- A
YANG is used to model both configuration and operational state data.
Correct because YANG models can include both config true and config false nodes for configuration and state data.
- B
YANG models can be augmented using the 'augment' statement.
Correct because the 'augment' statement allows extending an existing YANG module with additional nodes.
- C
YANG defines the transport protocol for data exchange.
Why wrong: Incorrect because YANG is a data modeling language and does not specify transport; NETCONF or RESTCONF provide the transport.
- D
The 'leaf' statement in YANG defines a list of key-value pairs.
Why wrong: Incorrect because 'leaf' defines a single scalar value; 'list' defines a collection of key-value pairs.
- E
YANG uses XML or JSON encoding for data instances.
Correct because YANG data can be encoded in XML (as in NETCONF) or JSON (as in RESTCONF).
Quick Answer
The correct statements about YANG data models include that YANG uses XML or JSON encoding for data instances, defines both configuration and operational state data, and supports augmentation through the 'augment' statement. YANG is a data modeling language that structures network device data, separating writable configuration from read-only operational state, which is critical for NETCONF and RESTCONF implementations. On the ENCOR 350-401 exam, this topic tests your understanding of how YANG models are applied in automation and programmability, often appearing in questions that require distinguishing between leaf, list, and container statements. A common trap is confusing YANG’s role with transport protocols—remember that YANG defines the data model, not the protocol. For a memory tip, think of YANG as the blueprint: it tells you what data looks like (XML/JSON), what it does (config vs. state), and how to extend it (augment), but it never drives the delivery truck.
350-401 REST APIs and Data Models Practice Question
This 350-401 practice question tests your understanding of rest apis and data models. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which three statements about YANG data models are true? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
YANG is used to model both configuration and operational state data.
YANG is a data modeling language used to model configuration and state data for network devices. It can define both configuration data (which is writable) and operational state data (which is read-only). YANG models can be augmented using the 'augment' statement to add nodes to an existing model without modifying it. YANG does not define transport protocols; it is used with protocols like NETCONF and RESTCONF. The 'leaf' statement defines a single, scalar data node, not a list.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
YANG is used to model both configuration and operational state data.
Why this is correct
Correct because YANG models can include both config true and config false nodes for configuration and state data.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
YANG models can be augmented using the 'augment' statement.
Why this is correct
Correct because the 'augment' statement allows extending an existing YANG module with additional nodes.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
YANG defines the transport protocol for data exchange.
Why it's wrong here
Incorrect because YANG is a data modeling language and does not specify transport; NETCONF or RESTCONF provide the transport.
- ✗
The 'leaf' statement in YANG defines a list of key-value pairs.
Why it's wrong here
Incorrect because 'leaf' defines a single scalar value; 'list' defines a collection of key-value pairs.
- ✓
YANG uses XML or JSON encoding for data instances.
Why this is correct
Correct because YANG data can be encoded in XML (as in NETCONF) or JSON (as in RESTCONF).
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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REST APIs and Data Models — study guide chapter
Learn the concepts, then practise the questions
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REST APIs and Data Models practice questions
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FAQ
Questions learners often ask
What does this 350-401 question test?
REST APIs and Data Models — This question tests REST APIs and Data Models — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: YANG is used to model both configuration and operational state data. — YANG is a data modeling language used to model configuration and state data for network devices. It can define both configuration data (which is writable) and operational state data (which is read-only). YANG models can be augmented using the 'augment' statement to add nodes to an existing model without modifying it. YANG does not define transport protocols; it is used with protocols like NETCONF and RESTCONF. The 'leaf' statement defines a single, scalar data node, not a list.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which three statements about YANG data models are true? (Choose three.)
hard- ✓ A.YANG is used to define data models for NETCONF and RESTCONF.
- B.YANG models are written in XML syntax.
- ✓ C.YANG supports hierarchical data structures using containers and lists.
- D.YANG modules are compiled into MIB files for SNMP.
- ✓ E.YANG includes built-in data types such as string, int32, and enumeration.
Why A: The correct answers are A, C, and E. A is correct because YANG is used to model configuration and operational data in NETCONF and RESTCONF. C is correct because YANG uses a tree-like hierarchical structure with containers and lists. E is correct because YANG supports data types such as string, int32, and enumeration. B is incorrect because YANG models are not written in XML; they use a custom syntax similar to SMIv2. D is incorrect because YANG modules are not compiled into MIB files; MIBs are for SNMP.
Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
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