Information Technology Reference
In-Depth Information
ing to all parties. In this viewpoint the focus is on the information itself,
without considering further platform-specific or implementation details, such
as how the data is represented, implemented or distributed. The information
viewpoint is also independent from the computational interfaces and functions
that manipulate the data, or the nature of the technology used to store it. In
this way, what we get is a common abstract model for the shared information
in the system, which can be used to ensure its consistent interpretation by all
stakeholders.
Thus, the objective of this viewpoint is similar to the aim in having data
dictionaries for achieving interoperability between all interested parties, or the
goal of ontologies for providing a common and unique interpretation of the
shared information entities of a particular domain.
The information viewpoint should be able to answer a set of questions
about the system, such as: \What are the data types of the information that
the system will handle?" \What are the relationships between these types?"
\How will the state of the data in the system evolve as the system operates?"
\What are the allowable actions that the system will accept, and how will
they aect the state of the data?" or \What are the constraints on the data
and its processing?"
To respond to these questions, the information viewpoint uses the infor-
mation language, which provides a set of elements and constructs to model
the information specification of a system.
3.2 The Elements of the Information Language
An information specification defines the information handled by the system
and the rules governing the processing of such information. It does this by
defining a configuration of information objects, the behaviour of these objects,
the actions that can happen and a set of constraints that should always hold
for this collection of elements. Let's describe each of these elements, one by
one.
Information objects model the data handled by the ODP system about
entities in the real world. Information objects, just like any other ODP objects,
exhibit identity, state and behaviour, and interact with other information
objects. Examples of information objects are the handset with serial number
"SN33433/09"
, the user called
"JoeSmith"
, or the repair order with number
"2010-VIP-0003"
.
Every information object has a type, which is a rule (strictly speaking, a
predicate) that characterizes the set of objects that share a common set of
features and a given behaviour. Information object types can be considered
to be similar to abstract data types in programming languages. Examples of
information object types are Handset, User or RepairOrder.
