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  • %VOSWARNING% ---+ Evaluator's Guide to Linked Data Deployment %TOC% This guide will shows how to deploy Linked Data for Objects in an RDF Resource File (physical) or Linked Data Views (Virtual) * To include both from references with specific examples for Physical and Virtual Resources * to include Mapping Rules * the list to consist of: 1. 11 ways to get RDF into Virtuoso 2. SPARQL Optimization 3. Linked Data Deployment ---++ 11 ways to get RDF into Virtuoso ---+++ HTTP Post using Content-Type: application/sparql-query With POST can be accomplished SPARQL Insert/Update etc. The result is in the rdf_quad. With GET Methods you can get the triples which are saved. ---++++ Examples ---+++++ Example 1 1. Create a DAV collection xx for user demo with password demo. 1. Execute the following command: curl -i -d "INSERT { }" -u "demo:demo" -H "Content-Type: application/sparql-query" http://localhost:8890/DAV/xx/yy 1. The response should be: HTTP/1.1 201 Created Server: Virtuoso/05.00.3023 (Win32) i686-generic-win-32 VDB Connection: Keep-Alive Content-Type: text/html; charset=ISO-8859-1 Date: Fri, 28 Dec 2007 12:50:12 GMT Accept-Ranges: bytes MS-Author-Via: SPARQL Content-Length: 0 1. The result in the DAV/xx location will be a new WebDAV resource with name "yy" containing the following: * if opened with Conductor: CONSTRUCT { ?s ?p ?o } FROM WHERE { ?s ?p ?o } * if opened with GET, then the content will be RDF representation of what was inserted into the graph, i.e. ---+++++ Example 2 1. Create a DAV collection, for ex. with name "test" for user ( for ex. demo). 1. Execute the following command: curl -i -d "INSERT IN GRAPH { . . } " -u "demo:demo" -H "Content-Type: application/sparql-query" http://localhost:8890/DAV/home/demo/test/myrq 1. As result the response will be: HTTP/1.1 201 Created Server: Virtuoso/05.00.3023 (Win32) i686-generic-win-32 VDB Connection: Keep-Alive Content-Type: text/html; charset=ISO-8859-1 Date: Thu, 20 Dec 2007 16:25:25 GMT Accept-Ranges: bytes MS-Author-Via: SPARQL Content-Length: 0 1. Now let's check the inserted triples. Go to the sparql endpoint, i.e. http://localhost:8890/sparql and: * Enter for Default Graph URI: * Enter in the Query area: SELECT * WHERE {?s ?p ?o} * Click the button "Run Query" * As result will be shown the inserted triples: s p o Kingsley ---+++ HTTP PUT using Content-Type: application/rdf+xml The URI in a PUT request identifies the entity enclosed with the request. Therefore using HTTP PUT is a more useful and meaningful command than using POST (which is more about submitting data to a script). ---++++ Example 1. Suppose there is myfoaf.rdf file with the following content: Jose Jimen~ez Jo 1. Now let's upload the myfoaf.rdf file to destination server for user demo: curl -T myfoaf.rdf -u demo:demo 1. As result the response should be: 201 Created


    Resource /DAV/home/demo/rdf_sink/ myfoaf.rdf has been created.
