Educational data mining is an important tool that can be used to gather data and information about the student in digital context.. It can tell us how much knowledge a student has or does not have. It can help us to determine and prefict knowledge. It can help us to draw many inferences.. It's like surveillance on the student and it gives us all sorts of inputs to clearly assess the student on various criterion... 

We can get to know how much the student is engaging in learning online. It can provide us information on how much the student is serious about a particular subject or knowledge item

An educator can use the data provided by the data mining technique to plan lessons / assess students knowledge/ interest/ check his behaviour or check his presence.. A graph can show the students engagement online eg how much time does the student use to work on a topic for an assignment... 

The challenges that it poses are that there can be gaming by the student when he knows that he is being assessed continously online.. If he knows that his foot prints online are recorded and analysed to compile his  student assessment . . He is more likely to do gaming and use online tools etc to reach targets and fool his teachers