Information Technology Reference
In-Depth Information
6.2.1
Technology Objects
The technology specification describes the implementation of the ODP
system in terms of a configuration of technology objects (representing the
hardware and software components of the implementation) and the interfaces
between them. These objects are constrained by the cost and availability of
satisfactory technology products.
Technology objects are normally specified in terms of their types. Exam-
ples of such types include the kinds of PCs, servers, ATMs, printers and other
hardware devices that can be used to implement the system and execute its
functionality. Giving a clear definition of these types helps in answering ques-
tions such as whether we are going to count on there being colour printers
available or not, or whether our system will run some particular services on
a central server, on a PC or from an external cloud computing system. The
technology specification also describes the types of operating systems and ap-
plications (such as browsers or text editors, for example) and the types of
connections (LANs, WANs, intranets and so on) that will be used for deploy-
ing the engineering channels.
For example, figure 6.1 shows the technology configuration of the
PhoneMob system using the UML4ODP notation. It is described using a
UML deployment diagram that specifies the deployment architecture of the
system by showing the different technology object types that will be used and
how they can be connected. In a deployment diagram, a computer node is
expressed as a node and lines are introduced to express interfaces between the
nodes. Different types of network are also depicted as nodes. The diagram
shows that there will be three different kinds of computing resource (PCs, en-
terprise application servers and backend business servers), two different kinds
of communication media (LAN and WAN) and, as special peripherals on the
PCs, printers and barcode readers. PCs and enterprise application servers can
be connected to LANs and WANs, whilst backend business servers can only
be connected to isolated LANs under the control of a firewall. Connections to
the WAN are also achieved through the firewall.
The technology selection has clear consequences. For example, the types
of the technology objects used may affect the provision of quality of service.
They determine the performance costs of interactions and thus, indirectly,
the quality of service which can be achieved by the behaviour defined in other
viewpoints. The selection may also affect the way in which functionality needs
to be developed, and even the software architecture of the application. For
example, some technological platforms such as JEE or .NET impose particular
architectural styles (such as client-server or multi-layered) and provide some
common functions and services. Other platforms may not provide all the
necessary services and thus any that are missing must be implemented by
adding code each time they are needed.
