Certified Ethical Hacker (CEH) v13 312-50v13 — Question 159

A certified ethical hacker is conducting a Whois footprinting activity on a specific domain. The individual is leveraging various tools such as Batch IP Converter and Whois Analyzer Pro to retrieve vital details but is unable to gather complete Whois information from the registrar for a particular set of data. As the hacker, what might be the probable data model being utilized by the domain's registrar for storing and looking up Whois information?