--- a/unix-phil.ms	Wed Feb 24 18:05:54 2010 +0100
+++ b/unix-phil.ms	Thu Feb 25 15:06:34 2010 +0100
@@ -654,7 +654,7 @@
 
 
 .NH 1
-Case study: nmh
+Case study: \s-1MH\s0
 .LP
 The last chapter introduced and explained the Unix Philosophy
 from a general point of view.
@@ -665,25 +665,68 @@
 .PP
 This first case study is about the mail user agents \s-1MH\s0
 (``mail handler'') and its descendent \fInmh\fP (``new mail handler'').
+In this document, the name \s-1MH\s0 will be used for both of them.
+A distinction will only be made if differences between
+them are described.
 
 
 .NH 2
-History of \s-1MH\s0
+Historical background
 .LP
-In 1977, Stockton Gaines and Norman Shapiro of the \s-1RAND\s0 Corporation
-came up with a concept for a new electronic mail system.
-Till then, \s-1RAND\s0 had used \s-1MS\s0 (``mail system''),
-which was monolithic.
-In 1978 and 1989, Bruce Borden implemented the concept \(en
-this was the birth of \s-1MH\s0.
+Electronic mail was available in Unix very early.
+It is out of matter that in the beginning mail was only
+transferred within one machine.
+This chapter is about a mail user agent (\s-1MUA\s0),
+which provides functions to read, compose, and organize mail,
+but (ideally) not to transfer.
+.PP
+The first \s-1MUA\s0 on Unix was \f(CWmail\fP.
+It was a small program that either prints the own mailbox file
+or appends text to someone elses mailbox file,
+depending on the command line arguments.
+.[
+%O http://cm.bell-labs.com/cm/cs/who/dmr/pdfs/man12.pdf
+.]
+It was a program that did one job well.
+This job was emailing, which then was very simple.
+.PP
+Later, emailing became more powerfull, and thus more complex.
+The simple \f(CWmail\fP, which knew nothing of subjects,
+independent handling of single messages,
+and long-time storage of them, was not powerful enough anymore.
+At Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
+in 1978 to provide additional functions for emailing.
+Mail was still one program, but now it was large and did
+several jobs.
+Its user interface is modeled after the one of ed.
+It is designed for humans, but is still scriptable.
+\fImailx\fP is the adaption of Berkeley Mail into System V.
+.[
+%A Gunnar Ritter
+%O http://heirloom.sourceforge.net/mailx_history.html
+.]
+Elm, pine, mutt, and today a whole bunch of graphical \s-1MUA\s0s
+followed Mail's direction.
+They are large, monolithic programs which include all emailing functions.
+.PP
+A different way took the people of \s-1RAND\s0 Corporation.
+In the beginning, they also had used a monolitic mail system,
+simply called \s-1MS\s0 for ``mail system''.
+But in 1977, Stockton Gaines and Norman Shapiro
+came up with a proposal of a new email system concept \(en
+one that honors the Unix Philosophy.
+The concept was implemented by Bruce Borden in 1978 and 1979.
+This was the birth of \s-1MH\s0 \(en the ``mail handler''.
 .PP
 Since then, \s-1RAND\s0, the University of California at Irvine and
-at Berkeley, and several others have contributet to the software.
+at Berkeley, and several others have contributed to the software.
 However, it's core concepts remained the same.
-In the 90s, the development of \s-1MH\s0 slowed down.
-Richard Coleman started with \fInmh\fP, the new mail handler,
-in 1997 to improve \s-1MH\s0, especially in regard of modern emailing.
-Today, nmh is developed by various people on the internet.
+In the 90s, when development of \s-1MH\s0 slowed down,
+Richard Coleman started with \fInmh\fP, the new mail handler.
+This was in 1997.
+His goal was to improve \s-1MH\s0, especially in regard of 
+the requirements of modern email.
+Today, nmh is developed by various people on the Internet.
 .[
 %T RAND and the Information Evolution: A History in Essays and Vignettes
 %A Willis H. Ware 
@@ -702,15 +745,108 @@
 .]
 
