Mulgara

== System Graphs and Server URIs ==

Mulgara maintains a ''system graph'', which is akin to the system tables of a traditional Relational Database system.

The URI of the system graph is generated from the ''server URI''.  The server URI is meant to uniquely identify a server and, in the case of a standalone RMI server, describe the location used for querying the server from an RMI client.  It is constructed in the following manner:

{{{

rmi://<hostname>[:rmiport]/<servername>

}}}

where <hostname> is the canonical network name for the host (the result from the 'hostname' command in Linux); [:rmiport] is the optional port number for the RMI registry, specified only if it's running on a different port from the default 1089; and <servername> is the name of the server (you can have multiple servers deployed on the same host; defaults to "server1").  All of these parameters may be changed in the configuration.

'''NOTE:'''  The server URI is ''not'' the same as the server ''address''.  In other words, "server URI" is a bit of a misnomer.  It is an internal label Mulgara constructs and maintains; it only works as a network address for {{{rmi:}}} clients, not SPARQL over HTTP clients, etc.  But it non-{{{rmi:}}} clients can nevertheless use it as (part of) a Graph URI.

The ''system graph URI'' is defined relative to the server URI, and is constructed by simply appending an empty fragment - {{{#}}} - to the server URI.  For a standalone Mulgara server running a default configuration, you can use {{{<rmi://localhost/server1#>}}} to refer to the system graph because Mulgara will resolve aliases to the local host when it evaluates RMI graph URIs.

To dump the sysgraph of the default server try executing the following SPARQL query as the Query Text in the sample WebUI interface (don't forget the angle brackets):

{{{

select ?x ?y ?z from <rmi://localhost/server1#> where {?x ?y ?z}

}}}