Introduce an "Application Software" element to Technology Layer
Linking this to my comments on the Application Component, it would clarify the ArchiMate framework to introduce another specialisation of the Node, called "Application Software".
This performs the architecturally strong function of separation of concerns, in-so-far as it means we could now model ALL technologies in the Technology layer, rather than confusing the Application Layer with a whole load of technology stuff that has no place there.
For instance the Application Interface should, as it says in the Spec, represent a "logical channel" and then as such represent the "functionality of a component". Including all kinds of Web Service collateral (parameters, protocols) is muddling the whole thing up. As far as the Business Layer is concerned all it needs to know is that it can rely on using an automated set of functions.
The technology layer is already set up to properly address Web Services, user-to-application interfaces such as web pages and much more. And when it comes to replaceability, it is the technology layer that provides this. An organisation could for instance decide to swap its technologies from Java to Microsoft, but this should not a have any impact whatsoever on the logical functions and services in the application layer serving the Business Layer.
Indeed this highlights another big differences in characteristics between Application and Technology - Application functionality is relatively static and has a life span measured in decades, even centuries. But the lifespan of technology can be measured in hardly more than a few years, before the next technological fad comes along.
An Application Software definition could be:
"Application software represents software that implements application components. It is used to create, read, update, delete, manipulate and search for data. It is mapped to the system software and devices that support it."
It can go on to say...
"Application software is a specialisation of a node that is used to model the software used directly in providing functionality to the business. This could for instance be software that handles Customer Relationship Management, Enterprise Resource Planning, Payroll, Business Administration and much more. Usually application software is combined with devices and systems software.
Devices and System Software can be assigned to it. It can also be assigned to the artifacts that enable the application software to be used by people, or interoperate with other application components. Application Software realizes application components. A node can be composed of application software."