catweb: A Web-based bird photo catalog |  |
catweb: A Web-based bird photo catalog | |
The overall structure of this catalog relates three entities:
Each photo may depict one or more forms of bird.
A form refers to all the photos that use a specific English name.
The external taxonomy system places each English name into a specific biological taxon.
Here is an entity-relationship diagram (ERD) for these three entities. If you are not familiar with ERD notation, see How to read ERDs.
The taxon object has a relationship to
itself: a taxon may or may not have a parent, and it may
have zero or more children. In short, taxon
objects are structured as a tree.
Taxa have a one-to-many relationship to forms: a taxon may contain photos for only one form, or for more than one.
Photos have a many-to-many relationship with forms. A single photo may depict more than one kind of bird; and the catalog may contain zero or more photos of a kind of bird.