Roger --

You may be interested in the one-day symposium on Versioning, to be 
held the day the before Balisage: The Markup Conference.

For information on the Versioning preconference see:
    http://www.balisage.net/Versioning/index.html
For information on Balisage, see: http://www.balisage.net/

I expect participants to address the issues you have identified here, 
among others.

-- Tommie


At 3:55 PM -0500 12/7/07, Costello, Roger L. wrote:
>Hi Folks,
>
>Oftentimes when discussing a "versioning strategy" I focus on how to
>design schemas in a fashion to lessen the impact of changes.  It occurs
>to me that this addresses only one aspect of the data versioning
>problem.  Below I have attempted to identify other issues to be
>addressed in a data versioning strategy.  I am interested in hearing
>your thoughts on this.
>
>EVOLVING DATA
>
>Suppose some data is regularly exchanged between machines:
>
>Machine 1 --> data --> Machine 2
>Machine 1 <-- data <-- Machine 2
>
>Periodically the data changes due to requirement changes, additional
>insights, or from innovation.
>
>A change results in a new "version" of the data.
>
>
>PROBLEM
>
>What are the categories of changes that may occur?  What categories of
>changes must be dealt with by a data versioning strategy?
>
>
>CATEGORIES OF CHANGE
>
>1. Semantic - the meaning of the data changes.
>
>Example:
>
>version 1 data: a "distance" value means the distance from the center
>of town.
>
>version 2 data: a distance value means the distance from the town line.
>
>2. Relationship - the relationship between the data changes.
>
>Example:
>
>version 1 data: there is a co-constraint between the start-time and the
>end-time. 
>         
>version 2 data: there is a three-way co-constraint between start-time,
>end-time, and mode-of-transportation.
>
>3. Syntax - the structure of the data changes.
>
>Example:
>
>version 1 data: the employee data is listed first and the person's name
>is given by his given-name and surname.
>         
>version 2 data: the department data is listed first and in the employee
>data each person's name additionally contains a middle name.
>
>
>SUPPORTING TECHNOLOGIES
>
>Suppose the data being exchanged is formatted using the XML syntax. 
>
>Machine 1 --> XML --> Machine 2
>Machine 1 <-- XML <-- Machine 2
>
>What technologies support the above categories of change?
>
>1. Semantic: A data dictionary may be used to define meaning.
>
>2. Relationship: Schematron may be used to express relationships
>between data.
>
>3. Syntax: XML Schema, Relax NG, or DTD may be used to express the
>structure of the data.
>
>
>REQUIREMENTS ON A VERSIONING STRATEGY
>
>A versioning strategy must take into consideration:
>
>- changes in the semantics of the data
>- changes in the relationships of the data
>- changes in the syntax of the data
>
>When data is in an XML format then a versioning strategy must
>implement:
>
>- versioning a data dictionary
>- versioning a Schematron schema
>- versioning an XML Schema, Relax NG schema, or DTD
>
>
>QUESTIONS
>
>a. Do you agree with the three categories of change? 
>
>b. Do these categories represent all types of change?
>
>c. Do you agree that a versioning strategy must address semantic,
>relationship, and syntactic changes?
>
>/Roger
>
>
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-- 

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B. Tommie Usdin                        mailto:btusdin@m...
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