Open Implementation (OI) + Adaptive Programming (AP)
= Adaptive Open Implementation
----------------------------------------------------

The Demeter project 
(http://www.ccs.neu.edu/research/demeter)
at the Adaptive Software Laboratory
at Northeastern University works 
on a technique which
helps to open implementations 
in a useful way. 

An adaptive program is a program 
written in an OI style as follows:
It is a behaviors family (primary program)
which is customized by a
meta-level object. Each primary behaviors family
refers to partial information
in the meta-level object.  The 
partial information allows us to flexibly
write the application program we 
want, yet we can make many
changes to the meta-level customizer
without having to update the primary
program, leading to adaptiveness.
One specific kind of adaptive 
programs are programs which are written
in terms of succinct traversal 
specifications and the meta-level
customizers are class graphs.
The  succinct traversal specifications 
reveal the important
parts of the implementation structure 
which needs to exist
in any use of the program.
The implementation is opened for the purpose
of using the program in a wide range of new,
even unexpected, contexts.


 
AP from an OI point of view:
The architecture of AOI

-------------------------------------------
primary       	meta		meta-meta

b_p 		b_m				behaviors family
o_p		o_m				objects family
		o_m includes
		  s_p		s_m		structure

i_p 		i_m		i_m_m
-------------------------------------------

Legend:
b: behaviors family
o: objects family
s: structure
i: interface

_p: primary
_m: meta

Differences between OI and Adaptive OI (AOI):

With AOI, oppenness is built in. Each primary behaviors family 
proclaims an ``invariant'' and the program can 
adjust aspects of the program provided the invariant holds.

In AOI we only use partial information about structural meta objects
while in ordinary OI the details of the structural meta objects
is encoded into the primary program.

In AOI, primary is incomplete without meta and meta-meta.
meta is incomplete without meta-meta.
Reason: each primary behaviors family refers to relevant, but
  partial information in meta.

In AOI, there is a need for a concept called adaptive introspection.
It is a form of intercession, but once the meta-object customizer
has been updated and remains constant, we have introspection only.

==================================

Example (for Demeter users)

Prefix expression evaluator
-------------------------------------------
primary       	meta		meta-meta

eval.pp		g_print.pp
exp		exp.cd
				dem.cd
-------------------------------------------

Legend:
eval.pp		evaluator
exp		prefix expression
g_print.pp	printing of objects
exp.cd		class dictionary for prefix expressions
		  (the only meta object)
dem.cd		Demeter's heart