MetaFrame in Practice: Design of Intelligent Network Services - Correct System Design: Recent Insights and Advances - page 384

Fig. 3. Fragment of the SIB Taxonomy
Formally, taxonomies are labelled directed acyclic graphs. In this case, sinks
represent concrete SIBs, the atomic entities of the taxonomy, and intermediate
nodes represent groups, i.e., sets of SIBs with a particular prole. Edges reflect an
is-a relation between their target and source node. Figure 3 shows a fragment of
the SIB taxonomy as it is presented by the hypertext system. Here pin-change
and check-pin are both sinks, and represent SIBs of the group authorization .
The development of adequate taxonomies is a crucial part of the domain
modelling as it provides users with an application-specic handle to the avail-
able BBs. Thus, in general, taxonomies must be extended not only when new
functionalities are integrated, but also whenever one wants to establish a new
`application-specic view' on the so far integrated functionalities: the same BB
may well be taxonomically classied completely dierently in dierent appli-
cation domains. E.g. establishing a network connection is quite central in the
area of telecommunication, whereas it may be regarded just as a `commodity' in
another application area.
In this project the taxonomies were dened freely, on top of an SNI-specic
set of SIBs implementing the IN-functionality dened in the ITU standard.