Modular session types for objects

Simon J. Gay, Nils Gesbert, António Ravara, Vasco T. Vasconcelos

Research output: Contribution to journalArticle

6 Citations (Scopus)
2 Downloads (Pure)

Abstract

Session types allow communication protocols to be specified type-theoretically so that protocol implementations can be verified by static type checking. We extend previous work on session types for distributed object-oriented languages in three ways. (1) We attach a session type to a class definition, to specify the possible sequences of method calls. (2) We allow a session type (protocol) implementation to be modularized, i.e. partitioned into separately-callable methods. (3) We treat session-typed communication channels as objects, integrating their session types with the session types of classes. The result is an elegant unification of communication channels and their session types, distributed object-oriented programming, and a form of typestate supporting non-uniform objects, i.e. objects that dynamically change the set of available methods. We define syntax, operational semantics, a sound type system, and a sound and complete type checking algorithm for a small distributed class-based object-oriented language with structural subtyping. Static typing guarantees that both sequences of messages on channels, and sequences of method calls on objects, conform to type-theoretic specifications, thus ensuring type-safety. The language includes expected features of session types, such as delegation, and expected features of object-oriented programming, such as encapsulation of local state.

Original languageEnglish
Article number12
JournalLogical Methods In Computer Science
Volume11
Issue number4
DOIs
Publication statusPublished - 2015

Keywords

  • Non-uniform method availability
  • Object-oriented calculus
  • Session types
  • Typestate

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