Sessions and Pipelines for Structured Service Programming

Abstract

Abstract. Service-oriented computing is calling for novel computational models and languages with primitives for client-server interaction, orchestration and unexpected events handling. We present CaSPiS, a process calculus where the notions of session and pipelining play a central role. Sessions are two-sided and can be equipped with protocols executed by each side. Pipelining permits orchestrating the flow of data produced by different sessions. The calculus is also equipped with operators for handling (unexpected) termination of the partner's side of a session. Several examples are presented to provide evidence for the flexibility of the chosen set of primitives. Our main result shows that in CaSPiS it is possible to program a "graceful termination" of nested sessions, which guarantees that no session is forced to hang forever after the loss of its partner.

Orchestrating Tuple-Based Languages

“…From the theoretical point of view, the formalisms closest to ours are Orc and Klaim. In fact, to define Korc, we have chosen them as representative of the broader classes of orchestration calculi (as, e.g., [28,10,23,11,7]) and coordination calculi for network-aware and mobility programming (as, e.g., [21,24,12,39]). Relatively to these calculi, Korc does not provide new primitives, but it permits experimenting and reasoning on a novel programming paradigm combining orchestration and coordination operators.…”

“…Among the several proposals, we want to mention below those designed for programming distributed networked applications. JCaSPiS [3] is a Java implementation of the service-oriented calculus CaSPiS [7] that, as well as Korc, takes inspiration by Orc (in particular, for the use of the sequential composition operator, called pipeline, over value streams). CaSPiS's implementation is based on the generic Java framework IMC [2] that provides recurrent mechanisms for network applications and, hence, can be used as a middleware for the implementation of different process calculi.…”

“…Among the many proposed formalisms (see, e.g., [28,8,10,23,11,7]), we will focus on Orc [31,40], a task orchestration language with applications in workflow, business process management, and web service orchestration. Orc is the This work has been partially sponsored by the EU project ASCENS, 257414. result of a tension between simplicity and expressiveness, and its primitives, differently from most the formalisms mentioned above, focus on orchestration rather than on communication.…”

Inference of Global Progress Properties for Dynamically Interleaved Multiparty Sessions

“…In G a , line (1) denotes Alice sending a string value to Seller. Line (2) says that Seller multicasts the same integer value to Alice and Bob and line (3) says that Alice sends an integer to Bob. In lines (4)(5)(6) Bob sends either ok or quit to Seller and Alice.…”

“…The service name a is used for initiating sessions corresponding to the global type G a . Seller initiates a three party session by means of the session request operation a [3](y), where the index 3 identifies Seller. Since 3 is also the overall number of participants in this session, a occurs with an over-bar.…”