what is the status of this issue?
If you right-click on the file, what does the Open List of programs show? Is the Modeler listed there?
There are no file associations setup for the Modeler, so I'm thinking somehow the situation is confined to your machine and your OS settings.
The 'open with' list shows 'SQL Developer', and selecting this opens Data Modeler.
sounds like the OS is confused, i would re-set the default and browse back to associate it with SQLDev and not SQLDev DM
This is quite an old problem which I have seen with JDeveloper and SQLDeveloper so it may be framework related. I don't currently have both installed to check it out, but as it has been around a long time I doubt it has gone away.
SQL files would open in either JDeveloper or SQL Developer following the pattern Joop described. Java files would only ever open in JDeveloper. IIRC there was never a SQL file association for JDeveloper and SQLDeveloper was always the default.