Each pertinent standard should be cited by version number, but also flagged as to its errata status when relevant. The version values mentioned above are numeric so that inequality tests may be applied. The main spec version should always be present, and should be set to a default if the test is really about some other associated spec. In other words, when dealing with two or more specifications, any test that is essentially a pure test of one specification should assume the base version of the others. Any test that is essentially about a newer spec, should specify the lowest practical level of the other specifications, which may have to be higher than the base level if modifications are necessary for the newer facility to work at all.
The version-drop allows intermixing of tests that become obsolete for newer versions of a standard. It indicates that the test case is no longer pertinent as of that version.
Errata are independent of newer spec versions, and multiple errata could be issued per version. Our flexible approach is to have a spec-citation attribute named "errata-add" that contains a date or numeric value (0 for the base document) like the E-number in the XSLT errata; "errata-drop" is numerically larger and indicates that the test case is no longer pertinent as of that errata version. Not all Working Groups are numbering their errata, so there is some safety in using dates. Date attributes should be in ISO-8601 format, which will sort numerically. The add and drop levels allow a test case to be marked as being relevant for errata that later get further clarified. The errata-drop must always be numerically greater than errata-add, and likewise for the dates. Errata parameters need only be specified where the test applies to a specific erratum, or the base document only, because they are used for filtering. In other words, a test case should not have any errata designations unless there is at least one erratum that could make the test excludable for processors that came either before or after that erratum.