IVOA Grid & Web Services: Asynchronous services

Contents

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Overview

Services are defined as being asynchronous when an operation on a web service starts some activity and returns immediately, leaving the activity running remotely. This asychronicity is useful in making a robust VO and is already used in some VO prototypes, e.g. Astrogrid's Common Execution Architecture (CEA). A conceptual proposal for managing the activities was drawn up and presented to IVOA in 2004. This was formalized into the Universal Worker Service (UWS) pattern.

Universal Worker Service

UWS proposes that a minimal interface supports job creation, polling of job status and retrieval. A fuller interface would also allowing requesting an estimate of the duration of a job amd restarting a failed job from its last checkpoint.

UWS-PA is an instantiation of the UWS pattern for parameterized applications (PA), i.e. applications whose input and output arguments can be expressed as a set of key-value pairs. CEA is an implementation of UWS-PA.

Specification

The latest version of the UWS proposal is v1.0 and is currently a recommendation.

Note from version 0.5 the source of the document is stored in the Volute GoogleCode Project

• ImplementingUWS-0.1.pdf: Lessons Learned from implementing UWS 0.3

Discussion

• Discussion page for enhancements to UWS

History

These are older versions of the UWS specification:

• UWS v0.1
• UWS v0.2
• UWS v0.3
• UWS-0.4
• UWS-0.5

Background reading

• Comparison of systems for contextual web services
• Common Execution Architecture (CEA)