https://tools.ietf.org/html/rfc4035#section-2.4

2.4.  Including DS RRs in a Zone

   The DS resource record establishes authentication chains between DNS
   zones.  A DS RRset SHOULD be present at a delegation point when the
   child zone is signed.  The DS RRset MAY contain multiple records,each referencing a public key in the child zone used to verify the
   RRSIGs in that zone.  All DS RRsets in a zone MUST be signed,and DS
   RRsets MUST NOT appear at a zone's apex.

   A DS RR SHOULD point to a DNSKEY RR that is present in the child's
   apex DNSKEY RRset,and the child's apex DNSKEY RRset SHOULD be signed
   by the corresponding private key.  DS RRs that fail to meet these
   conditions are not useful for validation,but because the DS RR and
   its corresponding DNSKEY RR are in different zones,and because the
   DNS is only loosely consistent,temporary mismatches can occur.

这确定了允许多个DS RR,并且每个RR应该由相应的DNSKEY RR签名.虽然遇到孤立DS RR时的确切行为并未明确,但已确定不匹配可以并且确实发生,并且是可以预期的.

最后,人们可以从承认中收集到DNS只是松散地一致,相反的期望是错误的.因此,人们当然可以编写一个验证器实现,将该区域视为虚假,但这样做并不是非常有用.在一天结束时,要考虑的主要因素是区域是否已签名,以及DS RRset和签名的RR之间是否存在有效的加密路径.

https://tools.ietf.org/html/rfc6840#section-5.11

5.11.  Mandatory Algorithm Rules

   The last paragraph of Section 2.2 of [RFC4035] includes rules
   describing which algorithms must be used to sign a zone.  Since these
   rules have been confusing,they are restated using different language
   here:

      The DS RRset and DNSKEY RRset are used to signal which algorithms
      are used to sign a zone.  The presence of an algorithm in either a
      zone's DS or DNSKEY RRset signals that that algorithm is used to
      sign the entire zone.

      A signed zone MUST include a DNSKEY for each algorithm present in
      the zone's DS RRset and expected trust anchors for the zone.  The
      zone MUST also be signed with each algorithm (though not each key)
      present in the DNSKEY RRset.  It is possible to add algorithms at
      the DNSKEY that aren't in the DS record,but not vice versa.  If
      more than one key of the same algorithm is in the DNSKEY RRset,it
      is sufficient to sign each RRset with any subset of these DNSKEYs.
      It is acceptable to sign some RRsets with one subset of keys (or
      key) and other RRsets with a different subset,so long as at least
      one DNSKEY of each algorithm is used to sign each RRset.
      Likewise,if there are DS records for multiple keys of the same
      algorithm,any subset of those may appear in the DNSKEY RRset.

   This requirement applies to servers,not validators.  Validators
   SHOULD accept any single valid path.  They SHOULD NOT insist that all
   algorithms signaled in the DS RRset work,and they MUST NOT insist
   that all algorithms signaled in the DNSKEY RRset work.  A validator
   MAY have a configuration option to perform a signature completeness
   test to support troubleshooting.

整体情况在这里变得更加清晰;验证者不应该管理DS和DNSKEY的所有可能的排列.最重要的细节是是否存在有效路径.