/*!
\mainpage GRASS 6 DataBase Management Interface

by GRASS Development Team

http://grass.itc.it

\section intro Introduction

The attribute management was completely changed in GRASS 5.7/6 to achieve
multi-attribute capabilities managed within external databases.  The former
dig_cats/ files are not used any more and all vector attributes are stored
in external database. Connection with database is done through DBMI library
(DataBase Management Interface) with its integrated drivers. At time of this
writing following DBMI drivers for attribute storage are available:

<ul>
<li> DBF: xBase files
<li> ODBC: to interface from www.unixodbc.org
<li> PostgreSQL driver (note that PostgreSQL can also be accessed through
     ODBC)
<li> mySQL
</ul>

These drivers are compiled depending on present libraries and 'configure'
settings. Only the DBF driver is always compiled.

In general records in table are linked to vector entities by field number
and category number.  The field number identifies a database table and the
category number identifies the record record. I.e. for unique combination
<tt>mapset + map + field + category</tt> exists one unique combination
<tt>driver + database + table + row</tt>. Each element may have none, one or
more categories (cats). More cats are distinguished by field number (field).
The flexibility of this approach even supports the extreme case, that one
vector entity may be linked to attributes in different tables in different
databases connected by different drivers at the same time.

The DBMI library contains drivers such as DBF, ODBC, and PostgreSQL
(planned). The functionality of the database support varies with the
capabilities of the underlying RDBMS. Main features are multi-attributes
support for various data types, also multiple tables may optionally be
linked to one or many vector entity/ies. SQL (Structured Query Language) is
used for all drivers.



For DBMI architecture details please read Blazek et al. 2002 (see below).


\section contacts Contacts

 Radim Blazek <blazek@itc.it>


\section references References

Text based on: R. Blazek, M. Neteler, and R. Micarelli. The new GRASS 5.1
 vector architecture. In Open source GIS - GRASS users conference 2002,
 Trento, Italy, 11-13 September 2002. University of Trento, Italy, 2002.
 http://www.ing.unitn.it/~grass/proceedings/proceedings/pdfs/Blazek_Radim.pdf

\section seealso See Also
 
<a href="../../vector/html/index.html">Vector Architecture</a>

Last change: $Date: 2005/01/12 15:53:59 $
*/
