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SNARL and SABLE: Enabling Interoperability with Other Grids
Karolina Sarnowska, University of Virginia
Overview: We present two web services that provide standards-based access to grid data registered in LCG File Catalogs. These services use gLite APIs to implement Open Grid Forum standards. The SNARL (Standards-based Naming for Accessing Resources in LFCs) service implements the Resource Namespace Service (RNS) specification while the SABLE (Standards-based Access to Bytes of LFC Entries) service implements the ByteIO specification. These services lay the foundation for interoperability with other grids. Analysis: LCG File Catalogs (LFCs) facilitate data management in gLite grids. An LFC is a file catalog that tracks the names and locations of grid files. Our work enables files registered in LFCs to be visible and readable to other Open Grid Forum (OGF) standards compliant grids via the RNS and ByteIO interfaces. The RNS specification describes a standard way for mapping named grid entities to unique WS-Addressing identifiers. Our SNARL service implements this OGF specification by creating a mapping for files registered in LFCs. The mapping is customized to handle both logical file names and replicas. The ByteIO specification describes a standard way of handling the transfer of data associated with grid entities. Our SABLE service implements this OGF specification by translating ByteIO operations into sets of gLite API calls that provide the requested data. Both SNARL and SABLE were implemented as Axis2/C web services. Impact: The driving force behind our work is to enable grid software interoperability. It is impossible for users of different grid infrastructures to collaborate directly using their own grid software unless the grids share common interfaces. Grids that implement the RNS and ByteIO specifications can understand what named entities exist in each other's grids as well as manipulate data represented by the named resources. Using our SNARL and SABLE web services, we have been able to successfully interoperate with Genesis II, another standards compliant grid. A Genesis II client was able to discover resources that existed in an LFC by sending RNS requests. The Genesis II client was then able to read the contents of the discovered files by sending ByteIO requests. Our work is the first to demonstrate that both the RNS and the ByteIO OGF specifications can be implemented for a grid system that developed separately from them. Conclusions and Future Work: The SNARL and SABLE web services extend the gLite middleware to include the first implementations of the OGF RNS and ByteIO specifications for EGEE. These interfaces enable standards-based access to grid files registered in LFCs. Next, we plan on enhancing the SNARL and SABLE web services with security. To help surmount the difficulties involved with the incorporation of security mechanisms, we plan on utilizing OGF security standards.
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