16.19.2. Replication Topologies

Typical replication topologies are Chains, Stars and Bi-directional. They can be achieved with Virtuoso, by repeating the "Publish" and/or "Subscribe" steps on each relevant node.

Star Replication Topology

In a Star, there is one Publisher, and many Subscribers.

Figure 16.202. Star Replication Topology

To set up a Star, follow the scenario:

Configure Instance #1 to Publish.
Configure Instance #2 to Subscribe to #1.
Repeat as necessary.

Star Replication Topology Example

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 = example.com: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 = example.com: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

Figure 16.203. Star Replication Topology
Click Enable RDF Publishing
A publication with the name RDF Publication should be created:

Figure 16.204. Star Replication Topology
Click the link which is the publication name.
You will be shown the publication items page:

Figure 16.205. Star Replication Topology
Enter for Graph IRI:
```
http://example.org
```
Figure 16.206. Star Replication Topology
Click Add New
The item will be created and shown in the list of items for the currently viewed publication.

Figure 16.207. Star Replication Topology

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 example, we will use the Virtuoso Conductor's Import RDF feature:

In the Virtuoso Conductor, go to Linked Data -> Quad Store Upload:

Figure 16.208. Replication Topology
In the 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
```
Figure 16.209. Replication Topology
Click Upload
A successful upload will result in this message:

Figure 16.210. Star Replication Topology
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 }
```
Figure 16.211. Star Replication Topology
See how many triples have been inserted in your graph:
```
SELECT COUNT(*)
  FROM <http://example.org>
 WHERE { ?s ?p ?o }
```
Figure 16.212. Star Replication Topology

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

Go to Conductor -> Replication -> Transactional -> Subscriptions

Figure 16.213. Star Replication Topology
Click New Subscription

Figure 16.214. Star Replication Topology
Specify a new Data Source Enter or selected target data source from the available connected Data Sources:

Figure 16.215. Star Replication Topology

Figure 16.216. Star Replication Topology
Click Publications list

Figure 16.217. Star Replication Topology
Select the RDF Publication and click List Items

Figure 16.218. Star Replication Topology
Click Subscribe
The subscription will be created

Figure 16.219. Star Replication Topology
Click Sync
Check the retrieved triples by executing the following query
```
SELECT *
  FROM <http://example.org>
 WHERE {?s ?p ?o}
```
Figure 16.220. Star Replication Topology
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}
```
Figure 16.221. Star Replication Topology

These steps may be repeated for any number of Subscriber.

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>
  } ;

Figure 16.222. Star Replication Topology

Figure 16.223. Star Replication Topology

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 }
```
Figure 16.224. Star Replication Topology

Chain Replication Topology

In a Chain, there is one original Publisher, to which there is only one Subscriber. That Subscriber may also serve as a Publisher, again with only one Subscriber. The chain ends with a Subscriber which does not Publish.

Figure 16.225. Chain Replication Topology

To set up a Chain, follow the scenario:

Configure Instance #1 to Publish.
Configure Instance #2 to Subscribe to #1.
Configure Instance #2 to Publish.
Configure Instance #3 to Subscribe to #2.
Repeat as necessary.

Chain Replication Topology Example

The following How-To walks you through setting up Virtuoso RDF Graph Replication in a Chain 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 = example.com: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 = example.com:8893
...
[Replication]
ServerName   = db3
...

Database DSNs

Install Conductor package

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

Create Publication on db1

Go to http://example.com:8891/conductor and log in as dba
Go to Conductor - > Replication - > Transactional - > Publications

Figure 16.226. Chain Replication Topology
Click

Enable RDF Publishing
As result publication with the name

RDF Publication

should be created

Figure 16.227. Chain Replication Topology
Click the link which is the publication name.
You will be shown the publication items page

Figure 16.228. Chain Replication Topology
Enter for Graph IRI:
```
http://example.org
```
Figure 16.229. Chain Replication Topology
Click Add New
The item will be created and shown in the list of items for the currently viewed publication.

