DevOps is a cultural and operational philosophy focused on unifying software development (Dev) and IT operations (Ops). A foundational principle is the cultural shift away from siloed departments toward cross-functional teams where developers and operations personnel collaborate and share responsibility throughout the entire service lifecycle. Another core tenet is the extensive automation of processes, especially the software delivery pipeline (Continuous Integration/Continuous Delivery), to accelerate delivery, improve reliability, and reduce manual errors. These principles of culture (collaboration) and automation are central to achieving the goals of DevOps.

A. Microservices are a common architectural pattern that complements DevOps but are not a mandatory foundational principle; DevOps can be applied to monolithic applications.

B. Containers are a technology that enables key DevOps practices like consistency and portability, but they are a tool, not a foundational principle of the methodology.

D. Cost optimization is a frequent and desirable business outcome of implementing DevOps efficiently, but it is not a core principle itself.

1. Cisco DevNet Learning Labs, "DevOps Explained," Module: What is DevOps? This official Cisco training material states, "DevOps is a set of practices that combines software development (Dev) and IT operations (Ops). It aims to shorten the systems development life cycle and provide continuous delivery with high software quality. DevOps is complementary with Agile software development; several DevOps aspects came from Agile methodology... The main characteristics of DevOps are automation and culture." This directly supports automation (E) and the cultural aspect of breaking down silos (C).

2. Amazon Web Services (AWS), "What is DevOps?" Documentation. AWS, a major industry authority, defines DevOps through its cultural philosophies and practices. It states, "DevOps is the combination of cultural philosophies, practices, and tools..." Under "DevOps Cultural Philosophies," it emphasizes "Improved Collaboration," which aligns with creating cross-functional teams over silos (C). Under "DevOps Practices," it lists "Continuous Integration and Continuous Delivery" (CI/CD), which is the embodiment of automation (E) in the software lifecycle.

3. Google Cloud, "What is DevOps?" Documentation. Google's official documentation describes DevOps as "a set of practices, tools, and a cultural philosophy that automate and integrate the processes between software development and IT teams." It explicitly mentions the importance of "breaking down data and workflow silos" (C) and highlights "automation" (E) as a key method to increase speed and reliability.