The Grid is a complex, distributed and heterogeneous execution environment. Running applications requires the knowledge of many grid services: users need to discover the available resources and schedule the jobs onto them, essentially composing detailed application workflow descriptions by hand. This leaves users struggling with the complexity of the Grid and weighing which resources to use, where to run the computations, where to access the data etc. Thus there is a need to automate the workflow generation and execution process as much as possible. Pegasus: Planning for Execution in Grids  Maps from abstract to concrete workflow.  Isolates the user from many Grid details.  Automatically locates physical locations for both components (transformations) and data, via Globus RLS and the Transformation Catalog.  Finds appropriate resources to execute the components (via Globus MDS).  Interfaces with external site selectors.  Publishes newly derived data products.  Reuses existing data products where applicable.  Supports on demand staging of binary executables. Other Success Stories  Laser Interferometer Gravitational Wave Observatory (LIGO)  Montage  BLAST Genome Analysis and Database Update  ATLAS Monte Carlo data production  Sloan Digital Sky Survey galaxy cluster finding Planning the SCEC Pathways: Pegasus at work on the Grid People Involved: ISI : Ewa Deelman, Sridhar Gullapalli, Carl Kesselman, John McGee Gaurang Mehta, Gurmeet Singh, Mei-Hui Su, Karan Vahi SCEC: Vipin Gupta, Phil Maechling USC : Maureen Dougherty, Brian Mendenhall, Garrick Staples SCEC COMPOSITION PROCESS  CAT (Compositional Analysis Tool) an ontology based workflow composition tool or PCT (Pathway Composition Tool) generate the application workflows template (using ontologies and data types).  The Grid-Based Input Data selection component allows the user to select the input data necessary to populate the workflow template. The result in an abstract workflow that refers only to the logical application components and logical input data required for a pathway.  The DAX generator translates the abstract workflow to a corresponding XML description (DAX).  Pegasus takes in the DAX and generates the concrete workflow.  Concrete Workflow identifies the resources that are used to run on the grid and refers to the physical locations of input data.  Condor DAGMAN submits the workflow on the grid and tracks the execution of the workflow.  Successful execution generates the final hazard map for the region. A View of SCEC Composition Process Palm Springs Caltech Teragrid SCEC NCSA-Teragrid SDSC-Teragrid USC ANL-Teragrid PSC-Teragrid SCEC ResourcesTeragrid ResourcesOther Resources Testbed SCEC Workflow  Preparation job prepares input for Pathway 2 simulation.  Pathway 2 is Fortran based, wave propagation MPI code.  Pathway2PGV reads in binary output file generated by Pathway2, and converts it into hazard map that can be visualized.