Using ARC's RDF Store

Setup

An ARC Store is instantiated like any other component:

/* ARC2 static class inclusion */ 
include_once('path/to/arc/ARC2.php');

/* configuration */ 
$config = array(
  /* db */
  'db_host' => 'localhost', /* optional, default is localhost */
  'db_name' => 'my_db',
  'db_user' => 'user',
  'db_pwd' => 'secret',

  /* store name (= table prefix) */
  'store_name' => 'my_store',
);

/* instantiation */
$store = ARC2::getStore($config);

Creating the MySQL tables

if (!$store->isSetUp()) {
  $store->setUp();
}

Running Queries

$q = 'SELECT ...';
$rs = $store->query($q);
if (!$store->getErrors()) {
  $rows = $rs['result']['rows'];
  ...
}

ARC supports standard SPARQL queries as well as SPARQL+ for write operations.

Result formats

The default query() method returns an associative array with two keys: "query_time" and "result". The former tells how long the SPARQL engine needed to process the query (excluding parse time), the latter contains query-dependent sub-structures. The query() method also accepts a second parameter to specify a result format. Examples are listed below:

query('SELECT ?fname ...')

$duration = $rs['query_time'];
$rows = $rs['result']['rows'];
$row = $rows[0];
$val = $row['fname'];

query('SELECT ?fname ...', 'rows')
```
$rows = $rs;
...
```
query('SELECT ?fname ...', 'row')
```
$row = $rs;
...
```

query('ASK ...')

$duration = $rs['query_time'];
$true_or_false = $rs['result'];

query('ASK ...', 'raw')
```
$true_or_false = $rs;
```
query('DESCRIBE <http://example.com/>...')
```
$duration = $rs['query_time'];
$index = $rs['result'];
$res = $index['http://example.com/'];
```
The index format is described in Internal Structures.
query('DESCRIBE <http://example.com/>...', 'raw')
```
$index = $rs;
...
```
query('CONSTRUCT ...') works analogue to DESCRIBE

query('LOAD ...')

$duration = $rs['query_time'];
$added_triples = $rs['result']['t_count'];
$load_time = $rs['result']['load_time'];
$index_update_time = $rs['result']['index_update_time'];

query('LOAD ...', 'raw')

$added_triples = $rs['t_count'];
$load_time = $rs['load_time'];
$index_update_time = $rs['index_update_time'];

query('INSERT ...') works analogue to LOAD

query('DELETE ...')

$duration = $rs['query_time'];
$removed_triples = $rs['result']['t_count'];
$delete_time = $rs['result']['delete_time'];
$index_update_time = $rs['result']['index_update_time'];

query('DELETE ...', 'raw')

$removed_triples = $rs['t_count'];
$delete_time = $rs['delete_time'];
$index_update_time = $rs['index_update_time'];

query('DUMP) creates (and outputs) a store backup (see dump method below), the result format parameter has no effect

Advanced query parameters

Besides a query and result_format, the query() method accepts two other parameters: query_base and whether to keep_bnode_ids.

"query_base" (parameter #3, default: empty) allows you to specify a base for the query (e.g. if the query contains relative paths, but no BASE).
"keep_bnode_ids" (parameter #4, default: false) is an advanced trigger that enables deletes and updates of blank nodes. ARC supports bnode identification for read operations, i.e. bnode IDs returned by a SELECT can be used in successive queries, if masked as URIs (e.g. <_:bn27>). Likewise, ARC can be told to write bnodes to the store without changing their IDs:
```
$q1 = 'DELETE FROM <...> { <_:methuselah> ex:age ?age . }';
$q2 = 'INSERT INTO <...> { <_:methuselah> ex:age 969 . }';
$store->query($q1, 'raw', '', true);
$store->query($q2, 'raw', '', true);
```

Other methods

reset()
All tables are emptied.
drop()
All tables are deleted.
insert($doc, $g, $keep_bnode_ids = 0)
A convenience method. $doc can be an ARC structure, or an ARC-supported RDF format (including HTML), $g is the target graph URI, $keep_bnode_ids is explained in the paragraph above.
dump()
Creates a SPOG document from all quads in the store. This method can be used for streamed store backups.
createBackup($path, $q = '')
Saves a SPOG file that either contains a complete store dump, or triples/quads from a custom, SPO(G)-compliant SELECT query (via the $q parameter).
replicateTo($name)
Creates a new store and replicates all tables and quads to it.
renameTo($name)
Renames the store's underlying database tables.
optimizeTables($level = 2) /* 1: triple + g2t, 2: triple + *2val, 3: all tables */
Defragments the MySQL tables. This method is automatically called every ~50th LOAD or DELETE query. You can also call it explicitly, though, when queries are getting slower than they should due to store updates.

Querying remote SPARQL endpoints

ARC provides a dedicated "RemoteStore" component for running queries against Web-accessible SPARQL endpoints.