An open source application framework for astronomical imaging pipelines

The LSST Data Management System is built on an open source software framework that has middleware and application layers. The middleware layer provides capabilities to construct, configure, and manage pipelines on clusters of processing nodes, and to manage the data the pipelines consume and produce. It is not in any way specific to astronomical applications. The complementary application layer provides the building blocks for constructing pipelines that process astronomical data, both in image and catalog forms. The application layer does not directly depend upon the LSST middleware, and can readily be used with other middleware implementations. Both layers have object oriented designs that make the creation of more specialized capabilities relatively easy through class inheritance. This paper outlines the structure of the LSST application framework and explores its usefulness for constructing pipelines outside of the LSST context, two examples of which are discussed. The classes that the framework provides are related within a domain model that is applicable to any astronomical pipeline that processes imaging data. Specifically modeled are mosaic imaging sensors; the images from these sensors and the transformations that result as they are processed from raw sensor readouts to final calibrated science products; and the wide variety of catalogs that are produced by detecting and measuring astronomical objects in a stream of such images. The classes are implemented in C++ with Python bindings provided so that pipelines can be constructed in any desired mixture of C++ and Python.