tomtriple/leonardo

This is an experimental editor for Turtle

TURTLE

This is a JavaScript based editor for the RDF serialization language Turtle. I tested the editor only in Google Chrome. The editor uses ANTLR´s JavaScript backend to recognize input.

Features

• Browser based editing support (with contentEditable) with respect to syntax highlighting.
• Syntax highlighting with respect to syntax-/lexer-errors.
• Resynchronization after syntax-/lexer-errors.
• Code completion.

Semantic reasoning is currently not implemented.

Implementation overview for syntax highlighting and code completion

From the user input it generates a parse tree (not an AST!) and traverses that as part of a classic visitor strategy (Turtle.g). After that the generated code is being integrated in the editor. Editor integration involves two things: Replacing a fragment of turtle-code with generated code for the exact same (but syntaxhighlighted) code fragment but also preserving incorrect code for which there no representing node in the parse tree.

If the cursor position is at a position that refers to a prefix definition for a vocabulary it tries to show all components of that vocabulary e.g. all definitions from FOAF. In order to display a vocabulary in the appropriate way it´s a prerequisite to recognize and translate a vocabulary (now with an AST!) to a JavaScript datastructure (ASTBuildingTurtle.g and ASTWalker.g). This datastructure serves as the basis for syntax-highlighting. In this respect there are two things of note:

• A vocabulary can be deployed on any domain which is inherently incompatible with the Same Origin Policy. Code completion uses a local webserver to work around that restriction. The webserver component uses Sinatra and acts lika a proxy to the actual vocabulary resource. A nice replacement for this would use CORS to perform a lookup. CORS doesn´t need a local webserver.

• Indeed that ajax request itself is asynchronous but the callback handler needs to instantiate a new parser instance to perform the translation. To prevent a user from typical blocking effects I decided to implement that component with a WebWorker.

Starting the local webserver

If you want to use code completion you´ve to start a local webserver which uses Ruby 1.9 with Sinatra. If these dependencies are available just type "make s" to start the webserver.

If you don´t start the webserver you can still rely on syntax highlighting in the editor.

Screenshot