Hello Thomas, On 11-10-05 4:41 PM, "Arek Kasprzyk" <[email protected]<mailto:[email protected]>> wrote: The target schema will be a query optimized version of the source schema. The target schema complies with the reverse star spec so it will always be different from the source. However, the schemas and SQL against them are functionally equivalent so they will return the same data. As Arek explained it here, there is no need to worry about how the data is materialized. Queries on a materialized mart will return the same results as queries on a virtual mart, but the former are faster due to the nature of how query engines work. Data "denormalization" into reverse star- or snowflake-schema is quite common when handling read-only databases. The nice thing about BioMart is the fact that it does the data denormalization for you — so you do not really need to know what happens behind the curtains in order to benefit from the resulting query optimizations.
Anyway, there is currently a whole bunch of BioMart papers that have been published in Database Journal, which might help you to get a bit more into the details how the system works: http://database.oxfordjournals.org/search?submit=yes&fulltext=biomart Joachim Joachim Baran, PhD Database Programmer/Technical Analyst, Informatics and Bio-computing Ontario Institute for Cancer Research MaRS Centre, South Tower 101 College Street, Suite 800 Toronto, Ontario, Canada M5G 0A3 Tel: 647-258-4319 Toll-free: 1-866-678-6427 www.oicr.on.ca This message and any attachments may contain confidential and/or privileged information for the sole use of the intended recipient. Any review or distribution by anyone other than the person for whom it was originally intended is strictly prohibited. If you have received this message in error, please contact the sender and delete all copies. Opinions, conclusions or other information contained in this message may not be that of the organization.
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