The ProductionRule pattern adds some power and reuse to  http://st-www.cs.uiuc.edu/cgi-bin/wikic/wikic?InterpreterPattern. [[InterpreterPattern?]]

''Doesn't seem to be any mention of ProductionRule there''

There are two main improvements.  First, it turns out that you
can create new production rules as
as objects (instead of as classes). This means that in five programming
statements you can define
a language that has five grammar rules.  Powerful!


The second
improvement is the use of application-specific Stackers instead
of visitors.
Stackers are helpers that get plugged into production rules.  When
you write a production rule, you can hand it a Stacker that does
whatever you want to have happen when the rule fires.  For example,
if you're parsing an HTML file, when you see some <BOLD> stuff, you
can have a stacker set the text style to be bold.

''Any relation to Assemblers and Assemblies?''

I've written this up in more detail in an article that I'm hoping will show
up in Java Report in a few months.  If you're aching to know more
and can't wait, drop me a note at Steve dot Metsker@acm dot org.

----
See also RewriteRules