Figure 16.230. Chain Replication Topology

Create subscription from db2 to db1's Publication

Log in at http://example.com:8892/conductor
Go to Replication - > Transactional - > Subscriptions

Figure 16.231. Chain Replication Topology
Click

New Subscription

Figure 16.232. Chain Replication Topology
From the list of "Specify new data source" select Data Source db1

Figure 16.233. Chain Replication Topology
Enter for db1 dba user credentials

Figure 16.234. Chain Replication Topology
Click "Add Data Source"
As result

db1

will be shown in the "Connected Data Sources" list.

Figure 16.235. Chain Replication Topology
Select

db1

the "Connected Data Sources" list and click "Publications list"

Figure 16.236. Chain Replication Topology
As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".

Figure 16.237. Chain Replication Topology
As result will be shown the "Confirm subscription" page.

Figure 16.238. Chain Replication Topology
The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.

Figure 16.239. Chain Replication Topology
Click "Subscribe"
The subscription will be created.

Figure 16.240. Chain Replication Topology

Create Publication on db2

Go to http://example.com:8892/conductor and log in as dba
Go to Conductor - > Replication - > Transactional - > Publications

Figure 16.241. Chain Replication Topology
Click

Enable RDF Publishing
As result publication with the name

RDF Publication

should be created

Figure 16.242. Chain Replication Topology
Click the link which is the publication name.
You will be shown the publication items page

Figure 16.243. Chain Replication Topology
Enter for Graph IRI:
```
http://example.org
```
Figure 16.244. Chain Replication Topology
Click Add New
The item will be created and shown in the list of items for the currently viewed publication.

Figure 16.245. Chain Replication Topology

Create subscription from db3 to db2's Publication

Log in at http://example.com:8893/conductor
Go to Replication - > Transactional - > Subscriptions

Figure 16.246. Chain Replication Topology
Click

New Subscription

Figure 16.247. Chain Replication Topology
From the list of "Specify new data source" select Data Source db2

Figure 16.248. Chain Replication Topology
Enter for db2 dba user credentials

Figure 16.249. Chain Replication Topology
Click "Add Data Source"

Figure 16.250. Chain Replication Topology
As result

db2

will be shown in the "Connected Data Sources" list. Select it and click "Publications list"

Figure 16.251. Chain Replication Topology
As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".

Figure 16.252. Chain Replication Topology
As result will be shown the "Confirm subscription" page.

Figure 16.253. Chain Replication Topology
The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.

Figure 16.254. Chain Replication Topology
Click "Subscribe"
The subscription will be created.

Figure 16.255. Chain Replication Topology

Insert Data into a Named Graph on the db1 Virtuoso Instance

Log in at http://example.com:8891/conductor
Go to Linked Data -> Quad Store Upload:

Figure 16.256. Chain Replication Topology
In the shown form:
1. Tick the box for
  
  Resource URL
  
  and enter your resource URL, e.g.:
```
http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this
```
2. Enter for Named Graph IRI:
```
http://example.org
```
  Figure 16.257. Chain Replication Topology
Click Upload
A successful upload will result in a shown message.

Figure 16.258. Chain Replication Topology
Check the count of the inserted triples by executing a query like the following against the SPARQL endpoint, http://example.com:8891/sparql:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Figure 16.259. Chain Replication Topology
Should return

57

as total.

Figure 16.260. Chain Replication Topology

Check data on the Destination instances db2 and db3

To check the starting count, on each of the Destination Virtuoso Instances db2 and db3 from SPARQL Endpoint execute:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

57

as total.

Figure 16.261. Chain Replication Topology

Add new data on db1

Disconnect db2 and db3.

On the Host Virtuoso Instance db1 go to Conductor - > Database - > Interactive SQL enter 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>
  } ;

Figure 16.262. Chain Replication Topology

Click "Execute"
As result the triples will be inserted

Figure 16.263. Chain Replication Topology
Check the count of the destination instance graph's triples by executing the following query like against the SPARQL endpoint, http://example.com:8891/sparql:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

60

as total.

