K. Jay, L. Kevin, and B. Kenny. Building flexible real-time system using the flex language. IEEE Computer, 1991.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....and real time. In the following subsections several different approaches to real time objects will be reviewed. 1.3. 1 Object Oriented Languages for Real Time The first attempts to enhance an object oriented language, namely C , to become real time capable were the presentations of FLEX [Lin88, Ken94] and RTC [Ish90] These languages contain special constructs for defining deadlines, periods, and synchronization conditions. Some of these constructs can be mapped to scheduler level abstractions, like task deadlines and priorities. The expressiveness of these language add ons is limited (e.g. ....

Kenny, K. B. and K.-J. Lin, Building Flexible Real-Time Systems Using the Flex Language, Computer 24:5, May 1991.

....constraints. Work on run time detection of timing constraint violation has been relatively scarce. In [7] an annotation method was introduced which marks the events of interests in Ada programs and uses Real Time Logic (RTL) formulas to specify the timing constraints to be enforced. In FLEX [4], certain predefined timing constraints can be monitored for violation. The work closest to our research is [1] which presents an event based model for specifying timing constraints to be monitored and proposes two methods for synchronous or asynchronous monitoring of real time constraints. A ....

K.B. Kenny and K.-J. Lin, "Building Flexible RealTime Systems using the FLEX Language", Computer, Vol.24, No.5, May 1991, pp.70-78.

....S2) and let S2.finish correspond to the time that the section ends. Similarly, let S4.start and S4.finish represent the start and finish times of section S4. Using these variables we can represent the section decomposition of a TCEL construct in a manner similar to that found in the Flex language [15]. Recall the flight controller program from Figure 3. Figure 5 illustrates its constituent sections. The constraint expression for S6 corresponds to the program s outer, periodic loop. As the program is in SSA form, O functions appear at confluence points where different values of the same ....

K. B. Kenny and K.-J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer', pages 70 78, May 1991.

....environments, it is useful if the language includes features that can be related to dynamic mechanisms (such as those described in [FJR94] HSNL97] RSYJ97] SH94] for monitoring, diagnosis and recovery. Language support for run time monitoring of real time programs has been addressed in [GKS95] [KL91], Real Time Euclid [KS86] and Ada95 [ANS95] However, this prior work provides limited support for diagnosis and recovery actions. We extend the language features pertaining to diagnosis of timing problems, and to the 41 migration or replication of application program components to handle higher ....

K. B. Kenny and K. J. Lin, "Building Flexible Real-Time Systems Using the Flex Language," IEEE Computer, pages 70--78, May 1991.

.... handlers] These primitives encompass conventional real time constructs such as those found in [GL91] An alternative form under consideration is that of the Flex language, in which conditions specifying inequalities on start, finish, interval and duration times can be attached to timing blocks [KL91] Our measurement of time relies fundamentally on viewing clocks as modules. Time parameters represent ticks on some named virtual clock, which is updated according to an underlying model of time and computation related to that found in [LVB 91] A clock is just a module with an active process ....

K. Kenny and K. Lin, "Building Flexible RealTime Systems Using the Flex Language," IEEE Computer, vol. 24, pp. 70--78, May. 1991.

....delay, wait ff if executed defines an event of duration ff which updates the clock for that process. The duration construct is similar in form to that of the Flex language, in which conditions specifying inequalities on start, finish, interval and duration times can be attached to timing blocks [KL91] The rate construct can now be defined, more precisely, as specifying a constraint on the relative rates of progress of tasks executing in parallel, where progress is the amount of computational work as measured by elapsed ticks on logical clocks local to each process, updated in ....

K. Kenny and K. Lin, "Building flexible realtime systems using the Flex language," IEEE Computer, vol. 24, pp. 70--78, May 1991.

....mechanism allows a high priority task to wait for a low priority task for an unpredictable duration, and consequently processes programmed as Ada tasks would an unpredictable timing behaviour which is an unacceptable for hard real time systems. More specialised programming languages such as Flex [Kenny,91] provide a better handle on achieving the real time constraints by providing timing primitives as part of the language. However, Flex needs a dedicated environment to achieve these results. A different path is advocated by Luqi et al. Luqi,88] where a prototyping language is used. Research into ....

Kenny, K. B. and Lin, K.-J., "Building Flexible Real-Time Systems Using the Flex Language," IEEE Computer, 24(5), pp. 70-78, (May 1991).

....block statements which are inserted in C code. Real Time Concurrent C [18] and RTC [19] are similar systems. The latter supports fine grained constraints by allowing them on individual statements, but they are enforced only at run time, and failure is handled by an exception mechanism. In FLEX [20] timing constraints are specified by constraint blocks which identify constraints to apply during the execution of a block of code. Failure to meet an earliest constraint will produce a delay, while failure to meet a latest constraint (i.e. a deadline) will raise an exception. 7 Future work The ....