    ---+++ SPARQL Insert using LOAD SPARQL INSERT operation can be done using the LOAD feature. Example: 1. Execute from ISQL: sparql insert in graph { . . . . . . . .}; 1. Create DAV collection which is visible to public, for ex: http://localhost:8890/DAV/tmp 1. Upload to the DAV collection the following file for ex. with name listall.rq and with the following content: PREFIX rdf: PREFIX rdfs: PREFIX sioc: SELECT ?x ?p ?o FROM WHERE { ?x rdf:type sioc:User . ?x ?p ?o. ?x sioc:id ?id . FILTER REGEX(str(?id), "^King") } ORDER BY ?x 1. Now from ISQL execute the following command: sparql load bif:concat ("http://", bif:registry_get("URIQADefaultHost"), "/DAV/tmp/listall.rq") into graph ; 1. As result should be shown: callret-0 VARCHAR _______________________________________________________________________________ Load into graph -- done 1 Rows. -- 321 msec. ---+++ SPARQL Insert via /sparql endpoint SPARQL INSERT operation can be sent to a web service endpoint as a single statement and executed in sequence. ---++++ Example Using the Virtuoso ISQL tool or using the /sparql UI at http://host:port/sparql, execute the following: * Insert into graph http://example/bookStore 3 triples: sparql insert in graph { <1999-04-01T00:00:00> . <1998-05-03T00:00:00> . <2001-02-08T00:00:00> }; * As result will be shown the message: Insert into , 3 triples -- done * Next we will select all triples from the graph http://example/bookStore: sparql select * from where {?s ?p ?o}; * As result will be shown: s p o VARCHAR VARCHAR VARCHAR _______________________________________________________________________________ 1998-05-03T00:00:00 2001-02-08T00:00:00 1999-04-01T00:00:00 3 Rows. -- 0 msec. * Now let's insert into graph another graph's values: sparql PREFIX dc: PREFIX xsd: INSERT INTO GRAPH { ?book ?p ?v } WHERE { GRAPH { ?book dc:date ?date FILTER ( xsd:dateTime(?date) < xsd:dateTime("2000-01-01T00:00:00")). ?book ?p ?v. } }; * As result will be shown: callret-0 VARCHAR _______________________________________________________________________________ Insert into , 2 triples -- done * Finally we will check the triples from the graph SQL> sparql select * from where {?s ?p ?o}; * As result will be shown: s p o VARCHAR VARCHAR VARCHAR _______________________________________________________________________________ 1998-05-03T00:00:00 1999-04-01T00:00:00 2 Rows. -- 10 msec. ---+++ SPARQL Insert via HTTP Post using Content-Type: application/sparql-query and ODS wiki With HTTP Post and ODS wiki can be written an rdf document and respectively to be performed over it INSERT/UPDATE action. You can write to a file using SIOC terms for ODS-Wiki. You can check with sparql the inserted / updated triples in the Quad Store. ---++++ Example 1. Suppose there is ODS user test3 with ODS password 1, which has testWiki wiki instance. 1. Execute the following: curl -i -d "INSERT { . . . . . . . . 'MyTest' . . }" -u "test3:1" -H "Content-Type: application/sparql-query" http://localhost:8890/DAV/home/test3/wiki/testWiki/MyTest 1. As result we should have 2 files created: * In the user DAV folder "DAV/home/test3/wiki/testWiki/" will be created a file "MyTest" with type "application/sparql-query". You can view the content of this file from from the Conductor UI or from the user's Briefcase UI, path "DAV/home/test3/wiki/testWiki". Its content will be: MyTest test * To the user's wiki instance will be added a new WikiWord "MyTest" with content the value of the SIOC term attribute "content": i.e. the content will be "test". 1. Now let's check what data was inserted in the Quad Store: * Go to the sparql endpoint, i.e. for ex. to http://localhost:8890/sparql * Enter for Default Graph URI: http://localhost:8890/DAV/home/test3/wiki/testWiki/MyTest * Enter for Query text: SELECT * WHERE {?s ?p ?o} * Click the "Run Query" button. * As result will be shown the inserted triples: s p o http://localhost:8890/dataspace/test3/wiki/testWiki http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest MyTest http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest test http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki http://localhost:8890/dataspace/test3/wiki/testWiki/MyTest