Re: weak entity

In message <gcFp9.923$US2.10606_at_vixen.cso.uiuc.edu>, Ashutosh Galande <galande_at_uiuc.edu> writes
>I totally agree with you. But what I don't understamd is, if adding external
>ID attribute to inherent attributes of an entity doesn't make it strong
>entity then we are fraught with a number of weak entities in real life. I
>have seen it to be a common practice to use ID attribute for entities. These
>attributes, as you noted are generated with additional processing outside
>the database. But still the ER diagram represents these entities as a strong
>entity. So why this anomaly?

The diagram is wrong, or at least misleading. What it should really show is the same weak entity plus a new strong entity with one attribute, the ID. There should be a 1:1 relationship between the new entity and the weak entity.

I think it's probably better to represent entities like this because it should remind system designers that the 1:1 relationship has to be maintained.

-- 
Bernard Peek
bap_at_shrdlu.com
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