K. B. Kenny and K.-J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, 24(5):70--78, May 1991.

....by allowing trace values to be constrained only at times between 0 and . Ideally we want a target programming language which allows timing constraints on code fragments to be expressed directly. Although a handful of programming languages with first class timing constructs have been proposed [25, 11, 10, 5], none has become widely established. Therefore, for the purposes of this paper, we target Dijkstra s guarded command language augmented with timing annotations. The definition of each executable code construct is given in Figure 1 and discussed further in this section. Note that x 2 v is a ....

K.B. Kenny and K-J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, 24(5):70--78, May 1991.

....statement for expressing lower absolute timing bounds, the before coercion gives us a programming language in which blocks of code can be bracketed by precise timing constraints. Although numerous experimental programming languages with first class timing annotations have been proposed previously [32, 6, 17, 18, 31, 7, 5] none has become widely accepted. The simple addition of the before directive to an existing language has a greater chance of industrial uptake than an entirely new language. More importantly, the before directive can be generated as a product of stepwise program refinement [10] thus supporting ....

K. B. Kenny and K.-J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, 24(5):70--78, May 1991.

....refinement algorithm that improves the quality of the result generated by the mandatory part. There is a very large body of work related to scheduling algorithms within this model with various assumptions about characteristics of the tasks to be scheduled [Chung et al. 1990, Marlin et al. 1990, Kenny and Lin, 1991, Shih et al. 1991, Liu et al. 1991b, Liu et al. 1991a, Leung et al. 1992, Ho et al. 1992, Dey et al. 1993] The emphasis in most of this work has been on finding optimal polynomial time scheduling algorithms for strongly circumscribed problems within this area. Examples of problems for ....

Kevin B. Kenny and Kwei-Jay Lin. Building flexible real-time systems using the Flex language. IEEE Computer, 24(5):70--78, May 1991.

....useful if the language includes features that can be related to dynamic mechanisms (such as those described in [FJR94] HSNL97] RLLS97] RSYJ97] SH94] for monitoring, diagnosis and recovery. Language support for run time monitoring of real time programs has been addressed in [JRR94] GKS95] [KL91], Real Time Euclid [KS86] and Ada95 [ANS95] However, limited support was provided for diagnosis and recovery actions. Our work extends the language features pertaining to diagnosis of timing problems, and the migration or replication of software components to handle higher data stream or event ....

K. B. Kenny and K. J. Lin, Building flexible real-time systems using the flex language, IEEE Computer, pages 70--78, May 1991.

....embedding the timing information inside the computational code. In general, as a real time programming language, Ada lacks adequate capabilities for expressing and enforcing temporal relations between and within different execution units in distributed systems. FLEX The programming language Flex [54, 47] is a derivative of C . It provides a new language construct, constraint block , to describe constraints on time as well as other resources. A constraint block identifies restrictions that must apply while a section of code is in execution. It takes the form: label: constraint; constraint; ....

Kevin B. Kenny and Kwei-Jay Lin. Building Flexible Real-Time Systems Using the Flex Language. IEEE Computer, 24(5):70 --- 78, 1991.

....S2) and let S2.finish correspond to the time that the section ends. Similarly, let S4.start and S4.finish represent the start and finish times of section S4. Using these variables we can represent the section decomposition of a TCEL construct in a manner similar to that found in the Flex language [15]. Recall the flight controller program from Figure 3. Figure 5 illustrates its constituent sections. The constraint expression for S6 corresponds to the program s outer, periodic loop. As the program is in SSA form, OE functions appear at confluence points where different values of the same ....

K. B. Kenny and K.-J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, pages 70--78, May 1991.

....theoretical foundation, but it appears to be a desirable model for the distributed artificial intelligence applications likely to make up the NPS AUV. In this regard the FLEX programming language is worth consideration since it implements dynamic scheduling theory and generates C code as output [KL91]. Additionally, there exists a hybrid approach known as a mixed priority system that combines the best features of rate monotonic scheduling and dynamic scheduling [Lea91] Formal evaluation of the mixed priority approach also appears worthwhile. Given that AUV related research is likely to ....

K.B. Kenny and K-J. Lin. "Building Flexible Real-Time Systems using the Flex Language," Computer, Vol 24, No 5, May 1991, pp 70-78.

