====== Spatial Objects ======

===== The Spatial Information Object - SIO =====

In Orbit Technology, every single entity of spatial data is considered to be a Spatial Information Object or **SIO**. A single object contains the data referring to a single feature in reality.

In Orbit, all SIO's belong to exactly one Model. Its internal structure complies with the Model definition.

The SIO contains three major components : **Spatial Component**, **Attribute Component**, **Reference Component**. These components build up the data. \\  Additionally, a **Layout Component** can be defined adding an object-specific non-spatial graphic representation.

===== The Spatial Component - SC =====

This component holds the spatial details of the SIO : a list of co-ordinates, or an image. The contents comply with the model definition SC type : Point, Line, Area or Image.

Pointlists can be extended with a range of flags that indicate overlays, donut-shapes etc.

The SC is an obliged component.

===== The Attribute Component - AC =====

This components holds the descriptive data in tabular form. The AC consists out of one or more **Attribute Sets **(or Attribute Tables) which is the equivalent of a table definition : a range of fields with their datatype definition.

For each Attribute Set, the AC can hold one or more data rows. Each row contains a value for each field in the Attribute Set.

The AC is an obliged component.

===== The Reference Component - RC =====

This component holds references of this SIO to other SIO's, and registers the nature of that relationship. For example, an SIO or type Area can refer to a range of SIO's type Line with nature 'Structural Area' : the Area is then constructed out of the lines of the references SIO's. In such case, the Area's SC can be exceptionally empty.

The RC is optional.

===== The Layout Component - LC =====

This component holds an SIO-specific layout definition, such as the display of an attribute field as text item on a map, or the display of a pie chart based on several attribute fields. Layout Components define a non-spatial display of the SIO. The text display or pie chart display are defined by a Layout Style which is a definition known within the Model.

The LC is optional.