Executable choreography: Difference between revisions

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'''Executable choreography''' represents a decentralized form of [[Service composability principle|service composition]], involving the cooperation of several individual entities. It is an improved form of [[service choreography]]. Executable choreographies can be intuitively seen as arbitrary complex workflows that get executed in systems belonging to multiple organisations or authorities.<ref>{{Cite journal|date=August 2015|title=Levels of Privacy for e-Health systems in the cloud era|url=http://www.math.md/files/csjm/v24-n3/v24-n3-(pp417-436).pdf|journal=24th International Conference on Information Systems Development|pages=243–253}}</ref>

Executable choreographies are actual codecodes created to encode system behavior from a global point of view. The behavior of the main entities in a system is given in a single program. Choreographies enhance the quality of software, as they behave like executable  blueprints of how communicating systems should behave and offer a concise view of the message flows enacted by a system.

== Executable vs. non-executable choreography ==

In almost all applications the business logic must be separated into different services. The [[Orchestration (computing)|orchestration]] represents the way that these services are organized and composed. The resulting service can be integrated hierarchically into another composition.<ref>{{Cite journal|date=March 2011|title=Choreography and Orchestration using Business Process Execution Language for SOA with Web Services|journal=IJCSI International Journal of Computer Science Issues|volume=8|issue=2|pages=224–232|viaurl=http://www.ijcsi.org/}}</ref>

[[Service choreography]] is a global description of the participating services, which is defined by the exchange of messages, rules of interaction and agreements between two or more endpoints. Choreography employs a decentralized approach for service composition.<ref>{{Cite web|url=https://stackoverflow.com/questions/4127241/orchestration-vs-choreography|title=Orchestration vs. Choreography}}</ref>

In industry, the concept of choreography is generally considered to be ''non-executable''. Standards, such as those proposed by the Web Services Choreography Description Language,<ref>{{Cite web|url=https://www.w3.org/TR/ws-cdl-10/|title=WSCDL Specification}}</ref> present the choreography as a more formal model to describe contracts between autonomous entities (generally distinct organisations) participating in a composition of services analyzed globally. From this perspective, the composition itself must be implemented centrally through the different orchestration mechanisms made available by companies: naive code composition or the use of specific orchestration languages and engines such as BPEL (Business Process Execution Language),<ref>{{Cite web|url=http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.pdf|title=WS-BPEL standard}}</ref> rule engines, etc.