1. Legion Worldwide virtual computer

2. About Legion Made in University of Virginia Object-based metasystems software project middleware that connects computer resources into a one big virtual computer Hides the complexity from user Supports different OS/hardware/languages No centralized structure -> highly scalable

3. Legion design objects Site autonomy Scalability Easy to use, seamless computational environment High performance with parallelism Single, persistent name space Security for users and resource owners Management and exploitation of resource heterogeneity

4. Design objects continued Multiple language support Fault tolerance Extensible core

5. Design restrictions Must run on existing OS:s Must run on existing interconnection networks Legion can’t be required to run as ”root”

6. Architecture of Legion Everything is an object Classes define and manage instances Users can create their own classes Core objects implement common services

7. Core objects Host objects Vault objects Implementation objects Binding agents Context objects Can be replaced for special needs for special needs

8. Security solutions Everything runs in user space, no superuser present All objects are subject to local access policies MayI? access control framework Public key encryption for inter-object communication

9. Resource management Resources reserved by negotiation with each provider Computational and storage resources can currently be reserved Three major components for resource management Collection: manages resource state information Scheduler: maps requests to resources Enactor: implements the computed schedule

10. Parallelisation emulation of MPI and PVM MPL (Mentat Programming Language) or BFS (Basic Fortran Support) object wrapping directly exporting run-time libraries