....S2) and let S2.finish correspond to the time that the section ends. Similarly, let S4.start and S4.finish represent the start and finish times of section S4. Using these variables we can represent the section decomposition of a TCEL construct in a manner similar to that found in the Flex language [15]. Recall the robot controller program from Figure 3. Figure 5 illustrates its constituent sections, where the bracketed numbers are the maximum execution times for each instruction on the given CPU. These times are generated by a timing analysis tool, such as those found in [10, 5, 25, 27, 32] ....

K. Kenny and K. J. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, pages 70--78, May 1991.

....in active real time databases which (1) solves the ambiguity problems mentioned in the previous section and (2) permits the efficient detection algorithms in [18, 19] to be applied to active, real time databases. 1. 1 Related Work Runtime monitoring of timing constraints have been investigated in [4, 13, 17, 20, 18, 19]. In [17] an annotation method was introduced which marks the events of interests in Ada programs and uses RTL (Real Time Logic) formulas to specify the timing constraints to be enforced. In FLEX [13] certain predefined timing constraints can be monitored for violation. 4] presents an ....

....Work Runtime monitoring of timing constraints have been investigated in [4, 13, 17, 20, 18, 19] In [17] an annotation method was introduced which marks the events of interests in Ada programs and uses RTL (Real Time Logic) formulas to specify the timing constraints to be enforced. In FLEX [13], certain predefined timing constraints can be monitored for violation. 4] presents an event based model for specifying timing constraints to be monitored and proposes two methods for synchronous or asynchronous monitoring of real time constraints. A timing constraint satisfiability checking ....

K.B. Kenny and K.-J. Lin, "Building Flexible Real-Time Systems using the FLEX Language", Computer, Vol.24, No.5, May 1991, pp.70-78.

....our real time data model design, namely, to provide facilities for simplifying reuse of time constrained modules, and consequently, increasing the productivity of real time application developers and optimizing the utility of resources. None of the existing models used for real time applications [4, 10, 15, 17, 20, 24, 47] is found to provide sufficient support in this regard. Based on this observation, we first extract a simple yet powerful real time object oriented data model 1 called ROMPP, Real time Object Model with Performance Polymorphism [49] ROMPP explicitly captures the important characteristics of ....

....model as the programmingmodel of object oriented paradigm,and the object oriented data model as the extension of the programming model in the realm of database management. We make no such distinction and will use the terms interchangeably. 2 The term performance polymorphism first appeared in [17]. mance polymorphism, they neither explicitly capture these concepts nor provide a mechanism to enforce them. By contrast, ROMPP offers not only explicit constructs for timing specifications but also an automated mechanism to support performance polymorphism. We then develop a framework for ....

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K.B. Kenny, and K.-J. Lin, "Building Flexible Real-Time Systems Using the Flex Language," IEEE Computer, May 1991, pp. 70-78.

.... may be used to implement synchronisation variables from [20] these variables would be constraint internal data) ffl control of the concurrency level within a method or within the object, ffl timing control (e.g. earliest and latest method start time and end time, method duration from [3] and [36]) ffl method pre and post conditions, method and object invariants used for the runtime verification of object consistency and application correctness. In addition to accessing and possibly modifying the instance variables and constraint data, Pre and Post constraints can announce an event, ....

....addition to accessing and possibly modifying the instance variables and constraint data, Pre and Post constraints can announce an event, and Pre constraints can request that the current notification is: discarded, enqueued, or processed. This allows constraints to have wait or failure semantics [36]. In the case of failure semantics a constraint is used only to monitor a certain 4 It is assumed that each object has a unique identifier. 5 source is used in a Notify constraint for the identity of the source object condition (e.g. the values of some instance variables) When a ....

[Article contains additional citation context not shown here]

K.B. Kenny and K. Lin. Building flexible real-time systems using the Flex language. IEEE Computer, 24(5):70--78, May 1991.

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K. Jay, L. Kevin, and B. Kenny. Building flexible real-time system using the flex language. IEEE Computer, 1991.

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Kenny, K., Lin, K.J.: Building flexible real-time systems using the Flex language. IEEE Computer 24 (1991) 70--78

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K. B. Kenny, K. Lin, "Building Flexible Real-Time Systems Using the Flex Language", IEEE Computer, May 1991.

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K. B. Kenny and K. Lin, "Building Flexible Real-Time Systems Using the Flex Language", IEEE Computer, 24(5), pp. 70-78, May 1991.

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KENNY,K.B.AND LIN, K.-J. 1991. Building flexible real-time systems using the Flex language. IEEE Comput. 24, 5, 70--78.

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Ken91. Kenny, K. B. and Lin, K. J., "Building Flexible Real-Time Systems Using the Flex Language", Computer 24(5), pp. 70-78 (May 1991).

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