Extended portal: violating the assignment rule and enforcing the single parent rule

ABSTRACT

One of the main drawbacks of programming with the RTSJ (The Real-time Specification for Java) is probably its special model of references. The restrictions imposed by the assignment and single parent rules constrains the programming model in such a way that it is sometimes more difficult to use than the Java one. The community has faced this problem producing a special and new set of programming paradigms and patterns, designed to be used in collaboration with the region-based model; this enhances the range of application that may be constructed with it. However, the current version of RTSJ does not have general mechanisms that enable to perform safe violations of the assignment rule in an easy way.In this paper, we address this issue by introducing a new extension named extended portal. This extension (that has an interface that is very close to the current RTSJ portals) introduces mechanisms that allow a safe violation of the assignment rules, providing also an easy navigation mechanism for accessing the creation context of an object. Using this extension, the programmer can have access to a forbidden reference in two steps, reducing the complexity from Θ (n) of the current portals to Θ (1) of the extended ones. The work is mainly concentrated on the justification of the utility and feasibility of the extension. To clarify this idea, an example that illustrates the drawbacks of the current portals and the benefits of the extended ones is described. Also, a Java interface and a set of low level changes required at the implementation level are explained.

REFERENCES

• 1: Pablo Basanta-Val , Marisol García-Valls , Iria Estévez-Ayres, AGCMemory: a new real-time Java region type for automatic floating garbage recycling, ACM SIGBED Review, v.2 n.3, p.7-12, July 2005 [doi>10.1145/1121802.1121805]
• 2: Pablo Basanta-Val , Marisol Garcia-Valls , Iria Estevez-Ayres, Towards the Integration of Scoped Memory in Distributed Real-Time Java, Proceedings of the Eighth IEEE International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC'05), p.382-389, May 18-20, 2005 [doi>10.1109/ISORC.2005.61]
• 3: Pablo Basanta-Val, Marisol García-Valls, Iria Estévez-Ayres. "No Heap Remote Objects: Leaving Out Garbage Collection at the Server Side". OTM Workshops 2004: Workshop on Java Technologies for Real-Time and Embedded Systems. OTM Workshops 2004: Workshop on Java Technologies for Real-Time and Embedded Systems. pp. 359--370
• 4: Edward G. Benowitz, Albert F. Niessner. "A Patterns Catalog for RTSJ Software Designs". OTM Workshops 2003: Workshop on Java Technologies for Real-Time and Embedded Systems. 497--507
• 5: Greg Bollella , Tim Canham , Vanessa Carson , Virgil Champlin , Daniel Dvorak , Brian Giovannoni , Mark Indictor , Kenny Meyer , Alex Murray , Kirk Reinholtz, Programming with non-heap memory in the real time specification for Java, Companion of the 18th annual ACM SIGPLAN conference on Object-oriented programming, systems, languages, and applications, October 26-30, 2003, Anaheim, CA, USA [doi>10.1145/949344.949443]
• 6: Andrew Borg, Andy J. Wellings. "A Real-Time RMI Framework for the RTSJ". ECRTS 2003: 15th Euromicro Conference on Real-Time Systems, 2-4 July 2003, Porto, Portugal. pp. 238--248
• 7: Andrew Borg, Andy J. Wellings. "Reference Objects for RTSJ Memory Areas". OTM Workshops 2003: Workshop on Java Technologies for Real-Time and Embedded Systems. pp. 397--410
• 8: Angelo Corsaro, Corrado Santoro. "Design Patterns for RTSJ Application Development". OTM Workshops 2004: Workshop on Java Technologies for Real-Time and Embedded Systems. pp.394--405
• 9: Angelo Corsaro , Ron K. Cytron, Efficient memory-reference checks for real-time java, Proceedings of the 2003 ACM SIGPLAN conference on Language, compiler, and tool for embedded systems, June 11-13, 2003, San Diego, California, USA
• 10: Peter C. Dibble. "Real-time Java Platform Programming". Prentice Hall PTR; 1st edition (March 11, 2002). ISBN: 0130282618
• 11: M. T. Higuera-Toledano, Analyzing the Memory Management Semantic and Requirements of the Real-time Specification of Java JSR-0000001, Proceedings of the Ninth IEEE International Symposium on Object and Component-Oriented Real-Time Distributed Computing (ISORC'06), p.419-423, April 24-26, 2006 [doi>10.1109/ISORC.2006.17]
• 12: JSR-282. "RTSJ version 1.1". Available on-line at http://www.jcp.org/en/jsr/detail?id=282
• 13: Sheng Liang, Java Native Interface: Programmer's Guide and Reference, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1999
• 14: F. Pizlo, J. M. Fox, David Holmes, Jan Vitek. "Real-Time Java Scoped Memory: Design Patterns and Semantics". ISORC 2004: 7th IEEE International Symposium on Object-Oriented Real-Time Distributed Computing, 12-14 May 2004, Vienna pp. 101--110
• 15: Krishna Raman, Yue Zhang, Mark Panahi, Juan A. Colmenares, Raymond Klefstad, Trevor Harmon. "RTZen: Highly Predictable, Real-Time Java Middleware for Distributed and Embedded Systems". Middleware 2005: ACM/IFIP/USENIX, 6th International Middleware Conference, Grenoble, France, November 28 - December 2, 2005. pp. 225--248
• 16: Krishna Raman , Yue Zhang , Mark Panahi , Juan A. Colmenares , Raymond Klefstad, Patterns and Tools for Achieving Predictability and Performance with Real-Time Java, Proceedings of the 11th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA'05), p.247-253, August 17-19, 2005 [doi>10.1109/RTCSA.2005.68]
• 17: RTJEG. "The Real-time Java Specification". Version 1.0.1(b). Available on-line at http://www.rtj.org
• 18: Timesys. "JTIME RTSJ 1.0 Extensions User Guide". Available on-line at http://www.timesys.com

INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features

General Terms:
Algorithms, Design

Keywords:
assignment rule violation, real-time java, scoped memory