Which of the following is not a source of request attributes?

Request attributes are key components used to provide context about web requests in application monitoring and performance management. These attributes are essential for identifying, categorizing, and tracking requests as they pass through various components of an application.

URL parameters represent data sent in the URL that can influence the behavior of the application. For example, a query string in a URL might dictate which records are returned in a database query.

HTTP headers contain metadata about the request, such as content types and authorization credentials. They carry important information that can help in understanding the context of the request and how it should be processed.

POST parameters are data sent in the body of an HTTP POST request. They typically carry form data submitted by users, allowing applications to receive and process information such as user input.

In contrast, system logs do not directly pass along attributes about individual requests. While they may contain information related to requests, such as timestamps or error messages, they serve primarily as logs of system events rather than active components of how requests are processed or tracked within a session. Therefore, they do not qualify as direct sources of request attributes in the context of application monitoring.