A.1.1 Child Node Values
The selection node and all of its child nodes can be referenced by the conditional expression. The value of the selection node can be referenced using the reserved word, 'this'.
this is null
Its immediate child nodes can be referenced by their names,
salary > 50000
The descendents of the child nodes can be referenced with a node path. A node path is constructed by appending the node names from the child node, and all of the nodes leading to the referenced node, with the node names separated by dots. For example, the child of 'location' node can be referenced using:
location.city = 'New York'
Using the same algorithm, a path can be constructed for arbitrary levels down the sub-tree,
child1.grandchild2.grandgrandchild3 like 'N%'
If the referenced node can have multiple instances, the node value is extracted from the first instance of the node. For example, the 'Skill' node in the 'Employee' tree can have more than one instance. An employee can have multiple skills. A 'Skill' node describes each. If the skill child is used in an expression, it refers to the first occurrence of the 'skill' node.
skill like 'Java%'
It is possible to specify the exact instance by adding an index parameter to the node name.
skill like 'Java%'
The index is zero based. If the specified instance does not exist, the node reference returns a null value.
Node names used directly in an expression must not contain any spaces or other special characters. Like identifiers in a programming language, a node name must start with an alphabetic character or '_', followed by zero or more alphanumeric characters. In case a node name does not conform to this requirement, or the name collides with a reserved word, the node can be referenced using the 'node' function,
node('first name') = 'John'
This is functionally equivalent to the direct reference to a node, but allows any node name to be used regardless of the characters in the name.
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