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A hierarchical coordination language for reliable real-time tasks
Arkadeb Ghosal

Citation
Arkadeb Ghosal. "A hierarchical coordination language for reliable real-time tasks". Talk or presentation, 22, January, 2008.

Abstract
Complex requirements, time-to-market pressure and regulatory constraints have made the designing of embedded systems extremely challenging. This is evident by the increase in effort and expenditure for design of safety-driven real-time control-dominated applications like automotive and avionic controllers. Design processes are often challenged by lack of proper programming tools for specifying and verifying critical requirements (e.g. timing and reliability) of such applications. Platform based design, an approach for designing embedded systems, addresses the above concerns by separating requirement from architecture. The requirement specifies the intended behavior of an application while the architecture specifies the guarantees (e.g. execution speed, failure rate etc). An implementation, a mapping of the requirement on the architecture, is then analyzed for correctness. The orthogonalization of concerns makes the specification and analyses simpler. An effective use of such design methodology has been proposed in Logical Execution Time (LET) model of real-time tasks. The model separates the timing requirements (specified by release and termination instances of a task) from the architecture guarantees (specified by worst-case-execution time of the task). This dissertation proposes a coordination language, Hierarchical Timing Language (HTL), that captures the timing and reliability requirements of real-time applications. An implementation of the program on an architecture is then analyzed to check whether desired timing and reliability requirements are met or not. The core framework extends the LET model by accounting for reliability and refinement. The reliability model separates the reliability requirements of tasks from the reliability guarantees of the architecture. The requirement expresses the desired long-term reliability while the architecture provides a short-term reliability guarantee (e.g.~failure rate for each iteration). The analysis checks if the short-term guarantee ensures the desired long-term reliability. The refinement model allows replacing a task by another task during program execution. Refinement preserves schedulability and reliability, i.e., if a refined task is schedulable and reliable for an implementation, then the refining task is also schedulable and reliable for the implementation. Refinement helps in concise specification without overloading analysis. Along with the formal HTL model and subsequent analyses (both with and without refinement), the work presents a compiler that accepts an HTL program. The compiler checks composition and refinement constraints, performs schedulability and reliability analyses, and generates code for replicated, distributed implementation of the HTL program on a virtual machine. Three real-time controllers, one each from automatic control, automotive control and avionic control, are used to illustrate the steps in modeling and analyzing HTL programs.

Electronic downloads

Citation formats  
  • HTML
    Arkadeb Ghosal. <a
    href="http://chess.eecs.berkeley.edu/pubs/400.html"
    ><i>A hierarchical coordination language for
    reliable real-time tasks</i></a>, Talk or
    presentation,  22, January, 2008.
  • Plain text
    Arkadeb Ghosal. "A hierarchical coordination language
    for reliable real-time tasks". Talk or presentation, 
    22, January, 2008.
  • BibTeX
    @presentation{Ghosal08_HierarchicalCoordinationLanguageForReliableRealtime,
        author = {Arkadeb Ghosal},
        title = {A hierarchical coordination language for reliable
                  real-time tasks},
        day = {22},
        month = {January},
        year = {2008},
        abstract = {Complex requirements, time-to-market pressure and
                  regulatory constraints have made the designing of
                  embedded systems extremely challenging. This is
                  evident by the increase in effort and expenditure
                  for design of safety-driven real-time
                  control-dominated applications like automotive and
                  avionic controllers. Design processes are often
                  challenged by lack of proper programming tools for
                  specifying and verifying critical requirements
                  (e.g. timing and reliability) of such
                  applications. Platform based design, an approach
                  for designing embedded systems, addresses the
                  above concerns by separating requirement from
                  architecture. The requirement specifies the
                  intended behavior of an application while the
                  architecture specifies the guarantees (e.g.
                  execution speed, failure rate etc). An
                  implementation, a mapping of the requirement on
                  the architecture, is then analyzed for
                  correctness. The orthogonalization of concerns
                  makes the specification and analyses simpler. An
                  effective use of such design methodology has been
                  proposed in Logical Execution Time (LET) model of
                  real-time tasks. The model separates the timing
                  requirements (specified by release and termination
                  instances of a task) from the architecture
                  guarantees (specified by worst-case-execution time
                  of the task). This dissertation proposes a
                  coordination language, Hierarchical Timing
                  Language (HTL), that captures the timing and
                  reliability requirements of real-time
                  applications. An implementation of the program on
                  an architecture is then analyzed to check whether
                  desired timing and reliability requirements are
                  met or not. The core framework extends the LET
                  model by accounting for reliability and
                  refinement. The reliability model separates the
                  reliability requirements of tasks from the
                  reliability guarantees of the architecture. The
                  requirement expresses the desired long-term
                  reliability while the architecture provides a
                  short-term reliability guarantee (e.g.~failure
                  rate for each iteration). The analysis checks if
                  the short-term guarantee ensures the desired
                  long-term reliability. The refinement model allows
                  replacing a task by another task during program
                  execution. Refinement preserves schedulability and
                  reliability, i.e., if a refined task is
                  schedulable and reliable for an implementation,
                  then the refining task is also schedulable and
                  reliable for the implementation. Refinement helps
                  in concise specification without overloading
                  analysis. Along with the formal HTL model and
                  subsequent analyses (both with and without
                  refinement), the work presents a compiler that
                  accepts an HTL program. The compiler checks
                  composition and refinement constraints, performs
                  schedulability and reliability analyses, and
                  generates code for replicated, distributed
                  implementation of the HTL program on a virtual
                  machine. Three real-time controllers, one each
                  from automatic control, automotive control and
                  avionic control, are used to illustrate the steps
                  in modeling and analyzing HTL programs.},
        URL = {http://chess.eecs.berkeley.edu/pubs/400.html}
    }
    

Posted by Arkadeb Ghosal, Ph.D. on 2 Mar 2008.
Groups: chess
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