+ <para><userinput>inductive i x y z: S ≝ k1:T1 | … | kn:Tn with i' : S' ≝ k1':T1' | … | km':Tm'</userinput></para>
+ <para>Declares a family of two mutually inductive types
+ <command>i</command> and <command>i'</command> whose types are
+ <command>S</command> and <command>S'</command>, which must be convertible
+ to sorts.</para>
+ <para>The constructors <command>ki</command> of type <command>Ti</command>
+ and <command>ki'</command> of type <command>Ti'</command> are also
+ simultaneously declared. The declared types <command>i</command> and
+ <command>i'</command> may occur in the types of the constructors, but
+ only in strongly positive positions according to the rules of the
+ calculus.</para>
+ <para>The whole family is parameterized over the arguments <command>x,y,z</command>.</para>
+ <para>If the keyword <command>coinductive</command> is used, the declared
+ types are considered mutually coinductive.</para>
+ <para>Elimination principles for the record are automatically generated
+ by Matita, if allowed by the typing rules of the calculus according to
+ the sort <command>S</command>. If generated,
+ they are named <command>i_ind</command>, <command>i_rec</command> and
+ <command>i_rect</command> according to the sort of their induction
+ predicate.</para>