  Separation logic and its variants can describe various properties on pointer
programs. However, when it comes to properties on sequences, one may find it
hard to formalize. To deal with properties on variable-length sequences and
multilevel data structures, we propose sequence-heap separation logic which
integrates sequences into logical reasoning on heap-manipulated programs.
Quantifiers over sequence variables and singleton heap storing sequence
(sequence singleton heap) are new members in our logic. Further, we study the
satisfiability problem of two fragments. The propositional fragment of
sequence-heap separation logic is decidable, and the fragment with 2
alternations on program variables and 1 alternation on sequence variables is
undecidable. In addition, we explore boundaries between decidable and
undecidable fragments of the logic with prenex normal form.
