%META:TOPICPARENT{name="VirtTipsAndTricksGuide"}%
---+ Troubleshooting Linked Data Views generated from a Relational Database

---++What?

Virtuoso provides powerful options for generating 5-Star Linked Data from ODBC and JDBC accessible RDBMS based data sources. It provides you with the ability to produce transient and materialized Linked Data views using its native Metaschema Language or the W3C's R2RML.

---++Why?

Being able to diagnose problems associated with Linked Data views generation is vital for sustainable usage of this powerful Virtuoso feature. 

---++How?

The following steps guide you through the process of generating Linked Data Views and isolating problems that might arise during the process:

   1 Pick an example script building your view, in this case we use one that builds [[VirtTipsAndTricksLinkedDataViewsDB2Script][Linked Data Views from the DB2 hosted data]].
   1 It might happen that while running the script you receive [[VirtTipsAndTricksLinkedDataViewsDB2ScriptOutput][output]] errors such as:
<verbatim>
22023 The quad storage "http://www.openlinksw.com/schemas/virtrdf#DefaultQuadStorage" is edited by other client, started 2011-12-19 16:20:48
</verbatim>
   1 The error above means that a manipulation was started at 2011-12-19 16:20:48, but it never completed. The default remedy is to use Virtuoso's <code>[[http://docs.openlinksw.com/virtuoso/fn_rdf_audit_metadata.html][DB.DBA.RDF_AUDIT_METADATA()]]</code> function, as follows:
<verbatim>
SQL> DB.DBA.RDF_AUDIT_METADATA(1, '*');
</verbatim>
   1 The resulting output should contain no errors.
   1 Some demo links from the created Linked Data Views:
%BR%%BR%
      * Instance Data Named Graph
         * <code>[[http://demo.openlinksw.com/DB2HUGH#][http://demo.openlinksw.com/DB2HUGH#]]</code>
%BR%%BR%
      * Metadata Data ([[http://www.w3.org/TR/void/][VoID]])
         * <code>[[http://demo.openlinksw.com/DB2HUGH/stat#][http://demo.openlinksw.com/DB2HUGH/stat#]]</code>
%BR%%BR%
      * Ontology Data Named Graph
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/][http://demo.openlinksw.com/schemas/DB2HUGH/]]</code>
%BR%%BR%
      * Quad Maps
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-cl_sched][http://demo.openlinksw.com/schemas/DB2HUGH/qm-cl_sched]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-department][http://demo.openlinksw.com/schemas/DB2HUGH/qm-department]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-employee][http://demo.openlinksw.com/schemas/DB2HUGH/qm-employee]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_act][http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_act]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_photo][http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_photo]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_resume][http://demo.openlinksw.com/schemas/DB2HUGH/qm-emp_resume]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-in_tray][http://demo.openlinksw.com/schemas/DB2HUGH/qm-in_tray]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-org][http://demo.openlinksw.com/schemas/DB2HUGH/qm-org]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-project][http://demo.openlinksw.com/schemas/DB2HUGH/qm-project]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-sales][http://demo.openlinksw.com/schemas/DB2HUGH/qm-sales]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-staff][http://demo.openlinksw.com/schemas/DB2HUGH/qm-staff]]</code>
         * <code>[[http://demo.openlinksw.com/schemas/DB2HUGH/qm-VoidStatistics][http://demo.openlinksw.com/schemas/DB2HUGH/qm-VoidStatistics]]</code>
%BR%%BR%
      * Sample URIs
         * <code>[[http://demo.openlinksw.com/DB2HUGH/department/DEPTNO/A00#this][http://demo.openlinksw.com/DB2HUGH/department/DEPTNO/A00#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/employee/EMPNO/000010#this][http://demo.openlinksw.com/DB2HUGH/employee/EMPNO/000010#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/emp_act/EMPNO/000010/PROJNO/MA2100/ACTNO/10#this][http://demo.openlinksw.com/DB2HUGH/emp_act/EMPNO/000010/PROJNO/MA2100/ACTNO/10#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/emp_photo/EMPNO/000130/PHOTO_FORMAT/bitmap#this][http://demo.openlinksw.com/DB2HUGH/emp_photo/EMPNO/000130/PHOTO_FORMAT/bitmap#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/emp_resume/EMPNO/000130/RESUME_FORMAT/ascii#this][http://demo.openlinksw.com/DB2HUGH/emp_resume/EMPNO/000130/RESUME_FORMAT/ascii#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/org/DEPTNUMB/10/MANAGER/160#this][http://demo.openlinksw.com/DB2HUGH/org/DEPTNUMB/10/MANAGER/160#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/project/PROJNO/AD3100#this][http://demo.openlinksw.com/DB2HUGH/project/PROJNO/AD3100#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/sales/SALES_DATE/1995-12-31T05:00:00Z/SALES_PERSON/LUCCHESSI/REGION/Ontario-South/SALES/1#this][http://demo.openlinksw.com/DB2HUGH/sales/SALES_DATE/1995-12-31T05:00:00Z/SALES_PERSON/LUCCHESSI/REGION/Ontario-South/SALES/1#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/staff/ID/10#this][http://demo.openlinksw.com/DB2HUGH/staff/ID/10#this]]</code>
         * <code>[[http://demo.openlinksw.com/DB2HUGH/stat#][http://demo.openlinksw.com/DB2HUGH/stat#]]</code>


---++Related

   * [[VirtTipsAndTricksGuide][Virtuoso Tips and Tricks Collection]]
   * [[VirtTipsAndTricksRDFTriggers]["Generate RDB2RDF triggers" and "Enable Data Syncs with Physical Quad Store" Linked Data Views options]]
   * [[VirtTipsAndTricksGuideConductorR2RML][Generate Transient and/or Persistent Linked Data Views atop ODBC or JDBC accessible Relational Data Sources]]
   * [[VirtTipsAndTricksGuideOWLIinfLinkedVocab][Using OWL based inference to exploit the power of Linked Vocabularies]]
   * [[VirtTipsAndTricksImportLinkedDataCreateFeature][Import Linked Data using the Briefcase "Create" feature]]
   * [[VirtTipsAndTricksInstallPattern][Simple Linked Data Deployment using Virtuoso's HTTP Re-write Rules]]
   * [[VirtTipsAndTricksGuideReificationAltern][Reification alternatives usage for Linked Data publishing]]
   * [[VirtTipsAndTricksGuideLinkedDataSimpleGuide][Virtuoso Linked Data Deployment In 3 Simple Steps]]
   * [[VirtXMLAODBCExplorerLinkedDataViews][Expose Linked Data View URIs associated with "References" on a given Table]]
   * [[VirtLinkedDataPresCollection][Manage Linked (Open) Data]]