FW: Creation of Image.

agree at carltonfields.com agree at carltonfields.com
Wed Jan 20 18:09:25 UTC 1999


I'm quite sure I don't understand the nuances of this discussion, but I'll 
venture the following: In what significant manner is an initial image, and 
workspace script not a concise and effective specification of the new image.  
(Remember that SystemTracer permits the specification of Sets of classes to be 
included/excluded from the new image, and also provides methods to "clean up" 
an existing image).

Given that most practical applications can be reduced to the desired content 
via a change set (including all the declarative code to "set up" the classes), 
why, is it necessary to have a complete declarative specification from the 
"ground up" of the build of the entire underlying system in practice?  I have 
made builds of significant commercial applications and given arms-length 
entities source code "deliverables" and a makefile for constructing them, 
together with appropriate documentation.  On the other hand, I have never 
provided or considered providing source codes of the compiler libraries, 
together with code and makefiles for the same (and often didn't have them), 
except to the extent they were modified in order to produce the application.  
[As a practical matter, I do typically deliver them in object code at least to 
assure they can perform a rebuild in the future.]  Nor did I routinely specify 
the underlying system facilities (compiler, linker, system rom and OS code) 
upon which the application relies for build and execution, other than to 
identify the name and version when relevant.

Have I failed to provide my clients with an adequate specification of the 
application, as the term is used below?  (Perhaps I was right to have changed 
professions, after all :-) )  In what sense is it meaningful or important to 
have so detailed a specification?

I wrote because it seemed to me that this discussion was going around in 
circles:  

	The suggestion was made that a scratch rebuild facility without use of an 
existing image was desired.

	In response, It was suggested that the SystemTracer would suit most needs for 
a scratch rebuild facility.  

	In rebuttal, it was suggested that the SystemTracer is inadequate, for it 
doesn't produce a specification sufficient for the system to be built from 
scratch without an existing image.

As understood, the last point seems to beg the question.  As I noted earlier, 
I am fairly certain I am missing the point, and write here in the selfish hope 
that expressing my confusion will lead someone to straighten me out and 
clarify for me the issues.

-----Original Message-----
From:	MIME :sarkela at home.com 
Sent:	Wednesday, January 20, 1999 4:39 AM
To:	squeak at cs.uiuc.edu
Subject:	Re: Creation of Image.

I suspect that Dwight sees the same difference I see between the
specification of a thing and the thing itself. The SystemTracer uses
the actual objects as the core of the specification of the new image
to be written. A declarative specification of an image would be
comprised of class, method, pool, pool variable, global variable,
instance variable, class variable definitions as well as the initializers
required to bring those variables to a state in which Smalltalk program
execution may occur.





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