ERD dotted line.

In an entity relationship diagram what does it mean when there is a dotted line between two entities.
Mr_ShawAsked:
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Raja Jegan RSQL Server DBA & Architect, EE Solution GuideCommented:
A dotted line shows that an entity occurrence may be associated with each occurrence of the other entity.
An example Below with more references:

http://www.getahead-direct.com/gwentrel.htm
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dportasCommented:
Usually it means the relationship is non-identifying. In relational terms, the foreign key is not part of the primary key of the referencing table.
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Mr_ShawAuthor Commented:
So a solid line indicates that an enitity is associated with each occurence as apposed to 'may be'?
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Mr_ShawAuthor Commented:
Is it true to say that the table created in 2NF would take dotted lines.
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dportasCommented:
A solid line means an identifying relationship. In other words the child entity cannot be indentified without its parent. In relational terms that means the foreign key is part of the primary key (or possibly any candidate key - I'm not sure that it really matters).
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mrjoltcolaCommented:
dotted = optional
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Mr_ShawAuthor Commented:

So a solid line represents parent child relationship.

Therefore a dotted line is NOT a parent child relationship.

This must mean that a dotted line show that each entity does not depend on the other....therefore optional.  

For example members phone number, and address could be optional and could be in a entity which is joined with a dotted line?
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dportasCommented:
A dotted line could be a parent child relationship too.

You are right that if a member's phone number and address is optional then the relationship to address and phone number is non-identifying and would be pictured as a dotted line.
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Mr_ShawAuthor Commented:
thanks
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