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Various transactions occur within the SSC ICT architecture and between SSC ICT end‐users and the
SSC ICT architecture subsystems. Indicatively, these transactions concern:

1. Information and service requests (demand side end‐users);
2. Information and service delivery (supply side end‐users and sub‐systems);

3. Information and service requests (demand side subsystems);

4. Information and service delivery (supply side subsystems);
5. Information storage (demand side subsystems);
6. Information retrieval (supply side subsystems).

Individual interfaces stand around each subsystem and interconnects it with the others, while
separate user interfaces offer service options to its end‐users (demand and supply side) in order for
a transaction to be performed.

7 Indicative SSC ICT architectural snapshots from

different views

7.1.1 A software engineering view of the SSC ICT architecture
According to [14] a multi‐tier architecture can satisfy the SSC ICT architecture. More specifically, a
5‐level approach introduces sufficient flexibility (Figure 7) due to following reasons:

 In a two‐tier architecture, the user interface and business logic are tightly coupled while the data
is kept independent. This allows the data to be independently maintained. The tight coupling of
the user interface and business logic assure that they will work well together – for this problem
in this domain. However, the tight coupling of the user interface and business logic dramatically
increases maintainability risks while reducing flexibility and opportunities for reuse.

 A three‐tier approach adds a tier that separates (an amount of) the business logic from the user
interface. This in principle allows the business logic to be used with different user interfaces as
well as with different data stores. With respect to the use of different user interfaces, users
might want the same user interface but using different commercial off‐the‐shelf (COTS)
presentation servers, for example, thin client, Java Virtual Machine (JVM) or Common Desktop
Environment (CDE).
 Similarly, if the business logic is to be used with different data stores, then each data store must
use the same data model (''data standardization''), or a mediation tier must be added above the
data store (''data encapsulation'').

 An additional level of flexibility can be achieved using a 5‐tier scheme for software, extending
the three‐tier paradigm.

360 ITU‐T's Technical Reports and Specifications