http://localhost:8890/dataspace/test3/wiki/testWiki ---+++ Using Web DAV Example using WebDAV (mount folder to DAV and dump; if this is the rdf_sink the Quad Store is updated automatically, or you can load from DAV manually to quad store) ---++++ Examples ---+++++ Example 1: Using ODS Briefcase 1. Go to your ods location, for ex. http://localhost:8890/ods 1. Register user, for ex. user test1 1. Login if not already in ods 1. Go to ODS ->Briefcase 1. Create new instance 1. Go to the briefcase instance by clicking its name link 1. Upload file in a new created folder mytest or in the rdf_sink folder with: * checked option "RDF Store" * set RDF Graph Name, for ex. http://localhost:8890/DAV/home/test1/ of the current folder>/ for ex. http://localhost:8890/DAV/home/test1/mytest/ or http://localhost:8890/DAV/home/test1/rdf_sink/ * For ex. upload the following file with name jose.rdf. Jose Jimen~ez Jo 1. Execute the following query: select * from <> where {?s ?p ?o} 1. As result should be shown: s p o http://www.example/jose/foaf.rdf#jose http://www.example/jose/foaf.rdf#jose Jo http://www.example/jose/foaf.rdf#jose Jose Jimen~ez http://www.example/jose/foaf.rdf#jose http://www.example/jose/foaf.rdf#juan http://www.example/jose/foaf.rdf#jose http://www.example/jose/ http://www.example/jose/foaf.rdf#jose http://www.corp.example/ http://www.example/jose/foaf.rdf#kendall http://www.example/jose/foaf.rdf#edd http://www.example/jose/foaf.rdf#julia http://www.example/jose/foaf.rdf#julia mailto:julia@mail.example http://www.example/jose/foaf.rdf#juan http://www.example/jose/foaf.rdf#juan mailto:juan@mail.example ---+++++ Example 2: Using Conductor UI 1. Go to Conductor UI, for ex. at http://localhost:8890/conductor 1. Login as dba user 1. Go to WebDAV&HTTP and create new folder, for ex. test 1. Upload in the folder test a file, for ex. the file jose.rdf from above with options: * Destination: RDF Store * Set the RDF IRI ---+++ Using Virtuoso Crawler Using Virtuoso Crawler (which includes the Sponger options so you crawl non-RDF but get RDF and this can go to the Quad Store) ---++++ Example 1. Go to Conductor UI. For ex. at http://localhost:8890/conductor 1. Login as dba user 1. Go to tab WebDAV&HTTP 1. Go to tab Content Imports 1. Click the "New Target" button 1. In the shown form: * Enter for "Target description": Tim Berners-Lee's electronic Business Card * Enter for "Target URL": * Enter for "Copy to local DAV collection" for ex.: /DAV/home/demo/rdf_sink/ * Choose from the list "Local resources owner": demo * Check the with label "Store metadata". * Check all the check-boxes shown below the check-box "Store metadata". * Click the button "Create". * * Click the button "Import Queues". * For "Robot target" with label "Tim Berners-Lee's electronic Business Card" click the start link. * As result should be shown t he number of the pages retrieved. * 1. Now using the sparql endpoint with sponger option "Use only local data" enter for Default Graph URI: and execute the following query: select * where {?s ?p ?o} 1. As result should be shown the following triples: s p o Answers for young people - Tim Berners-Lee Berners-Lee: Weaving the Web Declaration by Tim BL 28 Feb 1996 w.r.t. CDA challenge Errata - Berners-Lee: Weaving the Web Frequently asked questions by the Press - Tim BL Glossary - Weaving the Web - Berners-Lee Longer Bio for Tim Berners-Lee Michael Dertouzos has left us The Future of the Web and Europe The World Wide Web: Past, Present and Future The World Wide Web: A very short personal history Tim Berners-Lee Tim Berners-Lee - 3Com Founders chair Tim Berners-Lee: Disclosures Tim Berners-Lee: WWW and UU and I Tim Berners-Lee: WorldWideWeb, the first Web client ---+++ Using SPARQL Query and Sponger (i.e. we Fetch the Network Resources in the FROM Clause or values for the graph-uri parameter in SPARQL protocol URLs) ---++++ Example 1. Execute the following query: sparql SELECT ?id FROM NAMED OPTION (get:soft "soft", get:method "GET") WHERE { GRAPH ?g { ?id a ?o } } limit 10; 1. As result will be shown the retrieved triples: id VARCHAR _______________________________________________________________________________ 10 Rows. -- 20 msec. ---+++ Using Virtuoso PL APIs ---++++ Example In the example script we implement a basic mapper which maps a text/plain mime type to an imaginary ontology, which extends the class Document from FOAF with properties 'txt:UniqueWords' and 'txt:Chars', where the prefix 'txt:' we specify as 'urn:txt:v0.0:'. use DB; create procedure DB.DBA.RDF_LOAD_TXT_META ( in graph_iri varchar, in new_origin_uri varchar, in dest varchar, inout ret_body any, inout aq any, inout ps any, inout ser_key any ) { declare words, chars int; declare vtb, arr, subj, ses, str any; declare ses any; -- if any error we just say nothing can be done declare exit handler for sqlstate '*' { return 0; }; subj := coalesce (dest, new_origin_uri); vtb := vt_batch (); chars := length (ret_body); -- using the text index procedures we get a list of words vt_batch_feed (vtb, ret_body, 1); arr := vt_batch_strings_array (vtb); -- the list has 'word' and positions array , so we must divide by 2 words := length (arr) / 2; ses := string_output (); -- we compose a N3 literal http (sprintf ('<%s> .\n', subj), ses); http (sprintf ('<%s> "%d" .\n', subj, words), ses); http (sprintf ('<%s> "%d" .\n', subj, chars), ses); str := string_output_string (ses); -- we push the N3 text into the local store DB.DBA.TTLP (str, new_origin_uri, subj); return 1; } ; -- delete from DB.DBA.SYS_RDF_MAPPERS where RM_HOOK = 'DB.DBA.RDF_LOAD_TXT_META'; insert soft DB.DBA.SYS_RDF_MAPPERS (RM_PATTERN, RM_TYPE, RM_HOOK, RM_KEY, RM_DESCRIPTION) values ('(text/plain)', 'MIME', 'DB.DBA.RDF_LOAD_TXT_META', null, 'Text Files (demo)'); -- here we set order to some large number so don't break existing mappers update DB.DBA.SYS_RDF_MAPPERS set RM_ID = 2000 where RM_HOOK = 'DB.DBA.RDF_LOAD_TXT_META'; 1. To test the mapper we just use /sparql endpoint with option 'Retrieve remote RDF data for all missing source graphs' to execute: select * from where { ?s ?p ?o } 1. To check the results: * Make sure the initial state of tutorial RD_S_1 is set. * Go to * Enter for Default Graph URI this value: http://localhost:80/tutorial/hosting/ho_s_30/WebCalendar/tools/summary.txt * Enter for Query text: select * where {?s ?p ?o} * Click the "Run Query" button. * As result should be shown the following triples: s p o http://localhost:80/tutorial/hosting/ho_s_30/WebCalendar/tools/summary.txt http://localhost:80/tutorial/hosting/ho_s_30/WebCalendar/tools/summary.txt urn:txt:v0.0:UniqueWords 47 http://localhost:80/tutorial/hosting/ho_s_30/WebCalendar/tools/summary.txt urn:txt:v0.0:Chars 625 Important: Setting Sponger Permissions: In order to allow the Sponger to update the local RDF quad store with triples constituting the Network Resource structured data being fetched, the role "SPARQL_UPDATE" must be granted to the account "SPARQL". This should normally be the case. If not, you must manually grant this permission. As with most Virtuoso DBA tasks, the Conductor provides the simplest means of doing this. ---+++ Using SIMILE RDF Bank API Virtuoso implements the HTTP-based Semantic Bank API that enables client applications to post to its RDF Triple Store. This method offers an alternative to using Virtuoso/PL functions or WebDAV uploads as the triples-insertion mechanism. ---++++ Example 1. From your machine go to Firefox->Tools->PiggyBank->My Semantic Bank Accounts 1. Add in the shown form: * For bank: address: * For account id: demo * For password: demo 1. Go to 1. Log in as user demo, password: demo 1. Go to the Weblog tab from the main ODS Navigation 1. Click on weblog instance name, for ex. "demo's Weblog". 1. When the weblog home page is loaded, click Alt + P. 1. As result is shown the "My PiggyBank" page with all the collected information presented in items. 1. For several of the items add Tags from the form "Tag" shown for each of them. 1. As result should be shown the message "Last updated: [here goes the date value]. 1. You can also click "Save" and "Publish" for these items. 1. Go to 1. Enter for the "Default Graph URI" field: 1. Enter for the "Query text" text-area: prefix rdf: prefix sioc: select * from where {?s ?p ?o} 1. Click "Run Query". 