When integrating with legacy systems, XML might be preferred due to its rich schema definition and strong data typing. XML allows for precise data representation, which is crucial for interoperability and compatibility with existing systems that may rely on specific data structures.

GraphQL introduces the concept of subscriptions, enabling real-time data updates, a feature not inherent in traditional REST APIs.

Header Versioning is more manageable for extensive API versioning, as it keeps version information separate from the URI, promoting cleaner and more flexible URLs.

OAuth is commonly used for authorization in web service security. It allows secure and controlled access to resources by enabling a token-based authentication mechanism. OAuth is widely employed in scenarios where third-party applications require limited access to a user's resources without exposing sensitive credentials.

In the initial phase of transitioning to SOA, the primary focus should be on identifying key services and their dependencies. This helps establish a clear understanding of the existing landscape and lays the foundation for a well-organized and effective SOA implementation.

The use of TLS in HTTPS enhances the security of web services by providing data encryption and integrity. TLS (Transport Layer Security) ensures that the communication between clients and servers is secure, protecting against eavesdropping and tampering of data during transmission.

In RESTful services, a 404 error indicates that the requested resource was not found.

SoapUI is a widely used tool for simulating the behavior of web service components in integration testing.

Dynamic resource allocation is a technique in web services that dynamically allocates resources to handle varying loads efficiently.

Adhering to RESTful architecture is a best practice for ensuring web services are scalable and maintainable, promoting loose coupling and scalability.