 .NH 2
-Contrasts to similar sw
+Contrasts to similar software
 .LP
-vs. Thunderbird, mutt, mailx, pine
+All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
+This might not be completely true,
+but it reflects the general situation pretty well.
+.PP
+While monolithic \s-1MUA\s0s gather all function in one program,
+\s-1MH\s0 is a toolchest of many small tools \(en one for each job.
+Following is a list of important programs of \s-1MH\s0's toolchest:
+.IP \(bu
+.CW inc :
+incorporate new mail
+.IP \(bu
+.CW scan :
+list messages in folder
+.IP \(bu
+.CW show :
+show message
+.IP \(bu
+.CW next\fR/\fPprev :
+show next/previous message
+.IP \(bu
+.CW folder :
+change current folder
+.IP \(bu
+.CW refile :
+refile message into folder
+.IP \(bu
+.CW rmm :
+remove message
+.IP \(bu
+.CW comp : 
+compose a new message
+.IP \(bu
+.CW repl :
+reply to a message
+.IP \(bu
+.CW forw : 
+forward a message
+.IP \(bu
+.CW send : 
+send a prepared message
 .LP
-flexibility, no redundancy, use the shell
+\s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
+The user does not leave the shell to run \s-1MH\s0,
+but he uses \s-1MH\s0 within the shell.
+\s-1MH\s0's mail storage is (only little more than) a directory tree
+where directories are mail folders and files are mail messages.
+Working with \s-1MH\s0's toolchest is much like working
+with Unix' toolchest:
+\f(CWscan\fP is like \f(CWls\fP,
+\f(CWshow\fP is like \f(CWcat\fP,
+\f(CWfolder\fP is like \f(CWcd\fP,
+\f(CWrefile\fP is like \f(CWmv\fP,
+and \f(CWrmm\fP is like \f(CWrm\fP.
+.PP
+The most important difference to Unix' toolchest is,
+that \s-1MH\s0's tools have an own context.
+The context of the Unix tools is mainly the current working directory,
+the user identification, and the environment variables.
+\s-1MH\s0 extends this context by two more items:
+A current mail folder, similar to the current working directory,
+is maintained; \f(CWfolder\fP provides the functionality
+of \f(CWpwd\fP and \f(CWcd\fP for it.
+A current message, relative to the current folder, is maintained.
+This enables commands like \f(CWnext\fP and \f(CWprev\fP.
+In contrast to Unix' context, which is chained to the shell session,
+\s-1MH\s0's context is meant to be chained to a mail account.
+Actually, the current message is a property of the mail folder.
+This is without problem as long as a mail folder belongs to one user.
+But when multiple users want to work on one mail folder simultaneously,
+it will cause problems.
+This is a legacy from a time when emailing was different.
+.PP
+Using a monolithic program with a captive user interface
+means ``entering'' the program, using it, and ``leaving'' the program.
+Using a toolchest like \s-1MH\s0 means running programs,
+alone or in combinition with others, even from other toolchests,
+without leaving the shell.
 
 .NH 2
 Gains of the design
 .LP
+\s-1MH\s0 is perfectly suited for non-interactive use.
+It offers all functions directly and without captive user interfaces.
+If users want a graphical user interface, anyhow,
+they can have it with \fIxmh\fP or \fIexmh\fP.
+These are graphical frontends for the \s-1MH\s0 toolchest.
+This means, all email-related work is still done by \s-1MH\s0 tools,
+but xmh issues the calls when the user clicks a button.
+Providing easy-to-use user interfaces as frontends is a good
+approach, because it does not limit the power of the backend itself.
+The frontend will anyways only be able to make a part of the
+backend's power and flexibility available.
+If it is separate, then the missing parts can still be accessed
+at the backend directly.
+If it is integrated, then this will hardly be possible.
+.PP
+flexibility, no redundancy, use the shell
+
+.PP
+easy to write: see ksh-book
 
 .NH 2
 Problems