A Cofinal Family of Equivalence Relations and Borel Ideals Generating Them

An increasing $\omega _1$-sequence of Borel equivalence relations on a Polish space that is cofinal (in the sense of Borel reducibility) in the family of all Borel equivalence relations is defined as a development of Rosendal's construction. It is proved that equivalence relations from this sequence are generated by explicitly defined Borel ideals.