Trivial ques-Resolving a Many-to-Many (m:n) Relationship..why reqd

Hi,

This is a very basic cinfusion which I am having.

I have a scenario where the 2 entities are having many to many relationship,I see that it is must to resolve these relationships.

Example : A Fax number directory Entity 1: Person details,Entity 2: Fax numbers,now here a person can be associated with more than one fax numeber and a fax number can be associated with more than one person.

Model 1)
So the entity as of now looks like
E1 (person_id(pk) ,let's assume this makes it unique...other columns)
E2(fax_num(pk),person_id(fk)...other columns)

It is suggested to have another intersection entity E3 and the new relationships will look like

Model 2)
E1 (person_id(pk) ,let's assume this makes it unique...other columns)
E3 (fax_num(pk)(fk),person_id(pk)(fk))
E2(fax_num(pk)... other columns)

Now my question is what if we keep the Model 1) as it is and just make the person_id in E2 as part of the primary key like E2(fax_num(pk),person_id(pk)(fk)...other columns)...may be I am little confused,but to me it looks fine...anyone please comment and give the answer.

All of the other columns in your fax entity are repeated for every person that owns that fax number. With model 1 if an attribute of the Fax entity changes, I will need to update multiple rows.