Dear XLIFF experts, I was looking at some issues related to <sc>/<ec> handling and reading XLIFF 2.1 specification closely. The attribute isolated MUST be set to yes if and only if the <ec> element corresponding to this start marker is not in the same <unit> , and set to no otherwise. If there are <sc> and corresponding <ec> are in a same <unit>, then it's NOT isolated. It looks this statement is very straight forward, but it becomes ambiguous if this constraint also applies to <target>. The example in this section is below ? <unit id="1"> <segment> <source><sc id="1" type="fmt" subType="xlf:b"/> First sentence. </source> </segment> <segment> <source>Second sentence.<ec startRef="1" type="fmt" subType="xlf:b"/></source> </segment> </unit> But the spec is not clear about the case when only one segment has translation available. <unit id="1"> <segment state="translated"> <source><sc id="1" type="fmt" subType="xlf:b"/> First sentence. </source> <target><sc id="1" type="fmt" subtype="xlf:b"/> ????? </target> </segment> <segment> <source>Second sentence.<ec startRef="1" type="fmt" subType="xlf:b"/></source> </segment> </unit> Does above valid? When translation memory is managed at each parsed segment level, then this could happen. I think the constraints should only apply to <source> part, otherwise, a single unit cannot be partially translated. BTW, I wanted to check if the XLIFF is validated with the XLIFF Validation Service . I found the example in the XLIFF specification was invalidated with the message: Reason: <sc> element without matching <ec> in <source>. Rodolfo, you might want to look at this. -Yoshito