-manager.if.thread: thread-manager#if.thread
 
-``Bool ProtCanStepInstruction(MutatorContext context)``
+``Bool MutatorContextCanStepInstruction(MutatorContext context)``
 
 _`.if.canstep`: Examine the context to determine whether the
 protection module can single-step the instruction which is causing the
-fault. Return ``TRUE`` if ``ProtStepInstruction()`` is capable of
-single-stepping the instruction, or ``FALSE`` if not.
+fault. Return ``TRUE`` if ``MutatorContextStepInstruction()`` is
+capable of single-stepping the instruction, or ``FALSE`` if not.
 
-``Bool Res ProtStepInstruction(MutatorContext context)``
+``Bool Res MutatorContextStepInstruction(MutatorContext context)``
 
 _`.if.step`: Single-step the instruction which is causing the fault.
 Update the mutator context according to the emulation or execution of
@@ -101,8 +100,8 @@ instruction which was caused the fault to be re-executed. Return
 ``ResOK`` if the instruction was single-stepped successfully, or
 ``ResUNIMPL`` if the instruction cannot be single-stepped.
 
-This function is only called if ``ProtCanStepInstruction(context)``
-returned ``TRUE``.
+This function is only called if
+``MutatorContextCanStepInstruction(context)`` returned ``TRUE``.
 
 ``Res MutatorContextScan(ScanState ss, MutatorContext context, mps_area_scan_t scan, void *closure)``
 
diff --git a/mps/design/prot.txt b/mps/design/prot.txt
index a3ff8e35a38..2190eb1c3c4 100644
--- a/mps/design/prot.txt
+++ b/mps/design/prot.txt
@@ -153,8 +153,8 @@ Document History
 
 - 2013-05-23 GDR_ Converted to reStructuredText.
 
-- 2014-10-23 GDR_ Move protection mutator context interface to
-  design.mps.prmc_. Bring design up to date.
+- 2014-10-23 GDR_ Move mutator context interface to design.mps.prmc_.
+  Bring design up to date.
 
   .. _design.mps.prmc: prmc
 
diff --git a/mps/manual/source/code-index.rst b/mps/manual/source/code-index.rst
index 7e85c4c0237..a14aabeb59e 100644
--- a/mps/manual/source/code-index.rst
+++ b/mps/manual/source/code-index.rst
@@ -163,6 +163,7 @@ lock.h        Lock interface. See design.mps.lock_.
 lockan.c      Lock implementation for standard C.
 lockix.c      Lock implementation for POSIX.
 lockw3.c      Lock implementation for Windows.
+prmc.h        Mutator context interface. See design.mps.prmc_.
 prmcan.c      Mutator context implementation for standard C.
 prmcfri3.c    Mutator context implementation for FreeBSD, IA-32.
 prmcfri6.c    Mutator context implementation for FreeBSD, x86-64.
diff --git a/mps/manual/source/topic/porting.rst b/mps/manual/source/topic/porting.rst
index c61d710374d..bfe3c1adef3 100644
--- a/mps/manual/source/topic/porting.rst
+++ b/mps/manual/source/topic/porting.rst
@@ -69,13 +69,13 @@ usable.
    there is no further need to protect it. This means it can't support
    incremental collection, and has no control over pause times.
 
-#. The **protection mutator context** module figures out what the
-   :term:`mutator` was doing when it caused a :term:`protection
-   fault`, so that access to a protected region of memory can be
-   handled, or when a thread was suspended, so that its
-   :term:`registers` and :term:`control stack` can be scanned.
+#. The **mutator context** module figures out what the :term:`mutator`
+   was doing when it caused a :term:`protection fault`, so that access
+   to a protected region of memory can be handled, or when a thread
+   was suspended, so that its :term:`registers` and :term:`control
+   stack` can be scanned.
 
-   See :ref:`design-prmc` for the design, and ``prot.h`` for the
+   See :ref:`design-prmc` for the design, and ``prmc.h`` for the
    interface. There are implementations on Unix, Windows, and OS X for
    IA-32 and x86-64.