This is my understanding of the Application Layer:
• It implements Application logic
• this layer contains Application Services, which are used by external consumers to talk to your application
• Application Services are coarse-grained and orchestrate operations which map directly to use cases ( hence also the term Workflow Services )
Application Logic is mostly workflow logic. It is the application specific coordination of domain and infrastructure components according to the requirements of that particular application.
Let's start a company, shall we? Sapient Grey will be primarily a think tank, but with an in-house development group with the capabilities to make the visions of the core committee a reality. Our corporate motto, "Sapient Grey is People..." will be burnished in giant brazen letters alongside a customized version of Rodin's famous sculpture "The Thinker", all of which will adorn the east-facing side of our brand new ten story red granite office building.... Oh, wait. We don't have an office building yet. Okay then, so we'll hire an architect to design our office building, being sure to include a private elevator and an elaborate zen-style atrium or courtyard in the center. In the meantime, while the building is being designed and constructed, you and I and our other elite colleagues will fly ourselves to Tahiti to brainstorm Sapient Grey's visions, goals, agenda, and lay out a detailed business plan.
Our architect is creating detailed blueprints for the office building, figuring out how the plumbing will need to be laid out, how the electrical systems will be segregated and tied together, how the interoffice communication system will be organized, and how we will implement security at all levels. The systems and designs that our building architect is handling is a precise analogy to what "Application Logic" is within a web application. How security is implemented, how we will manage and access state and persistence, how we will handle storage and retrieval of data....this is application logic. Like our office building, which when complete could house and accommodate anything from an elite night club to an investment firm, the application logic is independent of the actual business logic that executes within it.
a) The above quotes are two different definitions of the term Application Logic and as such it appears they just happen to use the same term (ie Application logic) to describe two different concepts. Thus, does only the the first definition describe the logic contained in Application layer, while the latter definition is describing a different kind of logic?
b) If indeed both definitions describe the logic in Application layer, then wouldn't this mean that Application layer performs two tasks: orchestrating operations that map directly to use cases and executing non-business related logic (such as security, caching etc)?