[ibu]

And the same for content.opf.

<?xml version="1.0" encoding="utf-8"?>
<package 
version="3.0" 
unique-identifier="book-id" 
xmlns="http://www.idpf.org/2007/opf"
xmlns:opf="http://www.idpf.org/2007/opf"
xmlns:dc="http://purl.org/dc/elements/1.1/"
prefix="rendition: http://www.idpf.org/vocab/rendition/#">
  <metadata 
xmlns:opf="http://www.idpf.org/2007/opf"
xmlns:dc="http://purl.org/dc/elements/1.1/" 
xmlns:dcterms="http://purl.org/dc/terms/">
    <dc:title id="t1">Tanz der seligen Geister</dc:title>
    <meta refines="#t1" property="title-type">main</meta>
    <dc:creator id="create1">Alice Munro</dc:creator>
    <meta refines="#create1" scheme="marc:relators" property="role">aut</meta>
    <meta refines="#create1" property="file-as">Munro, Alice</meta>
    <dc:language>de-DE</dc:language>
    <dc:publisher>Dörlemann</dc:publisher>
    <dc:date>2012</dc:date>
    <dc:identifier id="book-id">urn:isbn:978-3-908778-02-8</dc:identifier>
    <meta name="Sigil version" content="0.9.7" />
    <meta property="dcterms:modified">2017-03-06T19:19:53Z</meta>
  </metadata>
  <manifest>
    <item id="ncx" href="toc.ncx" media-type="application/x-dtbncx+xml"/>
    <item id="title.xhtml" href="Text/title.xhtml" media-type="application/xhtml+xml"/>
    <item id="content.xhtml" href="Text/content.xhtml" media-type="application/xhtml+xml"/>
    <item id="about.xhtml" href="Text/about.xhtml" media-type="application/xhtml+xml"/>
    <item id="about.jpg" href="Images/about.jpg" media-type="image/jpeg"/>
    <item id="cover.jpg" href="Images/cover.jpg" media-type="image/jpeg"/>
    <item id="imprint.xhtml" href="Text/imprint.xhtml" media-type="application/xhtml+xml"/>
    <item id="default.css" href="Styles/default.css" media-type="text/css"/>
    <item id="navid" href="Text/nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
  </manifest>
  <spine toc="ncx">
    <itemref idref="title.xhtml"/>
    <itemref idref="content.xhtml"/>
    <itemref idref="about.xhtml"/>
    <itemref idref="imprint.xhtml"/>
    <itemref idref="navid"/>
  </spine>
</package>

I will edit the post later to comment the passages which are marked as bold.

Edit:

1 Are both, "xmlns" and "xmlns:opf" useful, even if in the metadata no "opf:*" exist?
The page "http://www.idpf.org/2007/opf" cannot be found, by the way.

2 Do we really need so many "systems" to declare metadata "opf:" "dc:" "dcterms:" and "rendition"?

3 Is <meta refines="#t1" property="title-type">main</meta> useful?

4 Is id="create1" in dc:creator useful?

...

I really hope, there is someone out there, with a deeper knowledge in those things than me, who created a minimal OPF for EPUB3.