[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Formulas in XML values
Formulas in XML values are a persistent concern for me for some days and xml-dev appears to be the best place to discuss this... From mathematical point of view, 35+7 and 42 are equals but human beings can interpret them differently. When a value has to be put in a field by an user, sometimes it's, in fact, the result of a basic computation and, when someone else has to verify the field value, the initial formula might help to understand. Excel users do that every day ! XML is a text notation so it's not disturbing to write 35+7 where 42 can be. But, schema languages should evaluate values before testing if they are valid or not. XPath should, at least, do the same or, better, be able to say that 15+6 multiplied by 2 is (15+6)*2. Students calculators can do that already, don't they ? There are interesting possibilities with such a notation improvement : numbers such as 1/3, pi, sqrt(2) would be written as what they are and not just in a limited amount of digits. Of course, a bunch of mathematical functions and constants should be named... I will probably implement some basic approach for this in my XForms implementation (XSLTForms : http://www.agencexml.com/xsltforms) because I already need it for setting values in XBRL documents. XSLTForms has its own XPath implementation and XML Schema validation, both written in Javascript, and some eval() calls at the right place might be all what is needed. Formulas will then be submitted and stored as ordinary values would be. If needed, I will design an XSLT stylesheet to resolve formulas into values (XSLTForms already has an XPath 1.0 expression parser written in XSLT 1.0 ...). Thank you for your remarks and suggestions. Best regards, Alain Couthures <agenceXML> http://www.agencexml.com Bordeaux, France Twitter account: AlainCouthures
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