1.2 PGF Service Requests

The GF Cloud Service supports a set of PGF service requests, for example, a request like

http://cloud.grammaticalframework.org/grammars/Foods.pgf?command=random

might return a result like

[{"tree":"Pred (That Pizza) (Very Boring)"}]

The PGF Service in the GF Cloud is the application which exposes the PGF API as Web Service. The application uses FastCGI as communication protocol to talk with the web server. The data protocol that we use is JSON. Information for how to compile and install the service could be found here.

A compiled GF grammars could be used in web applications in the same way as JSP, ASP or PHP pages are used. The compiled PGF file is just placed somewhere in the web site directory. When there is a request for access to a .pgf file then the web server redirects the request to the GF web service. The service knows how to load the grammar and interpret the parameters given in the URL.

If my_grammar.pgf is a grammar placed in the root folder of the web site for localhost then the grammar could be accessed using this URL:

http://localhost/my_grammar.pgf

Since there aren't any parameters passed in this case, the web service will respond with some general information about the grammar, encoded in JSON format. To perform specific command you have to tell what command you want to perform. The command is encoded in the parameter command i.e.:

http://localhost/my_grammar.pgf?command=cmd

where cmd is the name of the command. Usually every command also requires specific list of other arguments which are encoded as parameters as well. The list of all supported commands follows:

Commands

Grammar

This command provides some general information about the grammar. This command is also executed if no command parameter is given.

Input

Output

Object with three fields:

Every language is described with object having this two fields:

The language codes should be specified in the grammar because they are used to identify the user language. The web service receives the code of the language set in the browser and compares it with the codes defined in the grammar. If there is a match then the service returns the corresponding concrete syntax name. If no match is found then the first language in alphabetical order is returned.

Parsing

This command parses a string and returns a list of abstract syntax trees.

Input

Output

List of objects where every object represents the analyzes for every input language. The objects have three fields:

The abstract syntax trees are sent as plain strings. The type errors are objects with two fields:

The current implementation either returns a list of abstract syntax trees or a list of type errors. By checking whether the field trees is not null we check whether the type checking was successful.

Linearization

The command takes an abstract syntax tree and produces string in the specified language(s).

Input

Output

Translation

The translation is a two step process. First the input sentence is parsed with the source language and after that the output sentence(s) are produced via linearization with the target language(s). For that reason the input and the output for this command is the union of the input/output of the commands for parsing and the one for linearization.

Input

Output

The output is a list of objects with these fields:

Every translation is an object with two fields:

Every linearization is an object with two fields:

The type errors are objects with two fields:

The current implementation either returns a list of translations or a list of type errors. By checking whether the field translations is not null we check whether the type checking was successful.

Random_Generation

This command generates random abstract syntax tree where the top-level function will be of the specified category. The categories for the sub-trees will be determined by the type signatures of the parent function.

Input

Output

The output is a list of objects with only one field:

The length of the list is limited by the limit parameter.

Word_Completion

Word completion is a special case of parsing. If there is an incomplete sentence then it is first parsed and after that the state of the parse chart is used to predict the set of words that could follow in a grammatically correct sentence.

Input

Output

The output is a list of objects with two fields which describe the completions.

Abstract Syntax Tree Visualization

This command renders an abstract syntax tree into image in PNG format.

Input

Output

Byy default, the output is an image in PNG format. The content-type is set to image/png, so the easiest way to visualize the generated image is to add HTML element <img> which points to URL for the visualization command i.e.:

<img src="http://localhost/my_grammar.pgf?command=abstrtree&tree=..."/>

The output can also be in GIF ('image/gif'), SVG ('image/svg+xml') or GV (graphviz) format by setting the 'format' option

Parse Tree Visualization

This command renders the parse tree that corresponds to a specific abstract syntax tree. The generated image is in PNG format.

Input

The additioal rendering options are: noleaves, nofun and nocat (booleans, false by default); nodefont, leaffont,nodecolor, leafcolor, nodeedgestyle and leafedgestyle (strings, have builtin defaults).

Output

By default, the output is an image in PNG format. The content-type is set to 'image/png', so the easiest way to visualize the generated image is to add HTML element <img> which points to URL for the visualization command i.e.:

<img src="http://localhost/my_grammar.pgf?command=parsetree&tree=..."/>

The output can also be in GIF ('image/gif'), SVG ('image/svg+xml') or gv (graphviz) format by setting the format option

Word Alignment Diagram

This command renders the word alignment diagram for some sentence and all languages in the grammar. The sentence is generated from a given abstract syntax tree.

Input

Output

By default, the output is an image in PNG format. The content-type is set to 'image/png', so the easiest way to visualize the generated image is to add HTML element `` which points to URL for the visualization command i.e.:

<img src="http://localhost/my_grammar.pgf?command=alignment&tree=..."/>

The output can also be in GIF ('image/gif'), SVG ('image/svg+xml') or GV (graphviz) format by setting the 'format' option