===== Dataset Structure - Rules =====

{{  datasetstructure_rules.png?nolink|}}

This page describes the Dataset Structure - Rules panel.

{{orbitgis:how_to_find.png?25&nolink |}} [[191:desktop:dataset:properties|Dataset Properties]] > [[191:desktop:dataset:contents:index|Structure]] > Rules

===== Concepts =====

An attribute value can be calculated automatically or constrained via a value-list by using an "Attribute Rule".
Rules are stored in the [[191:technology:supported_formats:other:ord|Orbit Resource Descriptor]] file and  apply to a single attribute. 

===== Attribute Rules =====

**None** \\
Default, no attribute rule applied. 

**Formula** \\
The attribute value will be derived from the object's spatial component or calculated using other attribute values of the same attribute set. \\
All available attribute formulas are listed here : [[191:desktop:dataset:contents:formulas|]].

**Valuelist** \\
The attribute value will be constrained to a list of predefined values. \\
One can enter all value-list values and their corresponding labels one by one or import all values and labels at once. \\
When editing the attribute value in the [[191:desktop:tabs:inspector|Object Inspector]] the value-list drop-down menu will be opened, only one of the predefined values can be selected. 

Import a value-list using a *.txt, *.csv or *.dbf file. The first line will be ignored if headers are "value" and "label". use tab, comma or semicolon as separator. For example : 
<code bash>value;Label
Value1;Label1
Value2;Label2
Value3;Label3
</code>

===== Attribute Set Rules =====

** One set of attribute values required ** \\
Using this option each object will have at least one set of attribute values. \\
According the Orbit vector data structure concepts, an object can have no, one or more sets of attribute values. \\
This option will create and add automatically one set of attribute values for each object. More sets of attribute values can be added at all time.