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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