<!ELEMENT extension (provider*)>
<!ATTLIST extension
point CDATA #REQUIRED
id CDATA #IMPLIED
name CDATA #IMPLIED
>
<!ELEMENT provider (domain+ , nature* , subdomain* , property*)>
<!ATTLIST provider
class CDATA #REQUIRED
type CDATA #REQUIRED
>
<!ELEMENT nature (EMPTY)>
<!ATTLIST nature
id CDATA #REQUIRED
>
<!ELEMENT domain (EMPTY)>
<!ATTLIST domain
name CDATA #REQUIRED
>
<!ELEMENT subdomain (EMPTY)>
<!ATTLIST subdomain
name CDATA #REQUIRED
>
<!ELEMENT property (EMPTY)>
<!ATTLIST property
name CDATA #REQUIRED
>