Neven MacEwan cogitated thusly:
> I don't think that writing it would be your problem - however
> using it might I assume that your OLE DB driver would return
> a set of Heirachal RecordSets (DataSets)
OLEDB provides some rather heavy abtractions that allow you to map you
base data into a the interfaces defined. One of the examples provided is
how you create a OLEDB provider from a list of email messages. So
presenting our ISAM files as an OLEDB provider is going to be a doddle.
All we do is provide the appropiate implementations for the row sets, and
the indexes and the rest of the OLEDB infrastrusture takes care of the
other stuff.
> and in a 3 teir solution these could be heterogenous -
> The problem being that most reporting tolls are aimed at RDMS.
> If not you could 'group' the 3rd tier objects and present them
> relationaly.
Its not a problem due to the design of OLEDB. If you have a full RDMS that
you provide interfaces to your own SQL parser and when invoked that
returns a interface to a row set, but if you have ISAM data you provide
the tables and indexes and OLEDB uses its own SQL engine to create the row
set output that is required.
OLEDB and ODBS are quite different in this way, and I'd recommend reading
one of the Inside OLEDB books to get a better knowledge of how the several
hundred OLDDB interfaces all work together.
> I was thinking last nite about Pauls comments - (The linetotal =
> price*quantity....) and would you not agree the the 'expression'
> related to this field is just another piece of Metadata
> In which case it fits neatly into your methodogy of driving the
> presentation from the field metadata
We have infact talked about this very issue. Paul has suggested that we
extend out basic metadata to include variable chukcs that could contain
expressions that would allow the dataengine to synthise fields as
required. As the expression language used would be our VB clone we could
do some fairly hairy stuff in the database engine, and as a side effect
could use the same expression at the UI level to do automatic field
updates as the user entered stuff.
Its all a bit extreme for the moment, but very fun stuff to think about.
Cheers, Max.
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