Hi,
In the feed at https://www.debian.org/security/dsa.rdf one can find statements such as
<item rdf:about="https://lists.debian.org/debian-security-announce/2026/msg00411.html">
<title>DSA-6496-2 nginx - regression update</title>
<link>https://lists.debian.org/debian-security-announce/2026/msg00411.html</link>
</item>
Generating the URL to the web archive for a DSA mail appears to be done at https://salsa.debian.org/webmaster-team/webwml/-/blob/HEAD/english/security/mk-dsa-dla-list#L230 and as you may see, the URLs are a suboptimal choice:
• the link is not semantic, but is tied to an implementation detail of how the archive service works right now
• the .html suffix effectively rules out a client wanting to use content negotiation to, for example, get a message/rfc822 original mail
• it's not apparent that the links are unique; they can't be cross-referenced even by a sleuth except for just resolving them
• using the web archive link in rdf:about is not great, because a URI would do; a canonical identifier for the mail or announcement itself, independent of any representation, would be more ideal
I've noticed many mailing list users and other Debian services use a better practice: using a mail's Message-ID to identity the mail itself, usually with the mid: URI scheme (RFC 2392), and also using the project's Message-ID resolver service to redirect to the mail archive, such as https://lists.debian.org/msgid-search/E1xBIPY-0000000DXRu-0qxr%40seger.debian.org/firsthit
It seems like you're creating more work for yourselves trying to parse dates and such; the archival URL using Debian's resolver service is expressed succinctly in the List-Archive header of almost any mail sent to a mailing list anyway (but as bug #1017636 points out this is actually wrong and a misappropriation of that header; we're supposed to be using Archived-At for that).
For rdf:about, or otherwise to have a unique identifier for the vulnerability announcement (independently of any particular rendering or representation), one can simply use the mid: URI scheme as in mid:E1xBIPY-0000000DXRu-0qxr%40seger.debian.org and this can even be useful for programs like Evolution, which are used for reading feeds as well as mail, and thus can understand the linkage between the two.