Before Chris and I start to dive in and explain how DIGGS fits together I thought it would be useful to clarify the terms that we are going to use when describing the structure of DIGGS. So here goes ....

Everything in a DIGGS file is an object, a property, a value or an attribute. Objects contain properties, and properties have values and attributes. Example 1 illustrates these simple relationships.

<Object>
	<property1 attribute=””>value</property1>
	<property2 attribute=””>value</property2>
</Object>

Objects can only contain properties and cannot directly contain other objects. This rule results in the Example 2 being invalid as Object1 directly contains Object2.

<Object1>
	<property1>Value</property1>
	<property2>Value</property2>
  	<Object2>
	  	 <property1>Value</property1>
 	 </Object2>
</Object1>

A property value can be a simple value, or it could be another Object. Example 3 iullustrates using a property that is another object.

<Object1>
	<property1>
		<Object2>
			<property2>value</property2>
		</Object2>
	</property1>
</Object1>

In Example 3 Object 2 is the value of property1 and in this case property1 is called a relationship property. This is because it explains the relationship between Object1 and Object2.

To illustrate this rule again with geotechnical data Example 4 shows two layers Objects within a Hole object without a relationship property between them. In this case a relationship property is added that groups the layer objects together and describes their relationship to the Hole. As with many Objects in DIGGS the relationship property is simply a holder for a group of objects and in this case takes the plural from of the Object (i.e adds an "s" to the end of the object name) Example 5 shows the addition of a layers property to ensure the Object Property relationship rule is observed.

<Hole>
	<Layer>
		<topDepth uom=”m”>2.3</topDepth>
		<description>Firm CLAY</description>
	</Layer>
	<Layer>
		<topDepth uom=”m”>2.3</topDepth>
		<description>Firm CLAY</description>
	</Layer>
</Hole>

<Hole>
	<layers>
		<layer>
			<topDepth uom=”m”>2.3</topDepth>
			<description>Firm CLAY</description>
		</layer>
		<layer>
			<topDepth uom=”m”>2.3</topDepth>
			<description>Firm CLAY</description>
		</layer>
	</layers>
</Hole>