I wish to thank for numerous answers to my call for help.
Due to their number and a certain similarity, I post here
a common response.
My friend, the general, stays faithful to some rules he learned
from me. One of them says that
1.A computer system usually represents reality, through the potential
E(ntity)/R(elation) DB schema, instantiated dynamically by programmed
procedures, and
2.First design step consists in defining the logical ER structure.
It is discouraged to consider any implementation steps before
having fixed the ER structure in simplest form of symbols and
arrows. Thinking for instance SQL before having fixed the ER,
often, if not always, screws up the latter. Whatever the reality
may be, it does not consist of tables entangled with foreign keys.
In the Air Force they have top software engineers and programmers
capable to implement much more efficient application details than
myself. But my former student still believes in my reality modeling
flair, thinks that most efficient application reposing on a wrong
ER is necessarily a failure and wishes to see if and to what extent
my old ER vision applies to the modern context. Now, being naturally
biased towards my old design, I asked for impartial ideas.
The problem consists in showing a concrete ER structure best
supporting
1.Exploding a plane via recursive aggregate/part relation into all
parts,
2.Imploding a part via part/aggregate relation into all planes.
As byproduct, indicating disassemble paths for a part, with
quantities at each aggregate.
By "best" I mean entirely flexible, i.e. open to all sorts of
insertions, deletions and modifications by programs, without
impacting the DB schema.
The ER structure is most simply shown with symbols and arrows.
For instance, one to many relation father/child and many to many
relation student/course may be shown as:
fthr ---> chld
stdnt <---> crs
Thanks for your assistance and looking forward to further help.
Georges.
--
You received this message because you are subscribed to the Google Groups
"Epistemology" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/epistemology?hl=en.
