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+<!DOCTYPE HTML>
+<html>
+<head>
+<title>About: GF online editor for simple multilingual grammars</title>
+<link rel="stylesheet" type="text/css" href="editor.css" title="Cloud">
+<link rel="alternate stylesheet" type="text/css" href="molto.css" title="MOLTO">
+
+<link rel=author href="http://www.cse.chalmers.se/~hallgren/" title="Thomas Hallgren">
+
+<meta name = "viewport" content = "width = device-width">
+<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
+<meta charset="UTF-8">
+
+<script type="text/javascript" src="slideshow.js"></script>
+
+</head>
+
+<body>
+<h1>GF online editor for simple multilingual grammars</h1>
+
+<div class=right>
+  <div class=slideshow>
+    <img onload="start_slideshow(this,{delay:5,fade:0.3})" src="P/w1s.jpg" alt="[GF online editor screen shoot]">
+    <img class=hidden src="P/w2s.jpg" alt="[GF online editor screen shoot]">
+    <img class=hidden src="P/w3s.jpg" alt="[GF online editor screen shoot]">
+    <img class=hidden src="P/w4s.jpg" alt="[GF online editor screen shoot]">
+  </div>
+</div>
+<h2>Introduction</h2>
+
+Traditionally, <a href="http://www.grammaticalframework.org/">GF</a>
+grammars are created in a text editor and tested in the
+GF shell. Text editors know very little (if anything) about the syntax of
+GF grammars, and thus provide little guidance for novice GF users. Also, the
+grammar author has to download and install the GF software on his/her own
+computer.
+
+<p>
+In contrast, the
+<a href="."><em>GF online editor for simple multilingual grammars</em></a>
+is available online, making it easier to get started. All that
+is needed is a reasonably modern web browser. Even Android and iOS devices
+can be used.
+<p>
+The editor
+also guides the grammar author by showing a skeleton grammar file and
+hinting how the parts should be filled in. When a new part is added to the
+grammar, it is immediately checked for errors.
+
+<p>
+Editing operations are accessed by clicking on editing symbols embedded
+in the grammar display:
+<span class=more>+</span>=Add an item,
+<span class=delete>×</span>=Delete an item,
+<span class=edit>%</span>=Edit an item.
+These are revealed when hovering over items. On touch devices, hovering is
+in some cases simulated by tapping, but there is also a button at the bottom
+of the display to "Enable editing on touch devices" that reveals all editing
+symbols.
+
+<p>
+In spite of its name, the editor runs entierly in the web
+browser, so once you have opened the web page, you can
+<strong>continue editing</strong> grammars even while you are
+<strong>offline</strong>.
+
+<h3>Current status</h3>
+
+<p>
+At the moment, the editor supports only a small subset of the GF grammar
+notation.
+Proper error checking is done for abstract syntax, but not (yet) for concrete
+syntax.
+
+<p>
+The grammars created with this editor always consists of one file for the
+abstract syntax, and one file for each concrete syntax.
+
+<h4>Abstract syntax</h4>
+
+The supported abstract syntax corresponds to context-free grammars
+(no dependent types). The definition of an abstract syntax is limited to
+<ul>
+  <li>a list of <em>category names</em>,
+  <var>Cat<sub>1</sub></var> ; ... ; <var>Cat<sub>n</sub></var>,
+  <li>a list of <em>functions</em> of the form
+  <var>Fun</var> : <var>Cat<sub>1</sub></var> -> ... ->
+  <var>Cat<sub>n</sub></var>,
+  <li>and a <em>start category</em>.
+</ul>
+
+Available editing operations:
+<ul>
+  <li>Categories can be added, removed and renamed. When renaming a category,
+  occurences of it in function types will be updated accordingly.
+  <li>Functions can be added, removed and edited. Concrete syntaxes are updated
+  to reflect changes.
+  <li>Functions can be reordered using drag-and-drop.
+</ul>
+
+Error checks:
+
+<ul>
+  <li>Syntactically incorrect function definitions are refused.
+  <li>Semantic problem such as duplicated definitions or references to
+  undefined categories, are highlighted.
+</ul>
+
+<h4>Concrete syntax</h4>
+
+At the moment, the concrete syntax for a language <var>L</var> is limited to
+<ul>
+  <li>opening the Resource Grammar Library modules
+  <code>Syntax</code><var>L</var> and <code>Paradigms</code><var>L</var>,
+  <code>Lexicon</code><var>L</var> and <code>Extra</code><var>L</var>,
+  <li><em>linearization types</em> for the categories in the abstract syntax,
+  <li><em>linearizations</em> for the functions in the abstract syntax,
+  <li><em>parameter type definitions</em>,
+  <var>P</var> = <var>C<sub>1</sub></var> | ... |<var>C<sub>n</sub></var>,
+  <li>and <em>operation definitions</em>, <var>op</var> = <var>expr</var>,
+   <var>op</var> : <var>type</var> = <var>expr</var>,
+</ul>
+
+Available editing operations:
+<ul>
+  <li>The LHSs of the linearization types and linearizations are determined by
+  the abstract syntax and do not need to be entered manually.
