英语大师帮帮忙！！！！！！

来源：百度知道 编辑：UC知道 时间：2024/06/23 08:18:15
The Contractor shall commence the Works immediately after having received the “Letter of Intent”from the owner/Owner’s representative and complete all the required works under this Contract Within one hundred and eight (108) calendar days from the date of taking over the building structure from civil contractor.
请问上面的句子里面为何要用having 和taking 请各位大师们讲的仔细并容易理解点噢

having received是receiving的完成形式having done，表示receive在commence这个动作之前就已经完成，如果是同时进行的两个动作就直接用receiving就可以了。如果你问为什么用receiving？因为这是after引导的现在分词状语，等于after they received ...，省略了主语。明白吗？
date of taking over 这个of是介词，介词后怎么能跟谓语即动词原型呢？介词后当然跟名词，(比如a cup of tea)这里的taking就是动名词，即动词加ing当名词用，修饰date.
容易吧？！