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Prof. Gio Wiederhold, Dr. Dorothea Beringer,

CHAIMS. Composing Autonomous Internet Services with CHAIMS. Prof. Gio Wiederhold, Dr. Dorothea Beringer,. Objective : Using and composing computational services offered by remote and autonomous megamodules.

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Prof. Gio Wiederhold, Dr. Dorothea Beringer,

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  1. CHAIMS Composing Autonomous Internet Services with CHAIMS Prof. Gio Wiederhold, Dr. Dorothea Beringer, Objective: Using and composing computational services offered by remote and autonomous megamodules. Approach: Develop and validate a composition-only language (CLAM), a protocol for large, distributed, heterogeneous and autonomous megamodules (CPAM), and a supporting system. CHAIMS

  2. Megamodule Providers wrap legacy megamodules writes CPAM compliant megamodules from scratch Wrapper Templates add information to CORBA / b CHAIMS Repository d e DCE / CPAM MEGA Modules a c Process - Providing Megamodules CHAIMS

  3. Composers write read CHAIMS Repository Megaprogram Megaprogram information written in CLAM generates CHAIMS Compiler Client Side Run Time compiled megaprograms Process - Composing Megamodules CHAIMS

  4. Client Side Run Time DCE / CPAM CORBA / d e b a c MEGA Modules Process - Running a Megaprogram located on the client server side CPAM Protocol on top of Distribution System (CORBA, RMI, …) located on several servers CHAIMS

  5. Advantages Advantages of using remote services: Knowledge • separation of concerns (provider - composer) • technical expertise • maintenance, newest algorithms Availability • pay per usage instead of pay per instance • lower barrier for clients to try out new modules • choice of several providers even at run-time Resources • access to computation intensive modules for everybody • minimal local resources possible Yet there are alsochallenges... CHAIMS

  6. Challenges - Services Computation intensive services: not free for a client • execution time of a service • transfer time for data • fees for services Autonomyof megamodules: • client has no controloveravailability of services and resources provided for services • heterogeneityconcerning languages, platforms as well as distribution protocols CHAIMS

  7. Characteristics CPAM • Asynchronous: • pre-invocation primitives • invocation and result extraction primitives • termination primitives • Cost-estimation • fee, execution time, data-volume of results • Presetting of input parameters • for cost estimation • avoiding repeated transmission of same parameters • Incremental result extraction • partial extraction of just those results that are ready • progressive extraction: repeated extraction of same result parameter with increasing accuracy • Progress monitoring • individual result parameters and progress of invocation CHAIMS

  8. Challenges - Composition Composer is non-technical domain expert: • expert in domain that uses these services, wants to focus on problem,e.g. scientist, assistant of a general • not knowledgeablein middleware system, not an experienced programmer Purely Compositional Language: • feasible? • strengths? • limits? ? CHAIMS

  9. Characteristics of CLAM • Hiding technical details • all protocol related details generated from few high-level primitives • Focus on composition: • no primitives for arithmetic ==> math megamodules • no primitives for input/output ==> general and problem-specific I/O megamodules • reduce complexity: not all facilities of a common language • Focus on asynchrony - exploiting strengths of CPAM • reduction of complexity of call-statements bysplitting up call-statement • parallelism by asynchrony in sequential program CHAIMS

  10. Upcoming Research Issues Applications, collaborations: • applying CHAIMS to a research system in bio-informatics • other collaborations? Composition: • automated optimization of a composition to exploit inherent parallelism of services, invocation scheduling at compile- as well as run-time • incremental composition, replacing compiler by interpreter with preprocessor • graphical composition Protocol: • using XML for CPAM primitives and CHAIMS repository • other distribution systems CHAIMS

  11. C H A I M S More Information... http://www-db.stanford.edu/CHAIMS beringer@db.stanford.edu gio@db.stanford.edu CHAIMS

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