[Year 12 IT Apps] Logical and physical data dictionaries

[Mark KELLY]

Hi all.  I've flipped and flopped over the years about whether I thought
data dictionaries were logical or physical design tools.  On one page on my
Lecture Notes I had them as logical, on another page they were physical. Now
I've a sneaking suspicion that *both* are right: there are logical data
dictionaries and physical data dictionaries...

To quote
http://www.modernanalyst.com/Careers/InterviewQuestions/tabid/128/articleType/ArticleView/articleId/1392/categoryId/45/What-is-a-logical-data-dictionary-and-what-are-the-benefits-of-maintaining-one.aspx

*"At a logical level, the business representative cares about questions such
as:

What is a Sales Contract?
What are the primary elements of a Sales Contract?
Do these primary elements have attributes or data of their own?
How does a Sales Contract relate to other relevant business entities?

Once data has been logically defined, the definition and relationships
between various pieces of logical data rarely need to change.
In contrast, a physical data dictionary allows an organization to describe
data in terms of its physical data structure, type, format, and length.
Physical data dictionaries provide programmers of many different systems
with a tool to understand how and where the data is stored and how it must
be referenced in order to consume it."*

Has anyone else discovered these 2 varieties of data dictionaries?

--
Mark Kelly
Manager Information Systems
Reporting Manager
IT Learning Area Manager

McKinnon Secondary College
McKinnon Rd McKinnon 3204
Victoria, Australia
Direct line / Voicemail: +613 8520 9085
Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au

VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist

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