Web applications of GF

GF Summer School 2011

Thomas Hallgren

A quick look at some web applications

• See www.grammaticalframework.org/demos.
• Numeral translator, Letter editor (Java applets)
• Multilingual Wiki
• Fridge poetry, Word-completing translator (GWT)
• Minibar, Tourist Phrasebook, Mathbar, Translation Quiz (JavaScript)
• Syllogisms (JavaScript + Haskell + ...)
• GF online editor

Implementing web applications using GF

• Server side
• Client side

Server-side GF applications

• In Haskell:

  import PGF
  import favourite web service library from hackage
  main = ...

• PGF service API also available for other programming languages

PGF run-time library in Haskell

• readPGF          :: FilePath -> IO PGF
  
  linearize        :: PGF -> Language -> Tree -> String
  parse            :: PGF -> Language -> Category -> String -> [Tree]
  
  linearizeAll     :: PGF -> Tree -> [String]
  linearizeAllLang :: PGF -> Tree -> [(Language,String)]
  
  parseAll         :: PGF -> Category -> String -> [[Tree]]
  parseAllLang     :: PGF -> Category -> String -> [(Language,[Tree])]
  
  languages        :: PGF -> [Language]
  categories       :: PGF -> [Category]
  startCat         :: PGF -> Category
  

• More details

PGF run-time library in Haskell

See also GF book and slides

PGF web service API

• For (server-side) applications in other programming languages
• For client-side web applications in JavaScript
• Operations: grammar list, parse, linearize, translate, complete, random

GF JavaScript library

• PGF service access
  • pgf_online.js, support.js
  • Documentation: gf-web-api
• User interface
  • minibar_input.js: user input with magnets and completion
  • minibar_translations.js: display translations
  • minibar.js: complete Minibar web app
  • minibar_support.js, support.js: auxiliary functions
  • Documentation: minibar-api

Running the PGF service on your own server/computer

• pgf-http
  • Standalone HTTP Server included in GF distributions (>=3.2)
  • Copy your .pgf files to grammars under the document root shown when starting pgf-http
  • Open http://localhost:41296/ in your web browser
  • See also www.grammaticalframework.org/doc/gf-quickstart.html
• FastCGI
  • Lighttpd
  • Apache httpd

Using FastCGI with lighttpd

• Configuration included in GF source
• No special permissions are needed
• cd GF/src/server
  cabal install
  lighttpd -f lighttpd.conf
• Open http://localhost:41296/ in your web browser
• Copy your .pgf files to GF/src/io/gwt/www/grammars.

Using FastCGI with Apache httpd

• Included in Linux and Mac OS distributions
• Usually need administrator permissions to enable and configure the fastcgi module
• Compile as above (cd GF/src/server ; cabal install)
• Copy pgf-service to the fcgi-bin directory.
• Add to the appropriate Apache httpd configuration file:

  Action pgf-service /fcgi-bin/pgf-service
  AddHandler pgf-service .pgf
  
  <Directory /Library/WebServer/Documents/fcgi-bin>
  SetHandler fastcgi-script
  Options +ExecCGI
  </Directory>

Web applications without a web server

• Translating grammars to JavaScript, example:
  • gf -make --output-format=js FoodEng.gf FoodIta.gf
  • Limited functionality
• Minibar offline
  • Uses .pgf files directly.
  • PGF library translated from Haskell to JavaScript to be able to run in web browsers.
  • It's an experiment. It's inefficient, but it supports dependent types.
  • Next experiment: try GHCJS.

The End

Questions?