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Universal Systems Language

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Universal Systems Language (USL) is a modeling language and formal method for the specification and design of software and other complex systems. It was designed by Margaret Hamilton based on her experiences writing flight software for the Apollo program.[1] The language is implemented through the 001 Tool Suite software by Hamilton Technologies, Inc.[2] USL evolved from 001AXES which in turn evolved from AXES all of which are based on Hamilton's axioms of control. The 001 Tool Suite uses the preventive concept of Development Before the Fact (DBTF) for its life-cycle development process. DBTF eliminates errors as early as possible during the development process removing the need to look for errors after-the-fact.

←==Philosophy==→ USL was inspired by Hamilton's recognition of patterns or categories of errors occurring during Apollo software development. Errors at the interfaces between subsystem boundaries accounted for the majority of errors and were often the most subtle and most difficult to find. Each interface error was placed into a category identifying the means to prevent it by way of system definition. This process led to a set of six axioms, forming the basis for a mathematical constructive logical theory of control for designing systems that would eliminate entire classes of errors just by the way a system is defined.[3]

Certain correctness guarantees are embedded in the USL grammar. In contrast to reactive approaches to program verification, testing for errors late into the life cycle, USL's development-before-the-fact philosophy is preventive, not allowing errors in the first place. A USL definition models both its application (for example, an avionics or banking system) and properties of control into its own life cycle.[4] Providing a mathematical framework within which objects, their interactions, and their relationships can be captured, USL – a metalanguage – has "metamechanisms" for defining systems. USL's philosophy is that all objects are recursively reusable and reliable; reliable systems are defined in terms of reliable systems; only reliable systems are used as building blocks; and only reliable systems are used as mechanisms to integrate these building blocks to form a new system. Designers can then use the new system, along with more primitive ones, to define (and build) more comprehensive reliable systems. If a system is reliable, all the objects in all its levels and layers are reliable.

USL is regarded by some users as more user-friendly than other formal systems.[5] It is not only a formalism for software, but also defines ontologies for common elements of problem domains, such as physical space and event timing.

Philosophy

USL was inspired by Hamilton's recognition of patterns or categories of errors occurring during Apollo software development. Errors at the interfaces between subsystem boundaries accounted for the majority of errors and were often the most subtle and most difficult to find. Each interface error was placed into a category identifying the means to prevent it by way of system definition. This process led to a set of six axioms, forming the basis for a mathematical constructive logical theory of control for designing systems that would eliminate entire classes of errors just by the way a system is defined.[6]

Certain correctness guarantees are embedded in the USL grammar. In contrast to reactive approaches to program verification, testing for errors late into the life cycle, USL's development-before-the-fact philosophy is preventive, not allowing errors in the first place. A USL definition models both its application (for example, an avionics or banking system) and properties of control into its own life cycle.[7] Providing a mathematical framework within which objects, their interactions, and their relationships can be captured, USL – a metalanguage – has "metamechanisms" for defining systems. USL's philosophy is that all objects are recursively reusable and reliable; reliable systems are defined in terms of reliable systems; only reliable systems are used as building blocks; and only reliable systems are used as mechanisms to integrate these building blocks to form a new system. Designers can then use the new system, along with more primitive ones, to define (and build) more comprehensive reliable systems. If a system is reliable, all the objects in all its levels and layers are reliable.

USL is regarded by some users as more user-friendly than other formal systems.[8] It is not only a formalism for software, but also defines ontologies for common elements of problem domains, such as physical space and event timing.

Implementation

The process of developing a software system with USL together with its automation, the 001 Tool Suite (001), is as follows: define the system with USL, automatically analyze the definition with 001's analyzer to ensure that USL was used correctly, automatically generate much of the design and all of the implementation code with 001's generator.[9][10][11][12] USL can be used to lend its formal support to other languages.[13]

See also

References

  1. ^ M. Hamilton and W. R. Hackler, "Universal Systems Language: Lessons Learned from Apollo", IEEE Computer, Dec. 2008.
  2. ^ 001 Tool Suite (1986-2016)
  3. ^ Margaret H. Hamilton, Hamilton Technologies (September 27, 2012). ""Universal Systems Language and its Automation, the 001 Tool Suite, for Designing and Building Systems and Software" Lockheed Martin/IEEE Computer Society Webinar Series".
  4. ^ Dolha, Steve, Chiste, Dave, "A Remote Query System for the Web: Managing the Development of Distributed Systems.", Chapter 32, Internet Management, Editor Jessica Keyes, Auerbach, 2000.
  5. ^ Krut, Jr., B., "Integrating 001 Tool Support in the Feature-Oriented Domain Analysis Methodology" (CMU/SEI-93-TR-11, ESC-TR-93-188), Pittsburgh, SEI, Carnegie Mellon University, 1993.
  6. ^ Margaret H. Hamilton, Hamilton Technologies (September 27, 2012). ""Universal Systems Language and its Automation, the 001 Tool Suite, for Designing and Building Systems and Software" Lockheed Martin/IEEE Computer Society Webinar Series".
  7. ^ Dolha, Steve, Chiste, Dave, "A Remote Query System for the Web: Managing the Development of Distributed Systems.", Chapter 32, Internet Management, Editor Jessica Keyes, Auerbach, 2000.
  8. ^ Krut, Jr., B., "Integrating 001 Tool Support in the Feature-Oriented Domain Analysis Methodology" (CMU/SEI-93-TR-11, ESC-TR-93-188), Pittsburgh, SEI, Carnegie Mellon University, 1993.
  9. ^ Ouyang, M., Golay, M.W. 1995, An Integrated Formal Approach for Developing High Quality Software of Safety-Critical Systems, Massachusetts Institute of Technology, Cambridge, Massachusetts, Report No. MIT-ANP-TR-035.
  10. ^ Software Productivity Consortium, (SPC) (1998), Object-Oriented Methods and Tools Survey, Herndon, VA.SPC-98022-MC, Version 02.00.02, December 1998.
  11. ^ Max Schindler (1990) Computer Aided Software Design, John Wiley & Sons, 1990.
  12. ^ * Department of Defense (1992). Software engineering tools experiment-Final report, Vol. 1, Experiment Summary, Table 1, p. 9. Strategic Defense Initiative, Washington, D.C.
  13. ^ Hamilton, M. Hackler, W.R., "A Formal Universal Systems Semantics for SysML, 17th Annual International Symposium, INCOSE 2007, San Diego, CA, June 2007.

Further reading

  • Hamilton, M., Zeldin, S. (1976), "Higher Order Software — A Methodology for Defining Software," IEEE Transactions on Software Engineering, vol. SE-2, no. 1, Mar. 1976.
  • Hamilton, M., Hackler, W.R.. (2004), Deeply Integrated Guidance Navigation Unit (DI-GNU) Common Software Architecture Principles (revised dec-29-04), DAAAE30-02-D-1020 and DAAB07-98-D-H502/0180, Picatinny Arsenal, NJ, 2003–2004.
  • Hamilton, M. and Hackler, W.R. (2007), "Universal Systems Language for Preventative Systems Engineering," Proc. 5th Ann. Conf. Systems Eng. Res. (CSER), Stevens Institute of Technology, Mar. 2007, paper #36.
 
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