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