Platform as a Service (PaaS) is the cloud service model where a third-party provider delivers a platform for customers to develop, run, and manage applications. This platform includes the underlying infrastructure (servers, storage, networking) as well as the necessary application infrastructure, such as middleware, development tools, database management systems, and business intelligence services. The consumer manages their own applications and data but does not manage the operating systems, hardware, or the platform software itself. Consuming "application infrastructure (middleware)" is the defining characteristic of the PaaS model.

B. MaaS: Monitoring as a Service (MaaS) is a specialized cloud service focused on providing monitoring capabilities for applications and infrastructure, not the core application development platform itself.

C. DaaS: Desktop as a Service (DaaS) provides a virtual desktop infrastructure to end-users over a network. It is concerned with user desktops, not application development middleware.

D. SaaS: Software as a Service (SaaS) delivers complete, ready-to-use software applications over the internet. The consumer uses the application but does not manage or develop on the underlying platform.

1. Mell

P.

& Grance

T. (2011). The NIST Definition of Cloud Computing (Special Publication 800-145). National Institute of Standards and Technology. Retrieved from https://doi.org/10.6028/NIST.SP.800-145

Reference Point: Page 2

Section "Service Models

" defines Platform as a Service (PaaS): "The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages

libraries

services

and tools supported by the provider... The consumer does not manage or control the underlying cloud infrastructure..." This directly describes providing an application platform

including middleware.

2. Armbrust

M.

Fox

A.

Griffith

R.

Joseph

A. D.

Katz

R.

Konwinski

A.

... & Zaharia

M. (2010). A view of cloud computing. Communications of the ACM

53(4)

50-58. https://doi.org/10.1145/1721654.1721672

Reference Point: Page 53

Section 3.1

"Classes of Utility Computing

" describes PaaS as providing "an abstraction that is a platform on which the developer builds an application." It explicitly contrasts this with SaaS (delivering a complete application) and IaaS (delivering raw machine resources).

3. Massachusetts Institute of Technology. (2018). 6.033 Computer System Engineering

Spring 2018 - Lecture 21: Cloud Computing. MIT OpenCourseWare.

Reference Point: In the lecture notes and slides for Cloud Computing

PaaS is defined as offering a higher-level abstraction than IaaS

providing a complete development and deployment environment

which includes middleware

databases

and other application services. This aligns with the scenario in the question.