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A (deliberate) restriction of the
noticeboard system is that a noticeboard is static in structure. Its
structure must be defined before any values are put into it and once the
definition is complete no more items can be created. There are a set of
routines called NBS_DEFINE_* and NBS_*_DEFINITION
which allow definition
of noticeboard contents, saving definitions to and restoring them from
file (the initial state of a noticeboard is that all items have zero
length values). Only once the definition phase is complete can the
NBS_PUT_* and NBS_GET_* routines be used.
The initial reason for this was efficiency. However it is not in fact
particularly difficult to allow new items to created on the fly without
compromising efficiency and this restriction should be seen more as a way
of preventing the noticeboard routines from being used for purposes for
which they were not designed and for which better tools (such as
HDS) exist. Note that this ``static'' restriction refers only to
the creation of
items in the noticeboard. It is always possible to change item shapes and
values.
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NBS The Noticeboard System
Starlink User Note 77
D.J. Allan
11 September 1995
E-mail:ussc@star.rl.ac.uk