What's the difference between <c t="str"> and <c><is> in Office Open XML?

Question

What's the difference between these two Office Open XML fragments?

<c r="A2" t="str">
  <v>btyler</v>
</c>

and

<c r="B2">
  <is><t>btyler</t></is>
</c>    

note: The second sample I created manually based on the spec, the first is from an actual Excel workbook.

Both seem valid and pretty much identical according to the spec, so I'm wondering why there is t="str" when <is> seemingly does the same thing. When does Excel choose to use one over the other?

Answer 1

According to the documentation at 18.18.11 ST_CellType:

str (String) Cell containing a formula string.

So you would only use your first example if a formula was in the <x:v> element.

The second one is used for inline strings and the <x:c> element should have a t attribute of 'inlineStr'. This will just be rich text that will be outputted and not stored in the sharedstring table.

So your first one would be valid like this:

<x:c r="C6" s="1" vm="15" t="str">
   <x:f>CUBEVALUE("xlextdat9 Adventure Works",C$5,$A6)</x:f>
   <x:v>2838512.355</x:v>
</x:c>

Your second one would be valid like this:

<x:c r="B2" t="inlineStr">
   <is><t>btyler</t></is>
</c>