Open System Architect (OSA) is an application used for modelling a system. OSA currently supports data modelling (physical and logical) with UML in the works. The unique thing about OSA is that it is an Open Source product licensed under the General Public License (GPL). The free factor makes OSA particularly interesting for students but OSA is powerful enough to compare favourably with products costing thousands of dollars.
ERD (Logical & Physical)
ERD supports inheritance
ERD validation
UML in the works
SQL editor
workspace/project environment
cross-platform
cross-database
open source/open standards
GPL (free)
... and much more