Figure 16.264. Chain Replication Topology

Check data on the Destination instances db2 and db3

Start instances db2 and db3
To confirm that the triple count has increased by the number of inserted triples, execute the following on the Destination Virtuoso Instance db2 and db3 SPARQL Endpoint:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

60

as total.

Figure 16.265. Chain Replication Topology

Bi-directional Replication Topology

Bi-directional Replication Topology Example

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

db1 <---- db2
db1 ---->

 db2

Prerequisites

Database INI Parameters

Suppose there are 2 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 = example.com: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
...

Database DSNs

Install Conductor package

On each of the 2 Virtuoso instances install the conductor_dav.vad package.

Create Publication on db2

Go to http://example.com:8892/conductor and log in as dba
Go to Conductor -> Replication -> Transactional -> Publications

Figure 16.266. Bi-directional Replication Topology
Click

Enable RDF Publishing
As result publication with the name

RDF Publication

should be created

Figure 16.267. Bi-directional Replication Topology
Click the link which is the publication name.
You will be shown the publication items page

Figure 16.268. Bi-directional Replication Topology
Enter for Graph IRI:
```
http://example.org
```
Figure 16.269. Bi-directional Replication Topology
Click Add New
The item will be created and shown in the list of items for the currently viewed publication.

Figure 16.270. Bi-directional Replication Topology

Create subscription from db1 to db2's Publication

Log in at http://example.com:8891/conductor
Go to Replication -> Transactional -> Subscriptions

Figure 16.271. Bi-directional Replication Topology
Click

New Subscription

Figure 16.272. Bi-directional Replication Topology
From the list of "Specify new data source" select Data Source db2

Figure 16.273. Bi-directional Replication Topology
Enter for db2 dba user credentials

Figure 16.274. Bi-directional Replication Topology
Click "Add Data Source"
As result

db2

will be shown in the "Connected Data Sources" list.

Figure 16.275. Bi-directional Replication Topology
Select

db2

the "Connected Data Sources" list and click "Publications list"

Figure 16.276. Bi-directional Replication Topology
As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".

Figure 16.277. Bi-directional Replication Topology
As result will be shown the "Confirm subscription" page.

Figure 16.278. Bi-directional Replication Topology
The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.

Figure 16.279. Bi-directional Replication Topology
Click "Subscribe"
The subscription will be created.

Figure 16.280. Bi-directional Replication Topology

Create Publication on db1

Go to http://example.com:8891/conductor and log in as dba
Go to Conductor -> Replication -> Transactional -> Publications

Figure 16.281. Bi-directional Replication Topology
Click

Enable RDF Publishing
As result publication with the name

RDF Publication

should be created

Figure 16.282. Bi-directional Replication Topology
Click the link which is the publication name.
You will be shown the publication items page

Figure 16.283. Bi-directional Replication Topology
Enter for Graph IRI:
```
http://example.org
```
Figure 16.284. Bi-directional Replication Topology
Click Add New
The item will be created and shown in the list of items for the currently viewed publication.

Figure 16.285. Bi-directional Replication Topology

Create subscription from db2 to db1's Publication

Log in at http://example.com:8892/conductor
Go to Replication -> Transactional -> Subscriptions

Figure 16.286. Bi-directional Replication Topology
Click

New Subscription

Figure 16.287. Bi-directional Replication Topology
From the list of "Specify new data source" select Data Source db1

Figure 16.288. Bi-directional Replication Topology
Enter for db1 dba user credentials

Figure 16.289. Bi-directional Replication Topology
Click "Add Data Source"

Figure 16.290. Bi-directional Replication Topology
As result

db1

will be shown in the "Connected Data Sources" list. Select it and click "Publications list"

Figure 16.291. Bi-directional Replication Topology
As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".

Figure 16.292. Bi-directional Replication Topology
As result will be shown the "Confirm subscription" page.

Figure 16.293. Bi-directional Replication Topology
The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.

Figure 16.294. Bi-directional Replication Topology
Click "Subscribe"
The subscription will be created.

