In 3.1 list item 2 we read "otherwise, the setting of the parameter is unspecified". I think "unspecified" here means "absent" - that is, the effect is that no value has been supplied for the parameter. This is different from "unspecified" which is used in at least one other place to mean "implementation-dependent".
Thank you for catching that inconsistency. If the working groups do not object, I will treat this editorially by making the following changes:
1. Replace item 2 in the numbered list in section 3.1 to read, "otherwise, the setting of the parameter is absent."
2. In the paragraph following the note in section 3.1, change the phrase, "any serialization parameters whose values remain unspecified after applying the mechanism" to "any serialization parameters whose values are absent after applying the mechanism"
This will be corrected in the next working draft of Serialization 3.0.