REST APIs

This topic covers designing web APIs. You map operations onto HTTP verbs, choose appropriate status codes, understand idempotency and statelessness, and handle cross-cutting concerns like versioning and rate limiting.

Relation 1 —

Write this relation with symbols exactly as in Deitel Web Dev — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 2 —

Write this relation with symbols exactly as in Deitel Web Dev — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 3 —

Write this relation with symbols exactly as in Deitel Web Dev — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

REST leans on HTTP’s existing semantics rather than inventing new ones: each resource has a URI, and the verb expresses the action — GET reads, POST creates, PUT replaces, DELETE removes. The idempotency distinction matters for reliability: a client can safely retry an idempotent GET, PUT or DELETE after a network failure because repeating it has no additional effect, whereas repeating a POST may create duplicates. Statelessness means each request is self-contained, which makes REST APIs easy to scale and cache. Meaningful status codes let clients react correctly (201 for a created resource, 404 for a missing one), and rate limiting guards shared backends.

State assumptions explicitly before using any relation for rest apis — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.

Wrong assumptions invalidate the entire solution even when the formula is correct. In Web Technologies viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

1. Read the question and list given data with SI units (common in Web Technologies papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to rest apis.
4. Use equation 1: .
5. Use equation 2: .
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

REST APIs appears in web apps and REST APIs. In Indian it software curricula this topic is tested because it connects theory to front-end and back-end web stack.

GATE and semester exams often combine rest apis with earlier units — revise prerequisites before attempting mixed problems.

Industry interview panels sometimes ask: "Where did you use rest apis?" — answer with a lab, mini-project, or plant visit example if possible.

Students misclassify POST as idempotent, use the wrong verb (GET to modify data), and return 200 for every response regardless of outcome. Making an API stateful (server-side session between calls) contradicts REST principles.

Before attempting rest apis problems, confirm you can:

1. Status codes: 200 OK, 201 Created, 404 Not Found
2. Versioning via URL path or the Accept header
3. Rate limiting protects the backend from abuse

Revise the solved examples in Deitel Web Dev — Standard reference and one previous-year GATE or university paper for this unit.