Which of the following can be considered PaaS offering?

Concept: Cloud services are classified by how much the vendor manages for the customer. SaaS delivers a complete, ready-to-use application straight to end users, who only consume it. PaaS instead delivers a development platform — APIs, tools, and building blocks — on top of which other developers build their own applications; the customer is a developer, not just a consumer.

Application: Among the four services listed, Google Maps is the one that functions as a platform: it exposes mapping and location APIs that other developers build their own applications on top of, rather than being consumed only as a finished end-user product. That developer-facing, build-on-top role is what places it in the platform (PaaS-style) category being asked about here, distinguishing it from the other three, which are complete applications handed directly to end users.

• Youtube: a complete, ready-to-use video-streaming application consumed directly by end users — a finished product, not a platform.

• Google Earth: a complete, ready-to-use geographic-visualization application for end users — again a finished product, not a platform.

• Google Adsense: a complete advertising-management service delivered directly to businesses — a finished product, not a development platform.

Note: some classifications instead treat Google Maps as SaaS or an API-as-a-service; among the options offered here, however, it is the standard, widely-used convention across cloud-computing question banks to mark it as the platform-style (PaaS) choice.