1. As results are shown the found results. ---+++ Using RDF NET ---++++ Example 1. Execute the following query: SQL> select DB.DBA.HTTP_RDF_NET ('sparql load "" into graph '); 1. As result should be shown: callret VARCHAR _______________________________________________________ Load into graph -- done 1 Rows. -- 1982 msec. ---++ Virtuoso Deploying Linked Data 1. Linked data: Describes recommended best practice for exposing & connecting data on the Semantic Web * Use the RDF data model * Identify real or abstract things (resources) in your ?universe of discourse? (Data Spaces), using URIs as unique IDs * Make URIs accessible via HTTP so people can discover and explore these Data Spaces * Allow these URIs to be dereferenced and return information * Include links to provide ?discovery paths? to entities in other Data Spaces 1. Document Web Resources: In the traditional Document Web: * All resources are document-orientated * URI dereferencing returns a document * Rendered representation is nearly always a document * No real distinction between a resource and its representation * Such resources have been referred to as ?information resources? 1. Semantic Web Resources: In the Semantic Web: * A URI identifies a thing (piece of data) in a data space * The identity of a thing is distinct from its address and representation * things may have several possible representations * the most desirable representation of a thing may change, depending on the consumer (human or software-agent) * things may be associated with data at different addresses within a data space * Unfortunately, URIs identifying things are generally referred to as ?non-information resources? in AWWW parlance * Entity or Object IDs, or Data Source Names, are preferable terms 1. Deployment Challenges: We?ve established that the Semantic Web and Linked Data require: * Data access with unambiguous naming * Data (de)reference with ambiguous association * Or put another way, we need mechanisms for an HTTP server to: * Answer the question ?Does this URI identify a (physical) document resource or an (RDF based) abstract entity/thing?? * Provide alternative representations of an entity/thing 1. Deployment Challenge Resolution: Two solutions proposed by the SemWeb Community: * Distinguish resource type through URL formats * ?Hash? vs ?slash? URLs * Content negotiation with URL rewriting 1. ?Hash? vs ?Slash? URLs: * A solution using the syntax of the URL to differentiate ?abstract? resources from ?information? resources * Slash URIs * Don?t contain a fragment identifier (#)? * Identify document resources in traditional Web * E.g. * Identifies a physical (X)HTML document * Hash URIs * Contain a fragment identifier * Identify data resources (entities) in Semantic Web * E.g. * Identifies the entity ALFKI, distinct from its representation 1. Content Negotiation - Example: 1. HTTP Request: * HTML browser requests a HTML/XHTML document in English or French GET /whitepapers/data_mngmnt HTTP/1.1 Host: Accept: text/html, application/xhtml+xml Accept-Language: en, fr * Accept header indicates preferred MIME types * RDF browser might instead stipulate a MIME type of application/rdf+xml or application/rdf+n3 1. HTTP Response: * Server redirects to a URL where the appropriate version can be found HTTP/1.1 302 Found Location: * Redirect is indicated by HTTP status code 302 (Found)? * Client then sends another HTTP request to the new URL * HTTP defines several 3xx status codes for redirection 1. Deploying Linked Data Using Virtuoso: * Virtuoso?s approach is to implement the generic solution outlined so far, using * Content negotiation * URL rewriting * Virtuoso includes a Rules-based URL Rewriter * Can be used to inject Semantic Web data into the Document Web 1. URL Rewriting Example: * URI dereferenced by RDF browser client or * becomes after rewriting (omitting URL encoding)? /sparql?query = CONSTRUCT { ?p ?o } FROM WHERE { ?p ?o } 1. URL Rewriting for iSparql: * iSparql Query Builder: e.g.Browsing Linked Data View: * Dereferencing: or * UI supports two commands for dereferencing a URI: * ?Explore? (i.e. Get all links to & from)? SELECT ?property ?hasValue ?isValueOf WHERE {{ ?property ?hasValue } UNION { ?isValueOf ?property }} ?Get Dataset? (i.e. Treat URI as a subgraph)? SELECT * FROM WHERE { ?s ?p ?o } 1. URL Rewriting for iSparql: Issues: * ?Get Dataset? Option ? Issues with URI being dereferenced: * Assumes URI is a named graph ? It isn?t! * It?s a unique node ID (object ID / entity instance ID)? * The only graph defined by our Linked Data View is: 1. Northwind URL Rewriting: The Aim: * Aim of URL rewriting for the Northwind Linked Data View: * Create a rule for RDF browsers which will map an IRI * to a SPARQL query CONSTRUCT ?p ?o FROM WHERE { ?p ?o } * and rewrite the request as /sparql?query=CONSTRUCT ... 