Final answer:
The item not part of application architecture is 'virtual private networks'; it pertains to network infrastructure. Application architecture encompasses software, development tools and languages, and user-interface technology critical for the application's function and design.
Step-by-step explanation:
The item that is NOT a part of the application architecture among the options given is virtual private networks (VPNs). Application architecture generally consists of the software, the programming languages and development tools used to create it, and the user-interface technology that defines how users interact with the software. In contrast, a VPN is a network configuration that allows for secure communication over public networks and is not specific to a single application's design. It is more related to the infrastructure supporting the application rather than the application itself.
When addressing the quality of a design, engineers often evaluate product attributes and perform adequate testing on prototypes. This helps determine if the application meets the required standards and functions as intended. The thorough testing of prototypes is crucial for ensuring the quality of a design before it is deployed or released to users.