Information System Composition
The information system can be broken down according to two detail levels: application and application system.
Applications
An application is a set of software components constituting a coherent whole regarding deployment, functional coverage and IT techniques used.
The application is the management and deployment unit of a set of software components. An application can be deployed on one or several machines. An application responds to:
• business requirements
Examples: billing, accounting, equipment management, load/capacity calculation.
• technical requirements
Examples: specific communication interface, access control.
• transverse requirements
Examples: electronic mail, directories, office system applications.
Application system
An application system is an assembly of applications responding to a coherent set of functionalities, implemented by the applications making up the system.
Application systems can:
• comprise a suite of applications grouped for commercial reasons (integrated management software packages such as SAP, Oracle Applications, Siebel…) or
• correspond to a group of applications that have the same functional objectives (accounts and financial management system integrating all accounting applications: general, suppliers, analyses, as well as financial and budgetary analysis modules, human resources management systems integrating salaries, time management, career management, etc.).
The application system and application can be the subject of specific developments (carried out internally or bought-in/sub-contracted) or they can be proprietary market products (software packages).
The logical organization and structure of application systems and applications, together with description of their exchanges, constitutes the foundations of the application architecture.
In MEGA Architecture, we use the terms application and application system without distinction to name components of an application architecture.
Applications listing
Breakdown of an application system into sub-applications (or sub-systems) is considered from two main viewpoints:
• on the one hand we consider the software elements provided by the application system (system deployment involves deployment of its components, system development is dependent on development of its components, etc.).
• on the other hand we consider the application in terms of its operation.
In this case we must also include the sub-applications used on execution of the application, but which are not supplied.
We are talking here about applications used explicitly; the user application knows the application used and calls its services directly.
Exchanges between applications