Jelf is a an IntelliJ IDEA plugin for the Twelf system.
  - IntelliJ IDEA is an open source IDE mostly popular with Java programmers.
  - Twelf is an implementation of the LF logical framework, the Elf constraint logic programming
    language and a meta-theorem prover for LF.

Jelf currently implements the following features, though they are far from bug-free yet:
  - Syntax highlighting
  - On-the-fly reporting of syntax errors
  - Indexing and search on Twelf declarations and files
  - Code completion
  - Go-to-declaration action
  - Renaming of declarations
  - Twelf compile and error reporting

The following IntelliJ IDEA shortcuts currently work on Twelf files and declarations:
  - Ctrl+Space (Code completion)
  - Ctrl+B, Ctrl+Click (Go to declaration)
  - Alt+F7 (Find usages)
  - Ctrl+Shift+F7 (Highlight usages)
  - Shift+F6 (Rename)
  - Ctrl+W, Ctrl+Shift+W (Select code fragment)
  - Alt+Up Arrow, Alt+Down Arrow (Previous/next declaration)
  - Alt+Delete (Safe delete)
  - Ctrl+Alt+N (Inline declaration)
  - Ctrl+F12 (File structure)
  - Ctrl+Shift+F9 (Compile -- feed file as input to Twelf)