network level. To adapt the framework to the
modelling requirements for telecom systems,
a number of enhancements had to be made as
briefly described below. This enhanced RM-
ODP framework[G.851.1] provides an object-
oriented framework for the modelling of dis-
tributed management systems. The OSI Manage-
ment Framework was not chosen, partly due to
its weakness in providing mapping to manage-
ment requirements and the lack of support for
distribution.
The salient features of a distributed system are
described in terms of five viewpoints:
- Enterprise Viewpoint;
- Information Viewpoint;
- Computational Viewpoint;
- Engineering Viewpoint;
- Technology Viewpoint.
These viewpoints are self-contained, orthogonal
specifications of a system. Additionally, certain
relationships between the viewpoints need to be
fulfilled to preserve the integrity of the overall
system.
The main enhancement to RM-ODP consists of
introducing a finer modelling granularity into the
Enterprise Viewpoint to reflect the granularity of
the network resource types of [G.805]. Also, all
constructs of all viewpoints have been provided
with unique labels for backward traceability to
the functional requirements defined in the Enter-
prise Viewpoint. This is a fundamental mecha-
nism for the support of conformance testing, and
also for estimating the cost of implementation
related to particular requirements.
Because the target application is a model for
management, only the system aspects subject to
management, i.e. the management requirements,
need to be represented in the model. The man-
agement requirements are expressed in terms of
actions with associated policies (enforcements
or restrictions). This is done in the Enterprise
Viewpoint and implies that the requirements
become an integrated part of the model itself.
Another implication is that the Enterprise View-
point becomes a repository for management
requirements, i.e. the management specification
per se.
3.2.1 The Enterprise Viewpoint
The Enterprise Viewpointdescribes the open,
distributed system in terms of the purpose, scope
and policies of the system. It allows the invoker
to express its functional requirements in terms
of actions and policies on the actions to be per-
formed by the provider, thereby establishing the
contract between the invoker and the provider.
[G.852.2] specifies the Enterprise Viewpoint
description of a transport network resource
model. A Resourcein this context is one of the
architectural components defined in [G.805] to
be managed at the network level by a transport
network level management service.The resources are structured into Enterprise
Objectsthat support Actions. The objects, or
rather the roles (a role is a fraction of the object
behaviour) that the objects play, interact through
the actions.The main purpose of the Enterprise Viewpoint is
to identify the network resources and the associ-
ated policies necessary to fulfil the management
requirements. A combined graphical/textual rep-
resentation of the Enterprise Viewpoint concepts
applicable to IP topology management is shown
in Figure 8. The topological link is a link sup-
ported by a single trail in the server layer.A composition of enterprise objects formed to
meet a common objective is called a Community.
The community does not reference objects –
only the roles they play. The community speci-
fies the scope of a specific management task
being addressed. A community comprises a set
of roles, a set of actions and a set of policies to
satisfy the cooperative objective, or contract,
they play.An ordered series of actions combined to pro-
vide more comprehensive functions is called
anActivity.The service contract may be used for defining
the Service Level Specification(SLS) of a Ser-
vice Level Agreement(SLA), which expresses
the agreed functionality to be used in interac-
tions between the caller and the provider.In addition to capturing the functional require-
ments, the Enterprise Viewpoint also serves as a
roadmap towards the other viewpoints. Actions
in the Enterprise Viewpoint map to interface
operations in the Computational Viewpoint. The
client and provider roles map to computational
objects. Enterprise actions are normally con-
cerned with the manipulation (create, delete,
associate, etc.) of [G.805] network resource roles
like subnetworks, etc. Network resource roles
map to objects, attributes or relationships in the
Information Viewpoint.3.2.2 The Information Viewpoint
The static structure of a system is described in
terms of Information Objects, Attributes, Infor-
mation Relationshipsand Static Invariants
(static constraints). The information objects con-
stitute invariants, attributes and relationships.