based在下面这两句话中的词性是什么，分析一下结构？

We主 do not report谓 organic keywords宾 or traffic宾 which is an estimation based solely on the keywords data we have for a site UR metrics as they are all backlinks定语从句

定语从句which引导词主语 is系动词 an estimation表语 based solely on the keywords data we have for a site UR metrics as they are all backlinks定语

based solely on the keywords data 过去分词短语作定语，修饰an estimation

相当于which is based solely on...