kenwebb / xholon

Xholon

Xholon is an open-source library for making open-ended HTML5 client-side applications. The technology focus is on hierarchical and graph structure, building complex worlds, dynamic interactions, visualization, dynamic content updates, ...

Xholon uses Google Web Toolkit (GWT 2.8.2) to compile this repository's Java source code into a 100%-JavaScript library. The JavaScript API (with a jQuery-like syntax) enables writing web applications that run entirely in the browser.

Some of the numerous sample apps were written in Java, and some exist as XML and JavaScript Xholon Workbooks available as individual gist files. All of these apps run entirely in the browser with no ongoing need for a server.

Xholon is an online environment for exploring and playing around with things as diverse as the structure of a biological cell and the movements of characters in Lord of the Rings. Start by jotting down a few notes, progress to working out what the domain objects are and how they interact, and make it rock by writing some code.

It's all based on the idea that everything is connected. This makes Xholon difficult to describe, because there are so many ways that things can be connected. The best way to start learning is with the sample apps.

Hello World sample app

View the source code and run it, and then make a small edit in the source code and run it again.

Lord of the Rings sample app

View the source code and run it, and then make a small edit in the source code and run it again.

Other Links

Original Xholon site

Original Xholon wiki

Original Xholon Sourceforge project

Xholon Collaborative apps blog

Primordion site

Some apps where graphics are especially important

Interactive animations using d3 circle packing

xholon's Issues

JavaScript ANTLR4 grammar - Issues with quotes and comments

Hi,

I have downloaded the ANTLR4 grammar from:

https://www.opencypher.org/resources
https://s3.amazonaws.com/artifacts.opencypher.org/M14/Cypher.g4

I am able to process Cypher.g4 (JavaScript):

java -jar antlr-4.7-complete.jar -Dlanguage=JavaScript Cypher.g4

Antlr correctly generates five files:

 CypherLexer.js
 CypherLexer.tokens
 CypherListener.js
 CypherParser.js
 Cypher.tokens

My example web page (.html) includes the following JavaScript code:

  const antlr4 = require('xholon/lib/antlr4/index');
  const CypherLexer = require('xholon/lib/antlr4g/CypherLexer');
  const CypherParser = require('xholon/lib/antlr4g/CypherParser');
  const CypherListener = require('xholon/lib/antlr4g/CypherListener');
  const input = 'CREATE (fgh {ijk: 123.4})'; // OK
  const chars = new antlr4.InputStream(input);
  const lexer = new CypherLexer.CypherLexer(chars);
  const tokens  = new antlr4.CommonTokenStream(lexer);
  const parser = new CypherParser.CypherParser(tokens);
  const tree = parser.oC_Cypher();
  updateTree(tree); // this is where I run my own code

In this simple example CREATE (fgh {ijk: 123.4}), I then process the Cypher tree and get the results that I expect (it creates a new node in my application).

BUT, it fails to work with any Cypher statement that contains single quotes (ex: 'abc'), double quotes (ex: "def"), or comments (ex: // this is a comment). For example:

const input = "CREATE (fgh {ijk: 'This is some text.'})"; // error

or

const input = 'CREATE (fgh {ijk: "This is some text."})'; // error

ErrorListener.js (part of the ANTLR4 distribution) reports (in the browser console window):

line 1:18 token recognition error at: ''Th'
line 1:37 token recognition error at: ''}'
line 1:21 no viable alternative at input 'CREATE (fgh {ijk: is'

I have developed a temporary work-around by replacing content in Cypher.g4 with content from DOT.g4 (Graphviz dot language), which is included with the ANTLR4 distribution.
This lets me handle comments and double-quotes in openCypher, and allows me to continue exploring whether or not I will be able to use openCypher.

I hope this description of the issues I have found will be helpful,
Ken Webb