联合提交的域名边界构成是如何确定的？当新的注册人加入联合提交时，牵头注册人是否有义务更新边界构成？

联合提交的域名边界构成是如何确定的？当新的注册人加入联合提交时，牵头注册人是否有义务更新边界构成？

How is a boundary composition established within a joint submission? Is the lead registrant obliged to update the boundary composition when a new registrant enters the joint submission?

REACH 要求联合提交的所有成员就物质同一性进行讨论，并确定联合提交所涵盖物质的边界。所有成分和定义边界成分的物质识别参数必须经集体商定，并在物质身份档案 (SIP) 中清晰记录（参见问答 1447）。根据新的潜在注册人的要求，如果所有共同注册人同意联合提交的数据也适用于该新潜在注册人生产或进口的物质，则可能需要完善边界成分。如果不是，牵头注册人没有义务修改现有的边界成分。无论如何，所有各方都需要确保所应用的标准是透明的，并且所收集/生成的相关附件 VII-XI 数据明显涵盖联合提交中所有商定的成分。

REACH requires that all members of a joint submission engage in discussions on substance sameness and establish the boundaries of the substance covered by the joint submission. All compositions and substance identification parameters defining the boundary composition must be collectively agreed and clearly documented in the substance identity profile (SIP) (see Q&A 1447). Following the request of a new potential registrant, the boundary composition may need to be refined if all co-registrants agree that the jointly-submitted data is also relevant for the substance manufactured or imported by this new potential registrant. If not, the lead registrant is not obliged to amend the existing boundary composition. In any case, all parties would need to ensure that the criteria applied are transparent and that the relevant Annex VII-XI data collected/ generated demonstrably covers all agreed compositions within the joint submission.