ICL Computer House Euston

21 June 79

ICL DMUG EUFSG(79) no. 5

Some definite progress towards agreement on what sort of conceptual view the projected end user facility should support was made at this meeting, and not before time. There was general agreement that entity modelling (as per ICL's Data Dictionary System) was the most effective technique currently available for mapping any end-user view onto whatever storage structures a particular DBMS employed (i.e. IDMS structures in practise, though theoretically any other DBMS could be used). Such techniques would result however in a global data model inappropriate to all but a few end-users. The group proposed that 'local' data models appropriate to various categories of end user should be supported, the mapping from each of these, via the global model, to the storage model to be the responsibility of the EUF proper. Such local models would not necessarily be simple subsets of the global model; in some cases relationships present in the global model might be suppressed, in others relationships not actually implemented in the storage model (because of e.g. volumetric considerations) might be present. I stressed the importance to University users of providing a relational local model, with some grudging support. It seemed probable that the DBS would/could be enhanced to provide support for local data models in this way, especially since construction of a global model for the DDS inevitably involved as a first step the construction of local models. The DDS subgroup would investigate.