Application Layer

The Application Layer elements are typically used to model the Application Architecture that describes the structure, behaviour, and interaction of the applications of the enterprise. The Application layer elements answer the How? question, defining application components, interfaces, services and functions.

From the ArchiMate® application layer element set, this reference architecture implements the following elements:

Element	Description	Notation
Application component	Represents an encapsulation of application functionality aligned to implementation structure, which is modular and replaceable.
Application interface	Represents a point of access where application services are made available to a user, another application component, or a node.
Application function	Represents automated behaviour that can be performed by an application component.
Application event	Represents an application state change.
Application service	Represents an explicitly defined exposed application behaviour.
Data object	Represents data structured for automated processing.

The main focus of the eArchiving Building Block is interoperability. Our approach, therefore, follows a top-down logic and intends to define those elements of the Reference Architecture in detail that are more important from an interoperability point-of-view.

The application layer is the downmost layer implemented in the reference architecture. The application elements and especially the component structure are less relevant from an interoperability aspect. The main purpose of modelling the application layer is twofold:

• positioning the E-ARK specifications and eArchiving Sample software within the reference architecture and link them to the appropriate business processes,

• provide the end users of the reference architecture with the capability of mapping their own application elements with the reference architecture serving as a reference point of comparison.

The views of the application layer are structured according to the corresponding OAIS functional entity and extended with Pre-Ingest:

• Overview (a wall-to-wall view covering the archival life cycle from pre-ingest to access)

• Pre-Ingest

• Ingest

• Access

Example scenarios

We have added some example component structure diagrams to the application layer. The scenarios include real-world component structure examples from three national archives and the component structure of the ESSArch digital archiving solution. These scenarios all implement state-of-the-art full scale digital archiving solutions.