[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Fwd: ANN: a portable data component -- length
Normal form isn't the only way to express data. It works for some scenarios but decidely not for others; take analytical databases, data marts, data warehouses, etc. For ages in the UK we had to have the price of loose fruit and vegetables on our shop shelves expressed in both price per imperial and price per metric weight. We still have shoes and clothes sold in UK and EU sizes. We don't give people one price and say "go work the other price out" or one size and say "go work out the other size; here is the conversion factor"... So we often produce price lists, I expect in XML, with multiple prices in mutliple currencies and we design database table deliberately with redundant information so that there is no need for extra time spent dereferencing information held in separate tables. I think Roger's examples hold well. On 09/04/2011, Liam R E Quin <liam@w3.org> wrote: > On Sat, 2011-04-09 at 11:10 -0400, Costello, Roger L. wrote: > >> Here is the altitude of an aircraft, expressed in both feet and meters: >> >> <altitude> >> <feet>12000</feet> >> <meters>3657.6</meters> >> </altitude> >> >> It is important that the two length values are consistent: > > The right way to mark this up in most cases is to store only one value > and convert as needed. > > See Normal Form in database theory: information should never be > duplicated. That way it can't get out of sync. > > So my answer is simply, "don't do this." > > Instead, e.g. > <measurement> > <name>altitude</name> > <value units="m">3657.6</value> > </measurement> > > (I'd use metric/SI units in a program as they're easier to deal with, > and mixed-based ambiguity like 3 feet 7 inches doesn't occur) > > Best, > > Liam > > -- > Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/ > Pictures from old books: http://www.fromoldbooks.org/ > Occasional blog: http://www.barefootliam.org/ > The barefoot typographer > > > > > _______________________________________________________________________ > > XML-DEV is a publicly archived, unmoderated list hosted by OASIS > to support XML implementation and development. To minimize > spam in the archives, you must subscribe before posting. > > [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ > Or unsubscribe: xml-dev-unsubscribe@lists.xml.org > subscribe: xml-dev-subscribe@lists.xml.org > List archive: http://lists.xml.org/archives/xml-dev/ > List Guidelines: http://www.oasis-open.org/maillists/guidelines.php > > -- ---- Stephen D Green
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