+  The RHSs can
+  be edited.
+  <li>Parameter types can be added, removed and edited.
+  <li>Operation definitons can be added, removed and edited.
+  <li>Definitions can be reordered (using drag-and-drop)
+</ul>
+Also,
+
+<ul>
+  <li>When a new concrete syntax is added to the grammar, a copy of the
+  currently open concrete syntax is created, since copying and modifying
+  is usually easier than creating something new from scratch.
+  (If the abstract syntax is currently open, the new conrete syntax will
+  start out empty.)
+  <li>When adding a new concrete syntax, you normally pick one of the supported
+  languages from a list. The language code and the file name is determined
+  automatically. But you can also pick <em>Other</em> from the list and change
+  the language code afterwards to add a concrete syntax for a language
+  that is not in the list.
+</ul>
+
+Error checks:
+<ul>
+  <li>The RHSs in the concrete syntax are checked
+  for syntactic correctness by the editor as they are entered.
+  (TODO: the syntax of parameter types is not check at the moment.)
+  <li>Duplicated definitions are highlighted. Checks for other
+  semantic errors are delayed until the grammar is compiled.
+</ul>
+
+<h3>Compiling and testing grammars</h3>
+
+When pressing the <strong>Compile</strong> button, the grammar will be compiled
+with GF, and any errors not detected by the editor will be reported.
+If the grammar is free from errors the user can then
+test the grammar by clicking on links to the online GF shell, the Minibar or
+the Translation Quiz.
+
+<h3><img class=right src="P/1307545089_weather_04.png" alt="">
+<img class=right src="P/1306856253_weather_06.png" alt="">Grammars in the
+cloud</h3>
+
+While the editor normally stores grammars locally in the browser, it is also
+possible to store grammars in the cloud.  Grammars can be stored in the cloud
+just for backup, or to make them accessible from multiple devices.
+
+<p>
+There is no automatic synchronization between local grammars and the cloud.
+Instead, the user should press
+<img src="P/1306856253_weather_06.png" alt="[Cloud Upload]">
+to upload the grammars to the cloud, and press
+<img src="P/1307545089_weather_04.png" alt="[Cloud download]">
+to download grammars from the cloud. In both cases, complete grammars
+are copied and older versions at the destination will be overwritten.
+When a grammar is deleted, both the local copy and the copy in the cloud
+is deleted.
+
+<p>
+Each device is initially assigned to its own unique cloud. Each device can thus
+have its own set of grammars that are not available on other devices.  It is
+also possible to merge clouds and share a common set of grammars between
+multiple devices: when uploading grammars to the cloud, a link to this grammar
+cloud appears. Accessing this link from another device will cause the clouds of
+the two devices to be merged. After this, grammars uploaded from one of the
+devices can be downloaded on the other devices. Any number devices can join the
+same grammar cloud in this way.
+
+<p>
+<strong>Note</strong> that while it is possible to copy grammars between
+multiple devices, there is no way to merge concurrent edits from multiple
+devices. If the same grammar is uploaded to the
+cloud from multiple devices, the last upload wins. Thus the current
+implementation is suitable for a single user switching between different
+devices, but not recommended for sharing grammars between multiple users.
+
+<p>
+Also <strong>note</strong> that each grammar is assigned a unique identity
+when it is first created. Renaming a grammar does not change its identity.
+This means that name changes are propagated between devices like other changes.
+
+<h3>Example-based grammar writing</h3>
+
+This is work in progress...
+
+<h3>Future work</h3>
+
+This prototype gives an idea of how a web based GF grammar editor could work.
+While this editor is implemented in JavaScript and runs in the web browser,
+we do not expect to create a full implementation of GF that runs in the
+web browser, but let the editor communicate with a server running GF.
+<p>
+By developing a GF server with an appropriate API, it should
+be possible to extend the editor to support a larger fragment of GF,
+to do proper error checking and make more of the existing GF shell functionality
+accessible directly from the editor.
+<p>
+The current grammar cloud service is very primitive. In particular, it is not
+suitable for multiple users developing a grammar in collaboration.
+
+<h3>Related documents</h3>
+<ul>
+  <li><a href="http://www.grammaticalframework.org/~hallgren/Talks/GF/gf-ide.html">GF Grammar Development Tools</a>. Slides from a presentation at the MOLTO meeting in Göteborg, March 2011.
+  <li><a href="http://www.grammaticalframework.org/grammar-ide/">The GF Grammar IDE</a>. MOLTO deliverable.
+  <li><a href="http://www.grammaticalframework.org/compiler-api">The GF Grammar
+  Compiler API</a>. MOLTO deliverable.
+</ul>
+
+<hr>
+<div class=modtime><small>
+<!-- hhmts start --> Last modified: Fri Oct  7 14:06:14 CEST 2011 <!-- hhmts end -->
+  </small></div>
+<address>
+<a href="http://www.cse.chalmers.se/~hallgren/">TH</a>
+<img src="http://www.altocumulus.org/~hallgren/online.cgi?icon" alt="">
+</address>
+</body> </html>