Capability is not a Behavior

Whatever it is, a Capability is definitely not a Behaviour. It’s probably best classified as a Composite in ArchiMate terms. These are the main reasons:

• A Capability is a property of a system. Any system “has” certain Capabilities. A person with the capability to play tennis possesses a property which enables them to play tennis – a “Tennis Playing capability”. “Play Tennis” is the behaviour, not the “Tennis Playing” capability.
• Capabilities are always expressed as nouns, i.e. they are ‘things’, properties, attributes not behaviours, operations or methods.
• The ArchiMate definition itself suggests it’s a property, “an ability … a system … possesses”, so classifying this as a behaviour was a bizarre choice, which I believe was mainly influenced by the pre-existing classification of “Business Function” as a Behaviour (which, btw, is also inappropriate).
• A Capability is an emergent property of a system; i.e. a Capability is a property that emerges from a combination of things, the celebrated phrase “the whole is greater than the sum of the parts”. Traditionally in enterprises this is seen as the combination of People, Process and Technology. Process is the behaviour, executed by People and supported by Technology. From the combination emerges the sought-after Capability - in particular knowledge of how to execute a behavior is a key ingredient in the emergent property. In ArchiMate these things are modelled in the Core Layers, realizing a Capability identified in the Strategy Layer.