Re: Logically model never possible real world or my forever imperfect business?

From: Alan <>
Date: Fri, 7 Mar 2003 09:12:46 -0500
Message-ID: <b4a9cq$1tvpis$>

If you can't re-engineer the current process, then you have to model what exists now.

"OlegJay" <> wrote in message
> Please help me understand the proper 3rd Normal Form for the following
> simple Model.
> If your new project has to live with old inefficient business rules do
> you logically model
> (up to third normal form) the business with its limits it will always
> live with or
> do you data model an ideal world/business that it will never come
> close to?
> When I get to the physical design and more complexities (such as
> resolving many to many
> and including maintaining history) I'm sure I'll make chooses if
> needed that will
> keep the design to the reality of my business rather than some
> standardized ideal world.
> Just take as an example the real estate transactions recording
> business where "we use type
> written documents as your input and have data entry people pick out
> transaction
> info. and the system later accumulates it into a datawarehouse". This
> is very error prone and we
> can't enforce all the constraints on all the various levels of human
> involvment to make
> all the data come out perfectly. Its especially true that the
> historical records can
> never be error corrected also. This is why the real estate business
> has Title Abstract
> companies always doing research to ok everything.
> Please help me understand whether I should logically model my
> business's real world
> or the ideal world.
> More specifics follow below.
> I have a PARCEL (i.e., piece of land) and each PARCEL has one OWNER
> (i.e., a person).
> Therefore I think I should model my database as having two entities
> and its in 3rd normal form.
> parcel id attribute owner id attribute
> parcel number attribute ownername attribute
> However my data source for parcels and owners comes from type written
> notes
> and ownername could be coming to me mispelled. The same person may
> own
> several parcels and each time his name could be mispelled differently.
> Furthermore,
> even after this database is constructed I will have no source of
> cleaning
> ownernames up, so as far as the database knows it can not assume one
> is the same as another or if its the same as 'JON SMITH'.
> My question is "For proper logical design and 3rd normal form,
> 1) is it right to leave the PARCEL and OWNER as separate entities
> or can I combine owners into parcels and end up with just one entity,
> since ownername are freehand? (I will always have exactly as many
> ownernames as parcels).
> 2) if I leave PARCEL and OWNER as separate and since ownername is
> not maintained cleanly (therefore there is a one to one relationship
> between PARCEL and OWNER), should/could I have the owner id U.I. be
> renamed and identical to the parcel id?
> Another way to point out my problem is to think about a Blockbuster
> movie rental model.
> What if I didn't hand out Customer membership cards (to determine)
> owners uniquely
> and people just signed their names (with errors or short names at
> times). And several
> people have the same name in the same family address so that won't
> help uniquely
> identify the customer
> Thanks in advance for any help.
Received on Fri Mar 07 2003 - 15:12:46 CET

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