This paper studies a recently developed an approach to reasoning about mutable data structures, which uses an assertion language with spatial conjunction and implication connectives. We investigate computability and complexity properties of a subset of the language, which allows statements about the shape of pointer structures (such as "there is a link from x to y") to be made, but not statements about the data held in cells (such as "x is a prime number"). We show that validity, even for this restricted language, is not r.e., but that the quantifier-free sublanguage is decidable. We then consider the complexity of model checking and validity for several fragments.
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