Which of the following statements about the YANG data modeling language is FALSE?

The statement that a YANG data model is not human-readable is false. YANG (Yet Another Next Generation) is specifically designed with a human-readable syntax, which is often compared to C-style programming languages. It uses indentation, curly braces, and clear keywords (like container, leaf, list) to define a hierarchical data structure. This readability is a key feature, allowing network engineers and developers to easily understand, create, and manage the data models for network devices. The other statements accurately describe core features of the YANG language.

A. Data is in the form of a tree-like structure. This is incorrect because YANG models are inherently hierarchical. Data is organized into a tree of nodes using constructs like container, list, and leaf, which is fundamental to its design.
B. It is used to model configuration and state data. This is incorrect because a primary function of YANG is to model both configuration data (read/write) and operational state data (read-only), explicitly distinguishing between them using the config statement.
D. Defines actions and operations. This is incorrect because YANG includes specific statements, such as rpc and action, to define custom operations that can be invoked on a managed device via protocols like NETCONF.

1. RFC 7950: The YANG 1.1 Data Modeling Language.

Section 1, Introduction: "The YANG language is designed to be readable by humans..." This directly refutes option C.

Section 1, Introduction: "The data model defines a hierarchy of data that can be used for NETCONF-based operations..." This confirms the tree-like structure mentioned in option A.

Section 7.21.1, The config Statement: "The "config" statement takes as an argument the string "true" or "false". If "config" is "true", the node represents configuration. If "config" is "false", the node represents state data." This supports the statement in option B.

Section 7.15, The rpc Statement & Section 7.16, The action Statement: These sections detail how YANG is used to define Remote Procedure Calls (RPCs) and actions, confirming the capability described in option D.

2. Nokia SR OS 22.10 R1 Data Model, RPC, and Notification Reference.

Chapter 1, Introduction: This document describes the use of YANG models for the Nokia Service Router Operating System (SR OS). It states, "The SR OS NETCONF/YANG solution provides a programmatic interface for device configuration and operations." This implicitly supports that YANG is used for configuration (B) and operations (D) in a real-world, vendor-specific context relevant to the exam. The document itself contains numerous human-readable YANG model examples.