Office Open XML
L Annex L. (informative) Primer
L.2 Introduction to SpreadsheetML
L.2.2 Sheets
L.2.8.3.2.1 General Organization

L.2.8.3.2.1 General Organization

<metadata>
  <metadataTypes/>
  <metadataStrings/>
  <mdxMetadata/>
  <valueMetadata/>
</metadata>

There are four general collections in the metadata part:

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L.2.8.3.1.1 Function SummaryL.2.9.1 Feature Overview