List versus Leaf-List nodes in YANG

[Mitrixsen]

Hello, everyone.

I am studying automation for my ENCOR exam.

I have a quick question - what is the difference between a leaf-list node and a list node in YANG models? Google defines them as:

Leaf-list node — Contains a sequence of leaf nodes
List node — Contains a sequence of list entries, each of which is uniquely identified by one or more key leafs

I am a bit confused about the explanations above, they seem somewhat the same to me. Could someone please tell me what is the major distinction here? Both represent some form of a list/array that contains multiple nodes, right?

Thank you
David

[Enes Simnica · Accepted solution]

hello G. 

• Leaf-list = Simple array of single-value items (like [10, 20, 30]). Example: VLAN lists.
  List = Structured table with keyed entries (like [{name: "Gi0/1", mtu: 1500}, {...}]). but some more key difference would be that Leaf-list values have no sub-fields, and also List entries have multiple attributes and require unique keys...
  Example YANG:

leaf-list vlans { type uint16; }  // Simple values
list interface {                  // Structured data
  key "name";
  leaf name { type string; }
  leaf mtu { type uint16; }
}

and for Encor I'd say use leaf-list for basic value arrays and for complex configurations needing keys

check these links G; 

• https://datatracker.ietf.org/doc/html/rfc6020#section-7.6
• https://www.cisco.com/c/en/us/support/ios-nx-os-software/ios-xe-17/products-installation-and-configuration-guides-list.html#!yang-overview 

• https://developer.cisco.com/docs/nso-guides-6.3/the-yang-data-modeling-language/ 
• https://www.youtube.com/watch?v=zy9QA-uU0u4 

hope it helps\

-Enes

[bigevilbeard · Accepted solution]

They way I finally got this was, thinking like  leaf list is like a simple array of single values [“a”, “b”, “c”] but a list like a array of objects, where each object has properties, multiple fields [{name: “eth0”, mtu: 1500}, {name:”eth1”, mtu: 9000}]

Hope this helps.

[M02@rt37 · Accepted solution]

Hello David,

First, a leaf node hold a single, simple value (like an integer or string) and has no child nodes.

-> A leaf-list node is a collection of such leaf nodes _ each entry contain exactly one value of a specific type, essentialy forming a flat list of simple values.

On the other hand, a list node is more complex: it defines a sequence of structured entries (like records), each uniquely identified by one or more key leaf nodes. Each entry in a list node can have multiple child node of any type, making it suitable for representing more detailed/hierarchical data structure.

--https://support.huawei.com/enterprise/en/doc/EDOC1100332772/eefbe002/node-types-of-a-yang-model