<dict>
<key>CFBundlePackageType</key>
<string>FMWK</string>
<key>CFBundleShortVersionString</key>
<string>4.8</string>
But you answer your question, yes this format can be expressed with XML-Schema:
<xsd:element name="dict">
<xsd:complexType>
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:element name="key" type="xsd:string" />
<xsd:choice>
<xsd:element name="string" type="xsd:string" />
<xsd:element name="integer" type="xsd:integer" />
<!-- etc. -->
</xsd:choice>
</xsd:sequence>
</xsd:complexType>
</xsd:element> grammar {
start = Dict
Dict = element dict { DictItem* }
DictItem =
element key { text },
(element string { text } | element number { xsd:integer })
}