OpenCities Map provides the ability to store feature attributes in a relational database. This is done by associating (or linking) a row in a relational database to an element in the design and storing information about the linkage in the DGN file. To link a table to a graphical element, the table must have a numeric MSLINK column. This column acts as a unique row identifier (essentially a row ID) for OpenCities Map.

The second requirement is that the database must contain a table called MSCATALOG. The attribute table name is entered into MSCATALOG and assigned a unique entity number.

There are two pieces of information that are used to retrieve the correct row from the correct table. The first is the entity number, which is a unique value assigned to the table in the MSCATALOG. The second is the MSLINK number, which is a unique value assigned to the row of data in the attribute table. When a database row is linked to a graphical element, attribute data, in the form of a USER DATA Linkage containing the MSLINK and entity number, is written to the element.

Once this linkage is established you can manipulate and review the database information from inside OpenCities Map.

OpenCities Map supports database supports a direct connection to Oracle databases. In addition, database connectivity through industry standards ODBC and OLE DB is also supported.

The database is specified in the Database node of a geospatial project which is created and edited with the OpenCities Geospatial Administrator.

In OpenCities Map, the Features ribbon group from Map Database Linkages workflow, provides convenient access to the following database tools.

Name	Icon	Description
Length Update		Changes the database values for line lengths.
Coordinate Update		Changes the database values for endpoint, range or origin coordinates.
Area/Perimeter Update		Computes area and perimeter values.
Text Manager Update		Relates text in the design file to database attributes.