Ideas

Just another ERD (Entity Relationship Diagram) tool.

Should have 2 layers one on top of the other:

• Logical layer (bottom)
• Physical (top)

Basically, I should be able to define 2 entities (tables) and then a relationship between the two. At the logical level nothing else happens while at the physical level, the child table would "acquire" an additional field which "solidify" the relationship between the two tables.

Must have the ability to define sub-schemas.

Use XML file for storage
-> 2 files (one for logical and one for physical) or just one with all the information?

If a DB is reverse engineered the physical layer is created first and the logical layer must be draw from it. If a schema is created from scratch the logical layer is created first and the physical layer is just an "enhamcement."

Use MVC (Model View Controller) or reread Patterns book for a good structure of the program. Data structure stays the same but entities and relationships can be displayed in several different ways.
I like the way Visio colors tables (you can give them a color and a transparency).

Read more about ERDs. Is there any theory behind the schema representation?