The ConceptBase Server

 

The ConceptBase server offers TCP/IP access to the functionality of the O-Telos languages. Specifically, it allows to TELL, UNTELL O-Telos objects and to ASK O-Telos object bases. The operations are called by clients ( for example the user interfaces described in section 4). An arbitrary number of clients can connect to a single ConceptBase server.

The ConceptBase server is started by a command line

  $CB_HOME/bin/CBserver <params>

The following parameters are available:

-d db

Set database db to be loaded. If the database does not exist it is created and initialized with the O-Telos pre-defined objects. A database is maintained as a Unix directory. The parameter is mandatory except when the update mode is set to nonpersistent (see below).

-u updatemode

controls update persistency The value updatemode is either persistent or nonpersistent. In non-persistent mode, all updates are lost after the ConceptBase server is stopped. In persistent mode, updates are stored in the database and will be available for future sessions.

-p portnr

sets the TCP/IP socket portnumber for client connections to the ConceptBase server. The value portnr must be between 2000 and 99999. If there is already a process using the portnumber, the ConceptBase server will abort. The default value for the portnumber is 4001.

-t tracemode

sets the tracemode of the ConceptBase server. It is one of no,low,high,veryhigh. The tracemode determines the amount of text displayed by the server during its execution. The tracemode does not influence the function but is used for debugging.

-t queryrep

sets the default internal representation for rules and queries. The value queryrep is one of MagicSet, SLDNF. The Magic set representation allows bottom-up query evaluation, the SLDNF realizes a top-down strategy. Default (and recommended) is SLDNF.

-c cachemode

turns on the query cache to allow recursive query evaluation. The value cachemode is one of off, transient (default). This parameter is controlling the SLDNF evaluation strategy.

-o optmode

controls the optimizer for rules, constraints and queries. The value optmode is one of 0 (no optimization), 1 (structural optimization by exploiting builtin O-Telos axioms), 2 (optimizing join order) or 3 (combines 1 and 2). Default and recommended is 3.

-r secs

automatically restarts the server after a crash. The value secs specifies how many seconds to wait before restart. Crashes are infrequent with the ConceptBase server. Use this option only when you want maximum accessibility of the server.

The trace of the ConceptBase server can be saved by redirecting its output, e.g.

$CB_HOME/bin/CBserver -r 10 -p 4444 -t high -d MYDB >> mylogfile.log

The ConceptBase server requires Sun Solaris 2.4 or higher as operating system. Versions for other operating systems are currently not available.