Which of the following service models involves end-user applications delivered over the internet?

The service model that involves end-user applications delivered over the internet is Software as a Service (SaaS). This model allows users to access software applications hosted on the cloud, eliminating the need for local installation and maintenance. With SaaS, the software is typically provided on a subscription basis, and updates and management are handled by the provider.

SaaS applications are accessible from various devices with internet connectivity, allowing for greater flexibility and collaboration among users. Common examples of SaaS include email services like Gmail, customer relationship management tools like Salesforce, and office productivity suites like Microsoft 365. This approach simplifies deployment for organizations since they do not have to worry about infrastructure, application updates, or hardware, as these elements are managed in the cloud.

The other service models—Infrastructure as a Service (IaaS) and Platform as a Service (PaaS)—focus on providing infrastructure and platforms for developers rather than end-user applications. Data as a Service (DaaS), while also a useful cloud service model, specifically relates to the provision of data rather than complete application software. Hence, SaaS is distinctly the correct answer in this context.