Feature Representation

In addition to the generic FME feature attributes that FME Workbench adds to all features, this format adds the format-specific attributes described in this section.

The OGDI feature attributes consist of the columns that were in the Microsoft Windows Azure Table. All OGDI features contain an ogdi_type attribute, which is set to ogdi_<geometry type> for any supported geometry.

The OGDI format uses KML snippets to keep the geometry in the Windows Azure Table.

The following table summarizes the attribute types supported:

Parameter

Contents

text Text attributes store variable length strings. This type is also used to store date values.
integer Integer attributes store integer numbers in contrast to floating point numbers.
boolean Boolean attributes store true or false values.
number Number attributes store floating point numbers.

The OGDI module makes use of the following special attribute names:

Attribute Name

Contents

ogdi_type

The type of geometric entity stored within the feature. The valid values for the object model are listed below:

ogdi_none

ogdi_point

ogdi_line

ogdi_area

ogdi_aggregate

ogdi_last_update The UTC date and time value formatted as a string representing the time this table was last updated. For example: 2010-10-12 18:23:47.574000
ogdi_partitionkey The unique value for partition that this row will be a part of. Partitioning helps with load balancing on the server when retrieving data. If no value is provided a single GUID will be used for all ll feature written I a given translation for each table. Any text value is permissible.
ogdi_rowkey

Specifies or retrieves a unique identifier per row. If set, this should be unique per input feature. If a value is not provided, a unique GUID will be generated for each row inserted into a given table.

ogdi_kml_name Specifies a name for the geometry stored at each row in the table. This name is written directly into the KML snippet. If a value is not provided, a value of 'None' will be written for the KML geometry name.
ogdi_kml_description Specifies a description for the geometry stored at each row in the table. This description is written directly into the KML snippet. If a value is not provided, a value of 'None' will be written for the KML geometry name.

No Coordinates

ogdi_type: ogdi_none

Features with no coordinates are tagged with this value when reading or writing to or from OGDI. Note also that this is a valid KML snippet but is not particularly significant.

Points

ogdi_type: ogdi_point

Features tagged with this value consist of a single point. Both singular points and aggregates of points are supported. Point aggregates will become aggregates while singular points will become points in OGDI.

Line

ogdi_type: ogdi_lines

Linear features are tagged with this value when reading or writing to or from OGDI. A line consists of one or more ordered two-point line segments. Line aggregates will become aggregates while singular lines will become lines in OGDI.

Area

ogdi_type: ogdi_area

Area or polygon features are tagged with this value when reading or writing to or from OGDI. Both single-part and aggregate area features are supported. A single area feature may be either a polygon or a donut polygon. Area aggregates will become aggregates while singular areas will become polygons in OGDI. Note that NO checking is done to ensure that the area features adhere to the geometry rules of OGDI as they are loaded.

GeometryCollections

ogdi_type: ogdi_aggregate

Aggregates containing either homogeneous or heterogeneous collections of point, line and polygon features are processed through FME as single features when reading to or writing from OGDI.