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Static Definition

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