IT system architecture

The IT system architecture entry point is the application map or the application portfolio. All IT systems in a company are represented in a model of the Application system type diagram type and, if necessary, grouped in application domains. IT systems are described in more detail in assigned models (level 3-n of the architecture pyramid).

The division into domains is made possible by the Application system class object type, to which the corresponding IT systems or IT subsystems are assigned. The assignment of IT systems to individual domains and the division of an application into several subsystems can be specified in more detail across several levels. Architecture projects often begin with recording and documenting the as-is application map.

The application system manager is responsible for regularly updating the information about an IT system.

The type level, also called the 'logical view', contains information about the underlying operating system, the programming language, the database used, the hardware type, the organizational unit responsible, and about the application system manager himself. The information is represented in an access diagram assigned to the system.

The architecture set (see chapter IT technology architecture) serves as a library, from which the system manager takes all IT components in order to describe a system. This ensures that only IT components recorded and evaluated by the IT architect role are used, which guarantees a high level of standardization.

Persons and organizational units responsible are taken from the models of the organization view and can be linked to the IT system (application system type) by a corresponding relationship. The application manager can achieve a detailed specification of the role of the person or organizational unit by assigning the is responsible for connection the connection attribute Responsibility type.

Other characteristic features of an IT system can be specified by assigning corresponding attributes to the system itself.

Heterogeneous IT landscapes are characterized by a multitude of interfaces between IT systems. Interfaces are represented at two levels of abstraction. The first level always represents an IT system with all IT systems that are connected via interfaces. The program flow chart can be used for this purpose. The transmits data to relationship illustrates that an interface exists between two systems.

The interface can be specified in detail in a model of the Program flow chart type assigned to the transmits data to connection. In addition to the data flows via the interface, the relevant transmission protocol is taken into account. A new relationship, including another assigned model, is created for each protocol and direction.

As already explained in the chapter Business processes, system functions (capabilities) form the bridge between the IT system landscape and the business processes. Each system is therefore specified with regard to the supported system functions. This is done either in the above-mentioned access diagram along with other relevant system information, or in an application system type diagram provided specially for this purpose.

The system functions are ideally taken from a library. The service architecture diagram can be used to represent this library.

If all systems are described using system functions from this library, a wide range of analysis options is available to the architecture manager. The architecture manager can, for example, determine IT system redundancies or identify system requirements. This can be done by simply using the Relationships tab or by running the corresponding standard report.

In the following figure, the Relationship tab shows that the Price calculation system function is provided by three IT systems, namely A-PLAN, HLPN-1, and PRO-ORDER.

To document the required system support from a business process perspective, system functions can also be derived from processes. They are therefore an essential component of requirements management (see chapter System functions, requirements, project and portfolio management).