OOXML mystery integer values

[Celly]

Hello!

This may seem odd but I'm getting into the nitty gritty of Open Office XML (OOXML) and have a question. I'm looking at one of the sheet xml files under xl/worksheets/. I see a lot of churn on these "s" attributes on cell elements. Here is an XML fragment:

<sheetData>
<row r="3" spans="1:16" x14ac:dyDescent="0.25">
<c r="E3" s="286" t="s">
<v>839</v>
</c>
</row>
</sheetData>

So this is cell E3 which has a value of 839. I get that part, but what is the s="286" element? These "s" elements move up or down in small increments when a workbook is saved, even if no changes are made. I could sift through the OOXML specification but I'm not intimately familiar with it. Any ideas?

 

[Celly]

I found it, it is a cell formatting index.

Office Open XML (OOXML) - Spreadsheets - Overview of Styles

That's a bummer, those index values move randomly every time the workbook is saved.

 

[Celly]

So for posterity, the main source of the churn is in the <cellXfs> collection in xl/styles.xml which is a table of cell formatting styles. This table appears to get reordered when you save, which has a ripple effect on all of the cells which reference these entries by index.

I'm testing Excel 2015, perhaps they've improved this behavior in subsequent releases?