2.1.653 Part 4 Section 220.127.116.11, formula1 (Formula 1)
a. The standard states that the contents of this element are an extension on the ST_Formula simple type.
Excel requires the contents of this element for a data validation formula, as defined in Data Validation Formulas (§18.104.22.168.3, Data Validation Formulas).
b. The standard makes no mention of an xml:space attribute.
Excel uses this attribute to specify, using the W3C space preservation rules, how white space should be handled for the element's contents; its allowed values are defined by the XML 1.0 specification.