1. Virtuoso - URL Rewriter Key Elements: 1. Rewriting Rule * Describes how to parse a ?nice? URL and compose the actual ?long? URL of the resource to be returned * Two types: sprintf-based and regex-based 1. Rewriting Rule List * Named, ordered list of rewriting rules or rule lists * Tried from top to bottom, first matching rule is applied 1. Conductor UI for rewriting rule configuration 1. Configuration API ? alternative to Conductor UI, for scripts * Functions for creating, dropping, enumerating rules & rule lists 1. URL Rewriter API: Enabling Rewriting: * Enabled through vhost_define( ) function * vhost_define( ) defines a virtual host or virtual path * opts parameter is a vector of field-value pairs * Field url_rewrite controls / enables URL rewriting * Field value is the IRI of the rule list to apply e.g. VHOST_DEFINE (lpath=>'/Northwind, ppath=>'/DAV/Northwind/', vhost=>?', lhost=>'', is_dav=>1, vsp_user=>'dba', is_brws=>0, opts=>vector ('url_rewrite', 'oplweb_rule_list1')); 1. URL Rewriter API: Summary: Functions in DB.DBA schema: URLREWRITE_CREATE_SPRINTF_RULE URLREWRITE_CREATE_REGEX_RULE URLREWRITE_CREATE_RULELIST URLREWRITE_DROP_RULE URLREWRITE_DROP_RULELIST URLREWRITE_ENUMERATE_RULES URLREWRITE_ENUMERATE_RULELISTS 1. URLREWRITE_CREATE_REGEX_RULE: URLREWRITE_CREATE_REGEX_RULE ( rule_iri, allow_update, nice_match, nice_params, nice_min_params, target_compose, target_params, target_expn := null, accept_pattern := null, do_not_continue := 0, http_redirect_code := null ) ; rule_iri: rule?s name / identifier nice_match: regex to parse URL into a vector of ?occurrences? nice_params: vector of names of the parsed parameters. Length of vector equals # of ?(?)? specifiers in the regex target_compose: ?compose? regex for the destination URL target_params: vector of names of parameters to pass to the ?compose? expression as $1, $2 etc target_expn: optional SQL text to execute instead of a regex compose accept_pattern: regex expression to match the HTTP Accept header do_not_continue: on a match, try / don?t try next rule in rule list http_redirect_code: null, 301, 302 or 303. 30x => HTTP redirect 1. URL Rewriter API ? Northwind Example: --Rewriting rule: DB.DBA.URLREWRITE_CREATE_REGEX_RULE ( 'oplweb_rule1?, 1, '([^#]*)?, vector('path'), 1, '/sparql?query=CONSTRUCT+{+%%3Chttp%%3A//}+FROM+%%3Chttp%%3A//{+%%3Chttp%%3A//}&format=%U?, vector('path', 'path', '*accept*'), null, '(text/rdf.n3)|(application/rdf.xml)', 0, 303); --In effect (omitting URL encoding): /sparql?query = CONSTRUCT { %U ?p ?o } FROM WHERE { %U ?p ?o } --where %U is a placeholder for the original URI * Arguments in previous rule defined by URLREWRITE_CREATE_REGEX_RULE: --nice_match arg: ([^#]*)? ----regex matches input IRI up to fragment delimiter --nice_params arg: vector('path')? ----?path? is name of first match group in nice_match regex --accept_pattern arg: (text/rdf.n3)|(application/rdf.xml)? ----regex to match HTTP Accept header --target_params arg: vector('path', 'path', '*accept*')? --names of params whose values will replace %U placeholders in the target URL pattern ---*accept* passes matched part of Accept header for substitution into &format=%U portion of query string e.g. application/rdf.xml * Enabling Rewriting: DB.DBA.URLREWRITE_CREATE_RULELIST ( 'oplweb_rule_list1', 1, vector ( 'oplweb_rule1' )); -- ensure a Virtual Directory /oplweb exists VHOST_REMOVE (lpath=>'/Northwind', vhost=>?', lhost=>''); VHOST_DEFINE (lpath=>'/Northwind', ppath=>'/DAV/Northwind/', vhost=>?', lhost=>'', is_dav=>1, vsp_user=>'dba', is_brws=>0, opts=>vector ('url_rewrite', 'oplweb_rule_list1')); 1. URL Rewriter - Verification