Deformation Theory of Pseudogrou p Structure s 5,
deformations) h e r e . What we shall do is to show how thes e problem s reduce
to a clas s of problem s in partia l differential equations. We shall indicate
(in som e cases ) when thes e problem s have been solved and state som e
As was mentioned above, we will impos e som e additional r e s t r i c -
tions on our pseudogroups to mak e the m amenabl e to analysis . It is easies t
to state thes e restriction s in t e r m s of the language of jet s which we shall
briefly recal l in the next section.