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How to manage a list of things in n3 and convert it to XHTML

From: Karl Dubost <karl@w3.org>
Date: Sat, 3 Sep 2005 16:51:09 -0400
Message-Id: <A3DF0DD3-EDE7-47F1-9570-C0A1B6F1B669@w3.org>
To: www-archive@w3.org

This is an attempt to manage the list of open source software CMS in n3
     http://www.la-grange.net/cms

We used the DOAP Vocabulary designed by Edd Dumbill. Here's an  
example of a file in n3, a syntax of RDF to collect the information  
about each software.

Important: All of this would not have been possible without the  
enlightment given by Sean B. Palmer <http://infomesh.net/sbp/>

First a simple example of n3 file using the DOAP vocabulary with only  
two projects into it. The file is quite self describing. But let's  
there's something which is called a Project with a few metadata:

Project
     - description of the project
     - the page where we can download it
     - the homepage of the project
     - the license
     - the name of the project
     - the programming language of the project

Oh yes it's N3 then it doesn't matter the order in which you write  
the things. Then writing:

[ a :Project;
     :homepage <http://www.flutterby.com/software/newwwsboy/>;
     :name "Newwwsboy"^^XML:string; ].

or writing:

[ a :Project;
     :name "Newwwsboy"^^XML:string;
     :homepage <http://www.flutterby.com/software/newwwsboy/>; ].

is exactly the same.


ok the file with two software which are described.


# Open source CMS list in n3
# XHTML Version at: http://www.la-grange.net/cms
#

@prefix : <http://usefulinc.com/ns/doap#> .
@prefix XML: <http://www.w3.org/2001/XMLSchema#> .

[ a :Project;
     :description "Newwwsboy takes e-mail or text files as input and,  
using comments in HTML documents as a template, formats the e-mail  
and stuffs it into those documents."^^XML:string;
     :download-page <http://www.flutterby.com/software/newwwsboy/>;
     :homepage <http://www.flutterby.com/software/newwwsboy/>;
     :license <http://usefulinc.com/doap/licenses/bsd>;
     :name "Newwwsboy"^^XML:string;
     :programming-language "Perl"^^XML:string; ].

[ a :Project;
     :description "E-mail robot for adding news items to a  
webpage."^^XML:string;
     :download-page <http://www.daemon.de/HtnewsDownload>;
     :homepage <http://www.daemon.de/Htnews>;
     :license <http://usefulinc.com/doap/licenses/gpl>;
     :name "Htnews"^^XML:string;
     :programming-language "C"^^XML:string; ].

#ENDS

We would like to extract from this file some values to reuse them in  
an HTML file for example. For this we will use the program cwm[1]  
which has query built-in features. If you install cwm on your  
computer, be careful to have python and PyXML[2] installed.

I like to use n3 as a file format because it's easier to read for me  
than RDF. You can easily convert between this two syntax of RDF.  
Let's say you got a file in RDF: my_file.rdf

Convert RDF to n3
     cwm --rdf myfile.rdf --n3  > myfile.n3
Convert n3 to RDF
     cwm --n3  myfile.n3  --rdf > myfile.rdf

Now let's create a file of rules in n3 that will help us to query our  
cms.n3 file which has the list of projects. We want for now to  
extract the name of each project and put it into a "h2" element.

from cms.n3
     :name "Newwwsboy"^^XML:string;
to have
     <h2>Newwwsboy</h2>


The way to do that is

1. to query every Project

{ [ a doap:Project;

2. Take the name and put it in a variable NAME

     doap:name ?NAME;

3. To create a variable TEXT mixing the NAME and the HTML

?TEXT string:concat ("<h2>" ?NAME "</h2>\n")}

4. To ouput the result of TEXT in the order given by "001"

     => { "001" log:outputString ?TEXT} .


The full n3 file cms2html.n3 looks like:

# cms2html.n3
# to query cms.n3

@prefix : <#> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix string: <http://www.w3.org/2000/10/swap/string#> .

{ [ a doap:Project;
     doap:name ?NAME; ] .
     ?TEXT string:concat ("<h2>" ?NAME "</h2>\n)}

     => { "001" log:outputString ?TEXT} .
#ENDS

Then the command with cwm

     cwm cms.n3 cms2html.n3 --think --strings

The ouput is

<h2>Htnews</h2>
<h2>Newwwsboy</h2>



Let's say we want to query more than one variable and we want to add  
the description now

# cms2html.n3
# to query cms.n3

@prefix : <#> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix string: <http://www.w3.org/2000/10/swap/string#> .

{ [ a doap:Project;
     doap:name ?NAME;
     doap:description ?DESCRIPTION ] .
     ?TEXT string:concat ("<h2>" ?NAME "</h2>\n<p>" ?DESCRIPTION "</p> 
\n")}

     => { "001" log:outputString ?TEXT} .
#ENDS

Then the command with cwm

     cwm cms.n3 cms2html.n3 --think --strings

The ouput is

<h2>Htnews</h2>
<p>E-mail robot for adding news items to a webpage.</p>
<h2>Newwwsboy</h2>
<p>Newwwsboy takes e-mail or text files as input and, using comments  
in HTML documents as a template, formats the e-mail and stuffs it  
into those documents.</p>



This is a bit geeky, but you can foresee the principles. I'm pretty  
sure it would be possible to design an HTML templating system based  
on n3 rules and apply them to contents.



[1] http://www.w3.org/2000/10/swap/doc/cwm.html
[2] http://pyxml.sourceforge.net/


-- 
Karl Dubost - http://www.w3.org/People/karl/
W3C Conformance Manager
*** Be Strict To Be Cool ***
Received on Saturday, 3 September 2005 20:51:44 GMT

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