Simple Linked Data Deployment using Virtuoso's HTTP Re-write Rules

What?

Use basic URL pattern as the basis for re-write rules that serve 5-Star Linked Data from a Virtuoso instance.

Why?

Linked Data offers a powerful mechanism for incorporating the connectivity of hyperlinks (typically HTTP URIs) into the process of actual structured data representation and data access.

How?

Perquisites:

The following example demonstrates the usage of a basic URL pattern as the basis for URL re-write rules.

Ensure Virtuoso's native faceted browser is installed so that you can leverage its entity description service via URL pattern: http://{hostname}/describe/?uri={URI}, for powerful HTML based follow-your-nose style of data exploration.

URL Pattern: http://{hostname}:8890/id/... Negotiated Data Representation formats to be handled by these rules:

1. text/html via "/page/" path component of the URL..
2. RDF (text/turtle, application/rdf+xml) via "/data/" path component of the URL .

-- Goals
-- Use slash terminated HTTP scheme URIs as Object Identifiers (Names) for Data Objects that resolve to Object Representations via a variety of URL patterns aligned to different data representation formats
-- Object IDs take the form /id while Object Representation Addresses take the form: /data .
--
-- Steps
-- Create URL re-write rules:
-- rules for HTML based Linked Data graphs

DB.DBA.URLREWRITE_CREATE_RULELIST ( 'http_rule_list_1', 1, vector ('http_rule_1', 'http_rule_2'));
DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'http_rule_2', 1, '/id/(.*)\x24', vector ('par_1'), 1, '/page/%s', vector ('par_1'), NULL, NULL, 2, 303, '' );

-- rules for other Linked Data Graph formats e.g. rdf/xml, n3

DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'http_rule_1', 1, '/id/(.*)\x24', vector ('par_1'), 1, '/data/%s', vector ('par_1'), NULL, 'text/n3|application/rdf\\+xml|text/rdf\\+n3', 2, 303, '' );

-- rules for Virtuoso Faceted Linked Data Navigation Service

-- rule: unconditionally we redirect "/page" URLs internally to "/describe" which is the default endpoint for the Faceted Navigation Service

DB.DBA.URLREWRITE_CREATE_RULELIST ( 'http_rule_list_2', 1, vector ('http_rule_3')); 
DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'http_rule_3', 1, '/page/(.*)\x24', vector ('par_1'), 1, '/fct/rdfdesc/description.vsp?g=http://localhost:8990/id/%s', vector ('par_1'), NULL, NULL, 2, 0, '' );


-- "/SPARQL" URL pattern handling rules that allow use of SPARQL DESCRIBE queries for generating and returning Linked Data Graphs in a variety of formats determined by HTTP request URL patterns.

-- query endpoints: http://localhost:8990/id/...> associated with "/data/" patterns

DB.DBA.URLREWRITE_CREATE_RULELIST ( 'http_rule_list_3', 1, vector ('http_rule_4')); 
DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'http_rule_4', 1, '/data/(.*)\x24', vector ('par_1'), 1, 
'/sparql?query=describe%%20%%3Chttp%%3A%%2F%%2Flocalhost%%3A8990%%2Fid%%2F%s%%3E%%20from%%20%%3Chttp%%3A%%2F%%2Flocalhost%%3A8990%%2Fdata%%2F%%3E&format=%U', 
vector ('par_1', '*accept*'), NULL, NULL, 2, 0, '' );


-- Virtual Directory Setup
-- Cleanup 
DB.DBA.VHOST_REMOVE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/id');

-- Create Virtual Directory that's associated with a named URL re-write rule for handling "/id" URL patterns
DB.DBA.VHOST_DEFINE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/id', ppath=>'/id/', is_dav=>0, def_page=>'', vsp_user=>'dba', opts=>vector ('url_rewrite', 'http_rule_list_1'));

-- do the same for "/page" URL patterns with use as Web Service endpoint for Virtuoso's Faceted Navigation Service in mind.
DB.DBA.VHOST_REMOVE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/page');
DB.DBA.VHOST_DEFINE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/page', ppath=>'/page/', is_dav=>0, def_page=>'', vsp_user=>'dba', opts=>vector ('url_rewrite', 'http_rule_list_2'));


-- do same for "/data" URL patterns with other Linked Data Graph formats in mind
DB.DBA.VHOST_REMOVE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/data');
DB.DBA.VHOST_DEFINE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/data', ppath=>'/data/', is_dav=>0, def_page=>'', vsp_user=>'dba', opts=>vector ('url_rewrite', 'http_rule_list_3'));