Figure 16.295. Bi-directional Replication Topology

Insert Data into a Named Graph on the db2 Virtuoso Instance

Log in at http://example.com:8892/conductor
Go to Linked Data -> Quad Store Upload:

Figure 16.296. Bi-directional Replication Topology
In the shown form:

Tick the box for

Resource URL

and enter your resource URL, e.g.:

http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this

Enter for Named Graph IRI:
```
http://example.org
```
Figure 16.297. Bi-directional Replication Topology
Click Upload
A successful upload will result in a shown message.

Figure 16.298. Bi-directional Replication Topology
Check the count of the inserted triples by executing a query like the following against the SPARQL endpoint, http://example.com:8892/sparql:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Figure 16.299. Bi-directional Replication Topology
Should return

57

as total.

Figure 16.300. Bi-directional Replication Topology

Check data on the Destination instance db1

To check the starting count, execute from db1's SPARQL Endpoint:

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

Should return

57

as total.

Figure 16.301. Bi-directional Replication Topology

Add new data on db2

Disconnect db1.

On the Host Virtuoso Instance db2 go to Conductor -> Database -> Interactive SQL enter 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>
  } ;

Figure 16.302. Bi-directional Replication Topology

Click "Execute"
As result the triples will be inserted

Figure 16.303. Bi-directional Replication Topology
Check the count of the destination instance graph's triples by executing the following query like against the SPARQL endpoint, http://example.com:8892/sparql:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

58

as total.

Figure 16.304. Bi-directional Replication Topology

Check data on the Destination instance db1

Start instance db1
To confirm that the triple count has increased by the number of inserted triples, execute the following statement on db1's SPARQL Endpoint:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

58

as total.

Figure 16.305. Bi-directional Replication Topology

Add new data on db1

Disconnect db2.

On the Host Virtuoso Instance db1 go to Conductor -> Database -> Interactive SQL enter 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_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>
  } ;

Figure 16.306. Bi-directional Replication Topology

Click "Execute"
As result the triples will be inserted

Figure 16.307. Bi-directional Replication Topology
Check the count of the destination instance graph's triples by executing the following query like against the SPARQL endpoint, http://example.com:8891/sparql:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

60

as total.

Figure 16.308. Bi-directional Replication Topology

Check data on the Destination instance db2

Start instance db2
To confirm that the triple count has increased by the number of inserted triples, execute the following statement on db2's SPARQL Endpoint:
```
SELECT COUNT(*)
   FROM <http://example.org>
WHERE { ?s ?p ?o }
```
Should return

60

as total.

Figure 16.309. Bi-directional Replication Topology

Prev	Up	Next
16.19. RDF Graph Replication	Home	16.19.3. Set up RDF Replication via procedure calls

Prefix	IRI
schema	http://schema.org/
n5	http://creativecommons.org/licenses/by/4.0/
rdf	http://www.w3.org/1999/02/22-rdf-syntax-ns#
n4	http://www.openlinksw.com/#
n2	http://docs.openlinksw.com/virtuoso/rdfgraphreplicationtopl/
xsdh	http://www.w3.org/2001/XMLSchema#

Prefix	URI
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xmlns:n5	http://creativecommons.org/licenses/by/4.0/
xmlns:rdf	http://www.w3.org/1999/02/22-rdf-syntax-ns#
xmlns:n4	http://www.openlinksw.com/#
xmlns:n2	http://docs.openlinksw.com/virtuoso/rdfgraphreplicationtopl/
xmlns:xsdh	http://www.w3.org/2001/XMLSchema#

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n2:	schema:datePublished	2016-09-09 16:16:54
n2:	schema:headline	16.19.2.ÃÂ Replication Topologies
n2:	schema:keywords	OpenLink,Virtuoso,database,RDBMS,relational,SQL,RDF,triple store,linked data,linked open data,Big Data,ODBC,SPARQL
n2:	schema:license	n5:deed.en_US
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n2:	schema:url	n2:
_:vb81273	rdf:type	schema:Organization
_:vb81273	schema:name	OpenLink Software
_:vb81273	schema:url	n4:this
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_:vb81274	schema:url	n4:this