How to model an “is a” relationship in an ERD using Crow’s foot notation? I have to create an entity-relationship diagram (ERD) for an assignment. I am doing this in a particular drawing tool with the Crow’s Foot notation. There is however one thing I cannot figure out:


How would you present an “is a” hierarchy in Crow’s Foot notation?


Currently, I am showing this by means of a one-to-one relationship between the Product superentity type and its subtypes (Books, Papers, etc.). 


Is this the correct way to go or is it wrong? (I could not find any website talking about it).
In ER modeling, IsA relationships go by the name "generalization/specialization".  A search on this should give you a few pointers.  Diagramming this pattern requires using a notation that was originally called "Enhanced ER modeling", although it's been a long time since this extension was introduced.  

Here's the wikipedia article:

http://en.wikipedia.org/wiki/Enhanced_entity%E2%80%93relationship_model

and here are some sample diagrams, from googling "Enhanced ER Images"

https://www.google.com/search?q=enhanced+er+images&amp;rlz=1C1CHFX_enUS586US586&amp;espv=2&amp;biw=1600&amp;bih=775&amp;tbm=isch&amp;imgil=E75HgoIGspploM%253A%253B5D6WMu1kSMfWrM%253Bhttp%25253A%25252F%25252Fwww.siue.edu%25252F~dbock%25252Fcmis450%25252F4-eermodel.htm&amp;source=iu&amp;pf=m&amp;fir=E75HgoIGspploM%253A%252C5D6WMu1kSMfWrM%252C_&amp;usg=__MdUOOzgIiqsPSTBQjFkTyRuaAlQ%3D&amp;dpr=1&amp;ved=0CDEQyjc&amp;ei=TpMBVeDoKMOjgwSerIOYBg#imgdii=_

I generally use the triangle notation.