Using CURL to verify re-write rules

Example 1

curl -L -I  http://localhost:8990/id/state/MA 
HTTP/1.1 303 See Other
Server: Virtuoso/06.02.3129 (Win32) i686-generic-win-32  VDB
Connection: close
Content-Type: text/html; charset=ISO-8859-1
Date: Wed, 04 May 2011 13:44:24 GMT
Accept-Ranges: bytes
Location: http://localhost:8990/page/state/MA
Content-Length: 0

HTTP/1.1 200 OK
Server: Virtuoso/06.02.3129 (Win32) i686-generic-win-32  VDB
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8
Date: Wed, 04 May 2011 13:44:24 GMT
Accept-Ranges: bytes
Cache-Control: no-cache, must-revalidate
Pragma: no-cache
Link: <http://localhost:8990/sparql?query=define%20sql%3Adescribe-mode%20%22LOD%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost%3A8
3E&output=application%2Frdf%2Bxml>; rel="alternate"; type="application/rdf+xml"; title="Structured Descriptor Document (RDF/XML
host:8990/sparql?query=define%20sql%3Adescribe-mode%20%22LOD%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost%3A8990%2Fid%2Fstate%2F
>; rel="alternate"; type="text/n3"; title="Structured Descriptor Document (N3/Turtle format)",<http://localhost:8990/sparql?quer
ibe-mode%20%22LOD%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost%3A8990%2Fid%2Fstate%2FMA%3E&output=application%2Frdf%2Bjson>; rel
plication/rdf+json"; title="Structured Descriptor Document (RDF/JSON format)",<http://localhost:8990/sparql?query=define%20sql%3
D%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost%3A8990%2Fid%2Fstate%2FMA%3E&output=application%2Fatom%2Bxml>; rel="alternate"; ty
ml"; title="Structured Descriptor Document (OData/Atom format)",<http://localhost:8990/sparql?query=define%20sql%3Adescribe-mode
RIBE%20%3Chttp%3A%2F%2Flocalhost%3A8990%2Fid%2Fstate%2FMA%3E&output=application%2Fodata%2Bjson>; rel="alternate"; type="applicat
="Structured Descriptor Document (OData/JSON format)",<http://localhost:8990/sparql?query=define%20sql%3Adescribe-mode%20%22LOD%
http%3A%2F%2Flocalhost%3A8990%2Fid%2Fstate%2FMA%3E&output=text%2Fcxml>; rel="alternate"; type="text/cxml"; title="Structured Des
 format)",<http://localhost:8990/sparql?query=define%20sql%3Adescribe-mode%20%22LOD%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost
FMA%3E&output=text%2Fcsv>; rel="alternate"; type="text/csv"; title="Structured Descriptor Document (CSV format)",<http://localho
rel="http://xmlns.com/foaf/0.1/primaryTopic",<http://localhost:8990/id/state/MA>; rev="describedby"
Content-Length: 10858

Example 2

curl -L -I -H "Accept: text/n3"  http://localhost:8894/id/state/MA 
HTTP/1.1 303 See Other
Server: Virtuoso/06.02.3129 (Win32) i686-generic-win-32  VDB
Connection: close
Content-Type: text/html; charset=ISO-8859-1
Date: Wed, 04 May 2011 13:46:25 GMT
Accept-Ranges: bytes
Location: http://localhost:8990/page/state/MA
Content-Length: 0

HTTP/1.1 303 See Other
Server: Virtuoso/06.02.3129 (Win32) i686-generic-win-32  VDB
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8
Date: Wed, 04 May 2011 13:46:25 GMT
Accept-Ranges: bytes
TCN: choice
Vary: negotiate,accept
Location: http://localhost:8990/sparql?query=define%20sql%3Adescribe-mode%20%22LOD%22%20%20DESCRIBE%20%3Chttp%3A%2F%2Flocalhost%
MA%3E&format=text%2Fn3
Content-Length: 0

HTTP/1.1 200 OK
Server: Virtuoso/06.02.3129 (Win32) i686-generic-win-32  VDB
Connection: Keep-Alive
Date: Wed, 04 May 2011 13:46:25 GMT
Accept-Ranges: bytes
Content-Type: text/n3; charset=UTF-8
Content-Length: 15

Related

• Virtuoso Tips and Tricks Collection
• Virtuoso Faceted Browser Installation and Configuration Guide
• Virtuoso Faceted Search & Find Engine User Guide
• Faceted Navigation to Explore Virtuoso hosted Linked Data Usage Guide