with curl: * curl utility provides a useful tool for verifying HTTP server responses and rewriting rules $ curl -I -H "Accept: application/rdf+xml" HTTP/1.1 303 See Other Server: Virtuoso/05.00.3016 (Solaris) x86_64-sun-solaris2.10-64 PHP5 Connection: close Content-Type: text/html; charset=ISO-8859-1 Date: Tue, 14 Aug 2007 13:30:22 GMT Accept-Ranges: bytes Location: /sparql?query=CONSTRUCT+{+%3Chttp%3A// 23this%3E+%3Fp+%3Fo+}+FROM+%3Chttp%3A//{+%3C http%3A//}&format= application/rdf%2Bxml Content-Length: 0 1. URL Rewriter ? URIQADefaultHost Macro: * Makes rewriting rules (& Linked Data View definitions) more portable * Each occurrence is substituted with the value of the DefaultHost parameter in URIQA section of virtuoso.ini configuration file * DefaultHost ::= server name. e.g. '/sparql?query=CONSTRUCT+{+%%3Chttp%%3A//^{URIQADefaultHost}^%U%%23this%%3E+%%3Fp+%%3Fo+}+FROM+%%3Chttp%%3A//^{URIQADefaultHost}^/Northwind/%%3E+WHERE+{+%%3Chttp%%3A//^{URIQADefaultHost}^%U%%23this%%3E+%%3Fp+%%3Fo+}&format=%U' 1. Content Negotiation Revisited - TCN: Virtuoso supports two flavours of content negotiation: * HTTP/1.1 style content negotiation (introduced earlier) * Server-driven negotiation only * Transparent Content Negotiation (TCN) * Server-driven or agent-driven negotiation * Suitably enabled user agents / browsers can take advantage of TCN * Non-TCN capable user agents continue to be handled using HTTP/1.1 content negotiation 1. Transparent Content Negotiation: * Supports variant selection by user agent or by server * Transparent - all variants on server are visible to the agent * Variant Selection by User Agent: * User agent chooses best variant itself from variant list sent by server * Requires sending fewer/smaller Accept headers * Variant Selection by Server: * User agent can instruct server to select best variant on its behalf * Server uses ?remote variant selection algorithm? (RFC2296) 1. Example ? Preferred format: XML: * Assumes Virtuoso WebDAV server contains 3 variants of resource named ?page?: * /DAV/TCN/page.xml * /DAV/TCN/page.html * /DAV/TCN/page.txt * User agent indicates preference for XML $ curl -i -H "Accept: text/xml,text/html;q=0.7,text/plain;q=0.5,*/*;q=0.3" -H "Negotiate: *" HTTP/1.1 200 OK Server: Virtuoso/05.00.3021 (Linux) i686-pc-linux-gnu VDB Connection: Keep-Alive Date: Wed, 31 Oct 2007 15:44:07 GMT Accept-Ranges: bytes TCN: choice Vary: negotiate,accept Content-Location: page.xml Content-Type: text/xml ETag: "8b09f4b8e358fcb7fd1f0f8fa918973a" Content-Length: 39 some xml 1. Example ? Preferred format: HTML: * User agent indicates preference for HTML $ curl -i -H "Accept: text/xml;q=0.3,text/html;q=1.0,text/plain;q=0.5,*/*;q=0.3" -H "Negotiate: *" HTTP/1.1 200 OK Server: Virtuoso/05.00.3021 (Linux) i686-pc-linux-gnu VDB Connection: Keep-Alive Date: Wed, 31 Oct 2007 15:43:18 GMT Accept-Ranges: bytes TCN: choice Vary: negotiate,accept Content-Location: page.html Content-Type: text/html ETag: "14056a25c066a6e0a6e65889754a0602" Content-Length: 49 some html 1. Example ? Variant list request: * User agent asks for a list of variants $ curl -i -H "Accept: text/xml,text/html;q=0.7,text/plain;q=0.5,*/*;q=0.3" -H "Negotiate: vlist" http://localhost:8890/DAV/TCN/page HTTP/1.1 300 Multiple Choices Server: Virtuoso/05.00.3021 (Linux) i686-pc-linux-gnu VDB Connection: close Content-Type: text/html; charset=ISO-8859-1 Date: Wed, 31 Oct 2007 15:44:35 GMT Accept-Ranges: bytes TCN: list Vary: negotiate,accept Alternates: {"page.html" 0.900000 {type text/html}}, {"page.txt" 0.500000 {type text/plain}}, {"page.xml" 1.000000 {type text/xml}} Content-Length: 368 300 Multiple Choices

    Multiple Choices

    Available variants:
