HELP- Entity Relationship Diagrams

#1
HELP

Am doing my MSc in PMing and doing my IT bit, but come to a grinding halt on a question for my cse work. (the issued books are pants)

I need to do a ERM for the following:

a) a client prepares one or more contracts;
(b) a contract is prepared by one client;
(c) a client prepares one brief;
(d) a brief is prepared by one client;
(e) a client employs one or more contractors;
(f) each contractor is employed by the client;
(g) each contractor signs one contract; and
(h ) many contracts are signed by different contractors.

Will PM civi email for answer to be sent through!
Cheers PANTSOFF
 
#2
just a little bump!
 
#3
sounds like a tree type diagram to be solved in a lunchbreak
 
#4
Pantsoff - can you post the actual scenario statement / question - before I answer with complete borrix! Understand that you have the actions available to the various entities - Does the brief not instruct you what type of diagram you are meant to be producing? From the information you've given, there are at least half a dozen types of diagram that you could produce, but the choice would be easier to make, if it was clear what the object of the diagram is and who would be expected to use it.
 
#5
hi, it's all pretty straightforward. always note that relationships (in programming), are ideally one to one (1:1) or one to many (1:M). many to many (M:M) is a big NO NO. going by these, you can easily do your diagrams per scenario. if you find that you have a M:M relationship, make sure you break it down to a 1:M. make sure you use unique identifiers (ids) to identify your rows and your parent/child relationships.

therefore, your answers would be:
a) one client to many contracts is a 1:M relationship.
b) one contract to one client is a 1:1 relationship
etc, etc.

hope these help.
 
#6
Is this the sort of thing?
 

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#7
Pantsoff said:
a) a client prepares one or more contracts;
(b) a contract is prepared by one client;
(c) a client prepares one brief;
(d) a brief is prepared by one client;
(e) a client employs one or more contractors;
(f) each contractor is employed by the client;
(g) each contractor signs one contract; and
(h ) many contracts are signed by different contractors.
If I'm reading this correctly your entities are:
Clients
Contracts
Briefs
Contractors

Can Briefs and Contracts be treated as one item? Ie Brief A results in Contract proposals A1, A2, A3 and A4. A3 wins and is the one that is signed.
 
#8
looks good, msr. i'd like to add that contract and contractors seem to be a M:M relationship (fork to fork). i'm thinking this should be further broken down using an intermediate table, contract to contractor. in all tables, identify your columns, particularly your primary key, secondary key, etc. these help identify the parent/child relationships.
 
#9
It's a start. I'm not doing his homework for him ;)

Especially at M level.

msr
 
#11
Eeeh. Entity relationship diagrams. Here on ARRSE. Whatever next? I remember when that nice Dr Codd and I could look out the window and all you could see was fields.

If I was a bit younger and could understand such things, I might think that callgirl is right and you need to break the many to many between contracts and contractors with a link entity called something like 'project', giving the ERD shown below.

Now, damn this Alzheimers. Where did I leave me dentures?
 

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#12
Shows good leadership and researching qualities - Help me :)
 
#14
Entity Relationship Diagrams....

NOT what I was expecting to be honest.

I clicked on this thread with such hope/anticipation too... :oops:
 
#15
cali_girl said:
attention to details, please ancient_mariner. i'm NOT a callgirl ;)
Shame was going to ask for your number :)
 
#16
FFS - I've been teaching database all day - I come for a laff and a bevvy on ARRSE and...

Anyway to paraphrase Dr. Codd "The Key, the Whole Key and nothing but the Key"
 
#17
Thanks for the pointers chaps.
 
#19
Ancient_Mariner said:
cali_girl said:
attention to details, please ancient_mariner. i'm NOT a callgirl ;)
Oops. Sorry about that. Damn these old eyes. :oops:
Freudian Slips, eh? Had a feeling you'd get in shit for that one :D
 
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