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Feature Database (FDB) files

What is a Feature Database (FDB) File

Creating an FDB

Opening an FDB

Constructing graphics on an FDB overlay

Saving data in an FDB file

Compacting an FDB file

Feature Database (FDB) files versus Base Dataset (BDS) files

What is a Feature Database (FDB) File

The Cadcorp Feature Database (FDB) cursor-based dataset is a file based database encapsulated in a single file, designed to store up to one terabyte (TB) of simple geometry type data. FBD files are of benefit to users who want to store medium to large volumes of geographic data without having to invest in database server technology and management resources, and for remote or mobile users. Unlike Access based equivalents, an FDB file supports multi-user, multi-edit operations.

The FDB is a cursor based dataset. This means that it only supports OGC Simple Features entities, specifically Points, LineString and Polygon items.

The FDB is not a replacement for (GB specific), it is an alternative. Please bear the following in mind when considering the best format to use:

FDB format allows a number of different users to edit the same dataset.
FDB supports feature level locking.
FDB files do not support topology.
FDB files only support Points, LineString and Polygon items in terms of geometry. They do not support true arcs, circles or Beziers (these features are facetted). Only Point Text items are supported.
FDB files have homogeneous attributes, this means each item in an FDB will always have the same set of attributes, it doesn't matter if some of the schema attributes remain empty, but every feature will have the same structured schema; BDS files have heterogeneous attributes, this means you can have the same schema items on all features and you can add extra attributes to individual features, this cannot be done with FDB files (hence the New user attribute radio button on the FDB Schema - Add Property Column... > Pick Property dialog is unavailable).

FDB replaces the SDS native geometry format used in some earlier versions of Cadcorp SIS. SDS files cannot be created in SIS, although they can be opened, edited and saved.

Creating an FDB

See the Cadcorp Feature Database (*.fdb) section of Create new file.

Opening an FDB

To open an existing FDB file, select Add Overlay [Home-Map] to display the Overlay Types dialog and select File from the Files tab. In the File Browser dialog navigate to the required folder, choose Cadcorp Feature Database (*.fdb) from the Files of type drop down box, select the required file and click Finish.

Note: FDB files created in Cadcorp SIS V6 are opened as read-only.

Constructing graphics on an FDB overlay

As you construct graphical items, they are placed on the current overlay. To make the FDB current use its local Make Current command in the Maps Control Bar).

The FDB status must also be set to Editable, this can be done either in the Overlays dialog, or from the Status local command in the Maps Control Bar.

Saving data in an FDB file

As soon as you create the FDB file as described above, it exists in the location where you created it. However, the graphics you construct on this FDB are not saved until you save the SWD using one of the following options:

Save [File-Save]

Save All [File-Save]

Save As [File-Save As]

Save Copy As [File-Save As]

Compacting an FDB file

Deleting data from an FDB file does not reduce its size. It is therefore useful to compact the file to reduce its size. This can be achieved with the CompactDataset Method in the Programming Help.

Feature Database (FDB) files versus Base Dataset (BDS) files

FDB and BDS files are both standard Cadcorp formats. The choice of file formats depends on their use, the details of each file type are summarized in the following table.

	Base Dataset (BDS)	Feature Database (FDB)
Geometry	Stores complex vector, topological geometry and raster images.	Well-known-binary format used for geometry. i.e. compatible with OpenGIS Simple Features Specification. No topology, no cartographic text (use Point item with text attribute and create a Label theme) and no true arcs, circles (faceted) or Beziers, i.e. supports only straight geometry.
Capacity	Limited	1 Terabyte
Read as	Memory	Cursor
Considerations	Dates held formatted, (i.e. 12/6/2009) Boolean held formatted, (i.e. True/False), but displayed in table window -1=True, 0=False	Dates held in Julian format, (i.e. 41255). Boolean held and displayed as -1=True, 0=False. Uses Database Query Wizard
Advantages	Items can each have different attributes. Item styles stored. Complex geometry stored.	Items all have the same attributes. Multi-user editable with feature level locking.
Disadvantages	Can be multi-user Hittable, not multi-user Editable.	No storage of Item styles. Simple geometry only stored.

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