    1. TCN Configuration ? Variant Description * Variant descriptions held in SQL table HTTP_VARIANT_MAP * Added/updated/removed through Virtuoso/PL or Conductor UI create table DB.DBA.HTTP_VARIANT_MAP ( VM_ID integer identity, -- unique ID VM_RULELIST varchar, -- HTTP rule list name VM_URI varchar, -- name of requested resource e.g. 'page' VM_VARIANT_URI varchar, -- name of variant e.g. 'page.xml','' etc. VM_QS float, -- Source quality, number in the range 0.001-1.000, with 3 digit precision VM_TYPE varchar, -- Content type of the variant e.g. text/xml VM_LANG varchar, -- Content language e.g. 'en', 'de' etc. VM_ENC varchar, -- Content encoding e.g. 'utf-8', 'ISO-8892? etc. VM_DESCRIPTION long varchar, -- human readable variant description e.g. 'Profile in RDF format' VM_ALGO int default 0, -- reserved for future use primary key (VM_RULELIST, VM_URI, VM_VARIANT_URI) ) create unique index HTTP_VARIANT_MAP_ID on DB.DBA.HTTP_VARIANT_MAP (VM_ID) 1. TCN Configuration - via Virtuoso/PL: * Adding or Updating a Resource Variant DB.DBA.HTTP_VARIANT_ADD ( in rulelist_uri varchar, -- HTTP rule list name in uri varchar, -- Requested resource name e.g. 'page' in variant_uri varchar, -- Variant name e.g. 'page.xml', '' etc. in mime varchar, -- Content type of the variant e.g. text/xml in qs float := 1.0, -- Source quality, a floating point number with 3 digit precision in 0.001-1.000 range in description varchar := null, -- a human readable description of the variant e.g. 'Profile in RDF format' in lang varchar := null, -- Content language e.g. 'en', 'bg'. 'de' etc. in enc varchar := null -- Content encoding e.g. 'utf-8', 'ISO-8892' etc. ) * Removing a Resource Variant DB.DBA.HTTP_VARIANT_REMOVE ( in rulelist_uri varchar, -- HTTP rule list name in uri varchar, -- Name of requested resource e.g. 'page' in variant_uri varchar := '%' -- Variant name filter ) * Adding resource variant descriptions * Define variant descriptions & associate them with a rule list DB.DBA.HTTP_VARIANT_ADD ('http_rule_list_1', 'page', 'page.html', 'text/html', 0.900000, 'HTML variant'); DB.DBA.HTTP_VARIANT_ADD ('http_rule_list_1', 'page', 'page.txt', 'text/plain', 0.500000, 'Text document'); DB.DBA.HTTP_VARIANT_ADD ('http_rule_list_1', 'page', 'page.xml', 'text/xml', 1.000000, 'XML variant'); * Define a virtual directory & associate the rule list with it DB.DBA.VHOST_DEFINE (lpath=>'/DAV/TCN/', ppath=>'/DAV/TCN/', is_dav=>1, vsp_user=>'dba', opts=>vector ('url_rewrite', 'http_rule_list_1')); ---++ RDF sink folder support * [[VirtuosoRDFSinkFolder][Virtuoso RDF Sink Folder]] * [[ODSRDFSinkFolder][ODS RDF Sink Folder]] ---++ Making Rule Sets Since RDF Schema and OWL schemas are RDF graphs, these can be loaded into the triple store. Thus, in order to use such a schema as query context, one first loads the corresponding document into the triple store using ttlp or rdf_load_rdfxml or related functions. After the schema document is loaded, one can add the assertions therein into an inference context with the rdfs_rule_set function. This function specifies a logical name for the rule set plus a graph URI. It is possible to combine multiple schema graphs into a single rule set. A single schema graph may also independently participate in multiple rule sets. rdfs_rule_set (in name varchar, in uri varchar, in remove int := 0) This function adds the applicable facts of the graph into a rule set. The graph URI must correspond to the graph IRI of a graph stored in the triple store of the Virtuoso instance. If the remove argument is true, the specified graph is removed from the rule set instead. ---++ Changing Rule Sets Changing a rule set affects queries made after the change. Some queries may have been previously compiled and will not be changed as a result of modifying the rule set. When a rule set is changed, i.e. when rdfs_rule_set is called with the first argument set to a pre-existing rule set's name, all the graphs associated with this name are read and the relevant facts are added to a new empty rule set. Thus, if triples are deleted from or added to the graphs comprising the rule set, calling rdfs_rule_set will refresh the rule set to correspond to the state of the stored graphs. ---++ See Also * [[VirtLinkedDataDeploymentTutorialDOAP][Linked Data Deployment DOAP Tutorial]] ---++ References * [[][Linked Data Tutorial]] * [[VirtLinkedDataDeployment][ Deploying Linked Data in Virtuoso]] * Deploying RDF Linked Data via Virtuoso Universal Server * [[][PowerPoint Presentation]] * [[][Slidy(XHTML) ]] * [[][Slideshare]] * [[][Flash]] * [[][Google Doc]] * [[][RDF Database and SPARQL]] CategoryRDF CategoryVirtuoso
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