Download National e-Science Centre Temporal Database in Depth: Time and the Data

National
e-Science
Centre
Temporal Database in Depth: Time and the Data
Warehouse
e-Science Institute 3rd November 2005
A special one day meeting on the subject of temporal databases was held on Thursday 3rd
November 2005, at the National e-Science Centre in Edinburgh. The meeting was addressed by
Chris Date, the well known exponent of the relational database, who presented a detailed and
theoretical seminar on the issues affecting the design of temporal databases. In the afternoon Rob
Squire of Oracle Corporation UK spoke on the blue sky research work that he has been doing on
temporal databases and managing time varying data.
Chris Date’s seminar was closely based on the work that he has already published in “Temporal
Data & the Relational Model “ by himself, Hugh Darwen and Nikos Lorentzos. The point was
made that temporal databases are becoming of increasing importance. Cheap disk storage and
ever more powerful processors enable the assimilation of both current and historical data, and of
course their link is the temporal component. But two approaches have already emerged in
handling this type of data. On the one hand are the specialised systems optimised for temporal
data (‘the bad guys’, according to Date), and on the other, those systems which are based firmly
on the existing relational principles (‘the good guys’). Needless to say, Date falls firmly into the
latter category.
The subject is a complex one, and Date explored it in his characteristically thorough and detailed
fashion. He spent time defining intervals, temporal constraints, the expand and collapse operators,
and the pack and unpack operators. Sixth Normal Form was introduced as an important
component, with the suggestion that this really was perhaps the last normal form that would need
to be defined. His temporal model was defined by nine requirements. Some twelve queries were
also introduced as being the means of validating the true temporal functionality of a temporal
database. But there was so much more – the interested reader should refer to the text by Date et al
referred to above.
In the afternoon, Rob Squire presented the results of some of the research into temporal databases
and managing time varying data that he has been doing for Oracle. After outlining his approach,
he then proceeded to demonstrate a succession of temporal queries, including some of the twelve
that Date had already identified. What was interesting here was that the approach taken by Squire
was firmly based on the relational model (thereby earning the sobriquet ‘good guy’), and was also
based on standard (Oracle) SQL, without the use of any extensions or special functions, including
any of those already discussed by Date. There was unfortunately insufficient time to go into the
details of the architecture, but Squire noted that he saw no difficulty in solving all twelve of the
test queries that Date had introduced as the criteria for a temporal database.
This was a fascinating and stimulating glimpse into what is a complex aspect of database design.
It is very likely that a follow-up event may be held, most particularly to see how the solution
proposed by Squire can handle very large data volumes. As the initiator of the event in the first
place, I must extend special thanks to the e-Science Centre who very kindly provided the
hospitality of their premises, including the excellent refreshments, and to Oracle Corporation
Scotland, who enabled the whole event to happen by sponsoring the meeting. Finally, I must
express my gratitude to Chris Date and Rob Squire for speaking, and to all who attended in
making this such an enjoyable meeting.
Peter Robson