The document summarizes Linked Data and how to deploy it using Virtuoso. It describes Linked Data principles like using URIs to identify real-world objects and exposing data on the web by linking URIs. It also explains how Virtuoso implements content negotiation and URL rewriting to inject Linked Data into the existing web by separating identity and representation of resources and serving different representations using SPARQL queries.

8. Slash URI Semantics Separating identification and naming from representation using Slash URIs

9. Hash URI Semantics Separating identification and naming from representation using Hash URIs

15. Content Negotiation Decision Table © 2009 OpenLink Software, All rights reserved 200 (OK) – return RDF based information resource < http://…/ALFKI> that describes the entity < http://…/ ALFKI#this> using N3, Turtle, RDF/XML etc. 303 (Redirect) to (X)HTML document describing entity <http://…/ALFKI#this>, or 404 or 406 (Not available) if one doesn’t exist Hash based URI (identifies an entity / object ID) <http://demo.openlinksw.com/Northwind/Customer/ALFKI#this> 200 (OK) – if an RDF information resource exists on the server 200 OK Web Resource URL <http://demo.openlinksw.com/Northwind/Customer/ALFKI> RDF Representation Requested (X)HTML Representation Requested URI Type URI 200 (OK) if an (X)HTML information resource (document) exists, or 404 or 406 (Not available) if one doesn’t exist For static descriptions of a Data Object: Assumes there are static HTML and RDF documents available to provide HTML and RDF representations of the customer entity ALFKI

17. Content Negotiation Decision Table © 2009 OpenLink Software, All rights reserved 200 (OK) – return RDF based information resource < http://…/ALFKI> that describes the entity < http://…/ ALFKI#this> (N3, RDF/XML etc.) You can use SPARQL DESCRIBE to deliver RDF based description 303 (Redirect) to (X)HTML document describing entity <http://…/ALFKI#this>, or 404 or 406 (Not available) if one doesn’t exist Hash based URI (identifies an entity / object ID) <http://demo.openlinksw.com/Northwind/Customer/ALFKI#this> 200 (OK) – if an RDF information resource exists on the server 200 OK Web Resource URL <http://demo.openlinksw.com/Northwind/Customer/ALFKI> RDF Representation Requested (X)HTML Representation Requested URI Type URI 200 (OK) if an (X)HTML information resource (document) exists, or 404 or 406 (Not available) if one doesn’t exist For dynamically derived descriptions of a Data Object using SPARQL DESCRIBE:

19. URL Rewriting – Example Pipeline © 2009 OpenLink Software, All rights reserved Last (must be last in processing chain)‏ For 406: Vary: negotiate, accept Alternates: {“ALFKI” 0.9 {type application/rdf+xml}} 200 (OK), or 406 (Not acceptable), or 303 redirect to a URL which can render the requested representation (text/html) | (*/*)‏ /Northwind/Customer/([^#]*)‏ Normal (order irrelevant)‏ None 303 redirect to a URL which DESCRIBEs the entity identified by the URI (text/rdf.n3) | (application/rdf.xml)‏ /Northwind/Customer/([^#]*)‏ Normal (order irrelevant)‏ None 200 or 303 depending on QoS rules configured for TCN None (i.e. default)‏ /Northwind/Customer/([^#]*)‏ Rule Processing Order HTTP Response Headers Rule HTTP Response Code HTTP Accept Header (Regex)‏ Source URI (Regex)‏

20. Content negotiation for RDF representation © 2009 OpenLink Software, All rights reserved

23. Conductor UI for URL Rewriter © 2009 OpenLink Software, All rights reserved RDF view for Northwind sample database: Rewriting rule for HTML requests

24. Conductor UI for URL Rewriter © 2009 OpenLink Software, All rights reserved RDF view for Northwind sample database: Rewriting rule for RDF/XML or N3 based resource description requests

25. Conductor UI for URL Rewriter © 2009 OpenLink Software, All rights reserved Defining the SPARQL query underpinning the ‘Destination Path Format’ of the RDF/XML / N3 rewriting rule – Automatically URL encoded when saved

28. URL Rewriting Process for RDF Requests © 2009 OpenLink Software, All rights reserved

29. URL Rewriting Process for HTML Requests © 2009 OpenLink Software, All rights reserved HTML requests are redirected via proxy /about/html to a rendering template - description.vsp description.vsp rendering of Customer entity <http://demo.openlinksw.com/Northwind/Customer/ALFKI#this>

32. Example Exported Rule Definitions © 2009 OpenLink Software, All rights reserved DB.DBA.VHOST_DEFINE ( lhost=>'*ini*', vhost=>'*ini*', lpath=>'/Northwind',ppath=>'/DAV/home/demo/', is_dav=>1, vsp_user=>'dba', ses_vars=>0, opts=>vector ('url_rewrite', 'demo_nw_rule_list1'), is_default_host=>0); DB.DBA.URLREWRITE_CREATE_RULELIST ( 'demo_nw_rule_list1', 1, vector ('demo_nw_rule1', 'demo_nw_rule2')); DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'demo_nw_rule1', 1, '(/[^#]*)',vector ('path'), 1, '/about/html/http://^{URIQADefaultHost}^%s', vector ('path'), NULL, '(text/html)|(*/*)', 0, 303, NULL); DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'demo_nw_rule2', 1, '(/[^#]*)', vector ('path'), 1, '/sparql?query=DESCRIBE+%%3Chttp%%3A//^{URIQADefaultHost}^%U%%23this%%3E+%%3Chttp%%3A//^{URIQADefaultHost}^%U%%3E+FROM+%%3Chttp%%3A//^{URIQADefaultHost}^/Northwind%%3E&format=%U', vector ('path', 'path', '*accept*'), NULL, '(text/rdf.n3)|(application/rdf.xml)', 0, NULL, NULL);

48. TCN Configuration - via Conductor UI © 2009 OpenLink Software, All rights reserved