Each worksheet in a spreadsheet is represented by an XML document with a root element named {{tag|worksheet}} in the {{LinkBlue|<nowiki>http://schemas.openxmlformats.org/spreadsheetml/2006/main</nowiki>}} Namespace.
The representation of date and time values in SpreadsheetML has attracted some criticism. ECMA-376 1st edition does not conform to ISO 8601:2004 "Representation of Dates and Times". It requires that implementations replicate a [[Lotus 1-2-3]]<ref>{{ cite web | url = http://www.exceluser.com/explore/earlydates.htm | title = How to Work With Dates Before 1900 in Excel | first = Charley | last = Kyd | date = October 2006 | work = ExcelUser | access-date = 2009-09-16 }}</ref> bug that erroneously treats 1900 as a leap year. Products complying with ECMA-376 would be required to use the WEEKDAY() spreadsheet function, and therefore assign incorrect dates to some days of the week, and also miscalculate the number of days between certain dates.<ref name="The Contradictory Nature of OOXML">{{ cite web | url=http://www.consortiuminfo.org/standardsblog/article.php?story=20070117145745854 | title=The Contradictory Nature of OOXML | publisher=ConsortiumInfo.org}}</ref> ECMA-376 2nd edition (ISO/IEC 29500) allows the use of 8601:2004 "Representation of Dates and Times" in addition to the Lotus 1-2-3 bug-compatible form.<ref>{{ cite web | url = http://www.ecma-international.org/publications/standards/Ecma-376.htm | title = ECMA-376 2nd edition Part 1 (3. Normative references) | publisher = Ecma-international.org | access-date = 2009-09-16}}</ref><ref>{{ cite web | url = http://www.ecma-international.org/news/TC45_current_work/New%20set%20of%20proposed%20dispositions%20posted.htm | title = New set of proposed dispositions posted, including more positive changes to the Ecma Office Open XML formats – Dispositions now proposed for more than half of National Bodies' comments | publisher = Ecma-international.org | date = 2007-12-11 | access-date = 2009-09-16}}</ref>
=== Office MathML (OMML) ===
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DrawingML is unrelated to the other [[vector graphics]] formats such as [[Scalable Vector Graphics|SVG]]. These can be converted to DrawingML to include natively in an Office Open XML document. This is a different approach to that of the [[OpenDocument]] format, which uses a subset of SVG, and includes vector graphics as separate files.
A DrawingML graphic's dimensions are specified in English Metric Units (EMUs). It is so called because it allows an exact common representation of dimensions originally in either English or Metric units -- definedunits—defined as 1/360,000 of a [[centimeter]], and thus there are 914,400 EMUs per [[inch]], and 12,700 EMUs per [[point (typography)|point]], to prevent round-off in calculations. [[Rick Jelliffe]] favors EMUs as a rational solution to a particular set of design criteria.<ref>{{ cite web|date=April 16, 2007 |author= Rick Jelliffe in Technical | url = http://www.oreillynet.com/xml/blog/2007/04/what_is_an_emu.html | title = Why EMUs? - O'Reilly XML Blog | publisher = Oreillynet.com | access-date = 2009-05-19}}</ref>
Some have criticised the use of DrawingML (and the transitional-use-only [[Vector Markup Language|VML]]) instead of [[World Wide Web Consortium|W3C]] recommendation [[Scalable Vector Graphics|SVG]].<ref>{{ cite web | url=http://reddevnews.com/features/article.aspx?editorialsid=2356 | title= The X Factor | publisher=reddevnews.com |date=October 2007 }}</ref> VML did not become a W3C recommendation.<ref>{{ cite web | url = http://www.w3.org/TR/NOTE-VML | title = VML — the Vector Markup Language | publisher = W3.org | date = 1998-05-13 | access-date = 2009-05-19 }}</ref>