The TEI scheme can only be used by customizing it.

Customizations are also expressed in the ODD language

For example:

<schemaSpec ident="myTEIlite">
<desc>This is TEI Lite with simplified heads</desc>
  <moduleRef name="teistructure"/>
  <moduleRef name="linking"/>
  <moduleRef name="core"/>
  <moduleRef name="teiheader"/>
  <elementSpec ident="head" mode="change">
    <content><rng:text/></content>
  </elementSpec>
</schemaSpec>

produces the schema for TEI Lite, with a slight change