Real-Time for the Real World ™
Work-in-progress preview of a work-in-progress book:
Introduction to Fundamentals of Timeliness
in Dynamically Real-Time Systems [Jensen 201x]
Informally, a system is a “real-time” one if its core properties of timeliness and predictability of timeliness are integral to its logic, not just performance measures. In general, those properties are dynamic due primarily to intrinsic epistemic uncertainties—notably, ignorance—about properties of the system and its application environment. Despite such uncertainties, dynamically real-time systems have multiple application-specific kinds and degrees of criticality—including even the most extreme safety-critical systems (e.g., for warfare). Traditional real-time computing systems are a special case whose core properties are predominately static and presumed to be known á priori, thus greatly limiting those systems’ applicability. Many dynamically real-time systems exist, built by application domain experts outside the real-time field, but without the benefits of a coherent foundation for real-time per se. The design, implementation, and application of real-time systems (both static and dynamic) can be extended and strengthened by creating such a foundation based on first principles for those core properties. This book introduces one approach to that. Timeliness is dynamically expressive using time/utility functions. Uncertainty of timeliness predictability can be reasoned about using various mathematical theories of evidence (belief functions) such as Dempster-Shafer theory. This foundation has been successfully employed in different real-time contexts having wickedly dynamic core properties, where traditional static real-time perspectives and traditions were inappropriate.
N.B. There still are pages from the previous (c. 2008-2012) version of this site which I have not yet updated and integrated (or removed).