Network Configuration Management with NETCONF and YANG - IETF

Augment, Must, When, Presence
⊲ augment:
The augment statement places nodes into an existing
hierarchy using the current module’s namespace.
⊲ must:
The must statement expresses constraints (XPath
expressions) that must be satisfied by a valid
configuration.
⊲ when:
The when statement can be used to define sparse
augmentations where nodes are only added when a
condition (XPATH expression) is true.
⊲ presence:
The existance of a presence container carries a certain
meaning (a single bit of configuration data).
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