System Scope and Context

Contents

System scope and context - as the name suggests - delimits your system (i.e. your scope) from all its communication partners (neighboring systems and users, i.e. the context of your system). It thereby specifies the external interfaces.

If necessary, differentiate the business context (domain specific inputs and outputs) from the technical context (channels, protocols, hardware).

Motivation

The domain interfaces and technical interfaces to communication partners are among your system’s most critical aspects. Make sure that you completely understand them.

Form

Various options:

Context diagrams
Lists of communication partners and their interfaces.

Business Context

Contents

Specification of all communication partners (users, IT-systems, …) with explanations of domain specific inputs and outputs or interfaces. Optionally you can add domain specific formats or communication protocols.

Motivation

All stakeholders should understand which data are exchanged with the environment of the system.

Form

All kinds of diagrams that show the system as a black box and specify the domain interfaces to communication partners.

Alternatively (or additionally) you can use a table. The title of the table is the name of your system, the three columns contain the name of the communication partner, the inputs, and the outputs.

Table 1. System actors
Actor	Description
Manufacturer	The manufacturer of the hardware may update firmware without interaction of the device owner
Owner	The owner controls the home entertainment system via various controls
Viewer	Audio and visual information from the system is consumed by the Viewer (which may be identical to the Owner)
TV Broadcast	TV content is distributed to the system via a broadcasting service over Satellite

Technical Context

Contents

Technical interfaces (channels and transmission media) linking your system to its environment. In addition a mapping of domain specific input/output to the channels, i.e. an explanation with I/O uses which channel.

Motivation

Many stakeholders make architectural decision based on the technical interfaces between the system and its context. Especially infrastructure or hardware designers decide these technical interfaces.

Form

E.g. UML deployment diagram describing channels to neighboring systems, together with a mapping table showing the relationships between channels and input/output.

Table 2. Technical Interfaces
Interface	Description	I/O
Audio	The system generates audio information and outputs it via speakers to the Owner	out:Soundwaves
Video	Visual information is tranferred to the Owner	out:Light
LAN	Local area network connection is used for communication between the Owner and the system	in:media control
WAN	An internet connection is used by the system to update its firmware via the Manufacturer or to fetch online content	out:HTTPS
Remote Control	A remote control is used by the Owner to modify the system state	in:physical interaction
Satellite	Using the `DVB-S` standard television program from the TV broadcast is received	in:DVB-S