How to extract the positions of employee from raw text
Have a look at this to see how a Knowledge Base can be built. I would say the best way is to build your own Knowledge Base based on your corpus if you have enough data.

The idea (simplified) for starting is to have patterns such as "NAME is POSITION" by seeing some of data. Through this you find many names and positions. Then you extract new patterns from them and scan whole data again. Do it until no new pattern shows up. Then you end up with lots of is-a relations which is what you need.

For extracting positions you may need sentence segmentation. Have a look at slide 56 onward to get an overview. 

PS: If you do not have enough data, you may crawl web and get texts and try to make your lexical databases. Target websites with more probability of having such a context.

Hope it helps. Good Luck!