Replication Example: Star Topology

Introduction
Prerequisites

Database INI Parameters
Database DSNs
Install Conductor package

Create a Publication on the Host Virtuoso Instance -- db1
Insert Data into a Named Graph on the Host Virtuoso Instance
Subscribe to the Publication on the a Destination Virtuoso Instance -- db2, db3, etc.
Insert Triples into the Host Virtuoso Instance Graph and check availability at Destination Virtuoso Instance Graph
Related

Introduction

The following How-To walks you through setting up Virtuoso RDF Graph Replication in a Star Topology.

Prerequisites

Database INI Parameters

Suppose there are 3 Virtuoso instances respectively with the following ini parameters values:

virtuoso1.ini:


...
[Database]
DatabaseFile    = virtuoso1.db
TransactionFile = virtuoso1.trx
ErrorLogFile     = virtuoso1.log
...
[Parameters]
ServerPort               = 1111
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8891
...
[URIQA]
DefaultHost = localhost:8891
...
[Replication]
ServerName   = db1
...

virtuoso2.ini:


...
[Database]
DatabaseFile    = virtuoso2.db
TransactionFile = virtuoso2.trx
ErrorLogFile     = virtuoso2.log
...
[Parameters]
ServerPort               = 1112
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8892
...
[URIQA]
DefaultHost = localhost:8892
...
[Replication]
ServerName   = db2
...

virtuoso3.ini:


...
[Database]
DatabaseFile    = virtuoso3.db
TransactionFile = virtuoso3.trx
ErrorLogFile     = virtuoso3.log
...
[Parameters]
ServerPort               = 1113
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8893
...
[URIQA]
DefaultHost = localhost:8893
...
[Replication]
ServerName   = db3
...

Database DSNs

Use the ODBC Administrator on your Virtuoso host (e.g., on Windows, Start menu -> Control Panel -> Administrative Tools -> Data Sources (ODBC); on Mac OS X, /Applications/Utilities/OpenLink ODBC Administrator.app) to create a System DSN for each of db1, db2, db3, with names db1, db2 and db3, respectively.

Install Conductor package

On each of the 3 Virtuoso instances install the conductor_dav.vad package.

Create a Publication on the Host Virtuoso Instance -- db1

Go to Conductor -> Replication -> Transactional -> Publications:
Click Enable RDF Publishing.
A publication with the name RDF Publication should be created:
Click the link which is the publication name.
You will be shown the publication items page:
Enter for Graph IRI
```
http://example.org
```
Click Add New.
The item will be created and shown in the list of items for the currently viewed publication.

Insert Data into a Named Graph on the Host Virtuoso Instance

There are several ways to insert data into a Virtuoso Named Graph. In this Guide, we will use the Virtuoso Conductor's Import RDF feature:

In the Virtuoso Conductor, go to Linked Data -> Quad Store Upload:
In the presented form:
- Tick the box for Resource URL and enter your resource URL, for e.g.:
```
http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this
```
- Enter for Named Graph IRI:
```
http://example.org
```
Click Upload
A successful upload will result in this message:
Check the inserted triples by executing a query like the following against the SPARQL endpoint, http://cname:port/sparql --
```
SELECT * 
  FROM <http://example.org>
 WHERE { ?s ?p ?o }
```

See how many triples have been inserted in your graph:


SELECT COUNT(*) 
  FROM <http://example.org>
 WHERE { ?s ?p ?o }

Subscribe to the Publication on the a Destination Virtuoso Instance -- db2, db3, etc.

Go to Conductor -> Replication -> Transactional -> Subscriptions:
Click New Subscription:
Specify a new Data Source Enter or selected target data source from the available connected Data Sources:
Click Publications list:
Select the RDF Publication and click List Items:
Click Subscribe.
The subscription will be created:
Click Sync.
Check the retrieved triples by executing the following query:
```
SELECT * 
  FROM <http://example.org>
 WHERE {?s ?p ?o}
```
See how many triples have been inserted into your graph by executing the following query:
```
SELECT COUNT(*) 
  FROM <http://example.org>
 WHERE {?s ?p ?o}
```

These steps may be repeated for any number of Subscribers.

Insert Triples into the Host Virtuoso Instance Graph and check availability at Destination Virtuoso Instance Graph

To check the starting count, on the Destination Virtuoso Instance SPARQL Endpoint, execute:
```
SELECT COUNT(*) 
  FROM <http://example.org>
 WHERE { ?s ?p ?o }
```

On the Host Virtuoso Instance go to Conductor -> Database -> Interactive SQL and execute the following statement:


SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
     <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>
     <http://xmlns.com/foaf/0.1/interest>
     <http://dbpedia.org/resource/Web_Services> 
  } ;
SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
    <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>  	
    <http://xmlns.com/foaf/0.1/interest>  	
    <http://dbpedia.org/resource/Web_Clients> 
  } ;
SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
    <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>  	
    <http://xmlns.com/foaf/0.1/interest>  	
    <http://dbpedia.org/resource/SPARQL> 
  } ;

To confirm that the triple count has increased by the number of inserted triples, execute the following on the Destination Virtuoso Instance SPARQL Endpoint:
```
SELECT COUNT(*) 
  FROM <http://example.org>
 WHERE { ?s ?p ?o }
```