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000123_gadia@cs.iastate.edu _Thu May 13 19:10:52 1993.msg
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Message-Id: <199305140010.AA23347@optima.cs.arizona.edu>
Received: from ren.cs.iastate.edu by optima.cs.arizona.edu (5.65c/15) via SMTP
id AA23347; Thu, 13 May 1993 17:10:52 MST
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From: Shashi K. Gadia <gadia@cs.iastate.edu>
Subject: Benchmark database instance
To: tsql@cs.arizona.edu
Date: Thu, 13 May 93 19:10:52 CDT
Cc: gadia@cs.iastate.edu
Mailer: Elm [revision: 70.30]
I have four points to make about
the database instance.
1. Change in Ed (Edwards's) information.
-----------------------------------------
Ed's name changes at a time instant
at which he possesses all three skills.
In most models this will make the description
of his skills unnecessarily lengthy. I
suggest two changes.
A. Let the new name (Edward) start at
1/1/89 instead of 1/1/88.
B. Change end time of typing skill to
12/31/87.
With these changes, his name changes only
during the filing skill.
2. The Department <--> Manager dependency.
------------------------------------------
The proposed instance fails to reflect
the complexity of the database scheme.
The situation in general can be much more
interesting than the one exhibited while
still satisfying the two dependencies
(Department --> Manager, and Manager
--> Department). The implication of these
dependencies is that Department
can serve as a key, and if one wishes,
Manager can serve as the key. Objects
viewed with respect to these different
keys are interwoven. In addition,
even the number of tuples can be
different with respect to different
keys. This is one of the interesting
peculiarities of temporal (and parametric)
databases which the community must
address.
3. Relation with a non-interval domain.
---------------------------------------
There is no relation whose domain
is a non-interval temporal element.
4. Representation of time points.
---------------------------------
The time points are dates in the format
MM/DD/YY. This is extremely distracting
and serves no purpose whatsoever.
Dates form a sequence 1/1/82, 1/2/82, ...
etc. So do integers 0, 1, 2, ...
The two structures are literally
isomorphic in our context. There are many
reasons that dates are not desirable.
A. An interval requires 19 characters.
To draw an instance of emp relation I need
101 characters and spaces. This is very
taxing in terms of document preparation.
B. For a human it is much harder to compare
dates than integers. This becomes very taxing
when we try to visualize what is retrieved
by a query.
I feel very strongly about these issues
which makes the benchmark document inaccessible
and less appealing.
I will be willing to provide an instance
which takes these points into full
consideration.