Solved

er diagrams and chen model

Posted on 2010-11-27
4
848 Views
Last Modified: 2012-05-10
Anyone have a good resource for learning how the chen model works in terms on relationship types.  Not sure when to use N or M,   when to use two lines,  etc

I also need to know of M:N is manay to many and is 1:N one to many

Looking for something that is easy to understand and has examples
0
Comment
Question by:enigma1234567890
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
4 Comments
 
LVL 44

Expert Comment

by:GRayL
ID: 34223273
0
 
LVL 44

Expert Comment

by:GRayL
ID: 34223274
In addition you might want to Google - Chen Model ERD
0
 
LVL 74

Accepted Solution

by:
Jeffrey Coachman earned 500 total points
ID: 34227685
1. Well, Chen wrote an article on entity-relationship modeling, but this and the other related concepts (ex.: Normalization) were around way before then.
(Google: Boyce Codd normal forms)

So the term "chen model" is just an attempt to reference this principle to a specific individual's famous work.

So just as "Boyce-Codd Normal form" is associated with Boyce and Codd, the same principles had existed prior to being "Named".

The same applies here for the "Chen Model"
*However* you must fully understand basic ERD, before you can begin to conceptualize the same things using "Chen Modeling"

2. <I also need to know of M:N is manay to many and is 1:N one to many>
Both of these statements are correct.
(Note that there is also 1:1, One To One)


3. Your original post states: "when to use two lines"
?
Can you be a bit more specific as to what you are trying to figure out.
(using a specific example)

If by "Two Lines" you mean as I have in the attached screenshot, ...then in terms of "Cardinality", this means: Mandatory Single
This is ERD Basic theory, and not specific to "Chen".
So again, you need to be familiar with Basic ERD theory and diagrams, then graduate to Chen.

;-)

JeffCoachman
untitled.JPG
0
 
LVL 74

Expert Comment

by:Jeffrey Coachman
ID: 34235161
;-)
0

Featured Post

Transaction Monitoring Vs. Real User Monitoring

Synthetic Transaction Monitoring Vs. Real User Monitoring: When To Use Each Approach? In this article, we will discuss two major monitoring approaches: Synthetic Transaction and Real User Monitoring.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Access developers frequently have requirements to interact with Excel (import from or output to) in their applications.  You might be able to accomplish this with the TransferSpreadsheet and OutputTo methods, but in this series of articles I will di…
Traditionally, the method to display pictures in Access forms and reports is to first download them from URLs to a folder, record the path in a table and then let the form or report pull the pictures from that folder. But why not let Windows retr…
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…
Add bar graphs to Access queries using Unicode block characters. Graphs appear on every record in the color you want. Give life to numbers. Hopes this gives you ideas on visualizing your data in new ways ~ Create a calculated field in a query: …

695 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question