Useful resources 

 E-Book : The Great Guide to Learning Experience Platforms

 LRSDump

LRSDump is a xAPI tool to extract data from an LRS (Learning Record Store) in order to use them with BI (Business Intelligence) or Learning Analytics tools.

 xAPI 

 xAPI specifications

Specifications  from Advanced Distributed Learning (ADL) agency on the xAPI norm. Everything you need to implement xAPI in your organisation.