“…Scientific workflow systems have been used for accessing data from a variety of sources, including database systems (Altintas et al, 2004a), Grid systems (Altintas et al, 2003;Altintas et al, 2005;Deelman et al, 2005;Ludäscher et al, 2006;Taylor et al, 2007b), and Web Services (Altintas et al, 2004b). In addition, the Kepler workflow system has built-in tools for accessing heterogeneous environmental data by using details about data content and structure from metadata descriptions available in the Knowledge Network for Biocomplexity (KNB), a large-scale, distributed data system.…”