Question

怎么分析这句话的语法结构

in all cases,someone has to act as a source of language data-an informant,who provide utterances for analysis and other kinds of information about the language。

Answer 1

In all cases, someone has to act as a source of language data––an informant, who provides utterances for analysis and other kinds of information about the language.

破折号前面的状语主语谓语没什么好说的吧，破折号后面的部分是a source of language data的同位语，who后面的定语从句修饰informant。

拆分成三句话的话就很清楚了:
In all cases, someone has to act as a source of language data.
Someone has to act as an informant.
The informant provides utterances for analysis and other kinds of information about the language.