Detailed Instructions: You will be given a context, a subject and a relation. Your task is to generate a question based on the subject and relation. The generated question should include the given subject. Try to use a minimum number of words that are not present in either context, subject or relation while generating question.
Problem:Context : The first XPL0 compiler was written in ALGOL. 
Subject : XPL0 
Relation : based on
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Which is the basis of XPL0?