You can define the basic functionality of your web app by drawing some simple diagrams:
AmoixA will enable you to draw these diagrams online.
- A class diagram describes the data that's accessed through your web app
- Activity diagrams describe the business processes (workflow) that your data flow through
- A CRUD matrix defines the roles that users of your application can have, and which data users with these roles can Create, Read, Update and Delete
- The screen flow diagram shows which user interface screens the app has, and how users can navigate from one screen to another
Details of these diagrams, and their exact meaning, are described in the book Inleiding UML (in Dutch and German).
These diagrams are the AxiomA (Dutch for axiom) of your web app.