  The lack of ultimate scaling relations for previtreous changes of the primary
relaxation time or viscosity in glass-forming systems constitutes the grand
fundamental challenge, also hindering the development of relevant material
engineering applications. The report links the problem to the location of the
previtreous domain remote from a hypothetical singularity. As the solution, the
linearized, distortions-sensitive analysis is proposed. It is developed for
scaling-relations linked to basic glass transition models: free volume,
entropic, critical-like, avoided criticality, and kinetically constrained
approaches. For all model scaling relations their alternative formulations
based on fragility, the semi-universal metric of dynamics, are presented. The
distortions-sensitive analysis is supplemented by the alternative approach
based on the activation energy index showing its relative changes on cooling in
the previtreous region. The search for the coherent description of the
previtreous dynamics in the homologous series of polyols, from glycerol to
sorbitol, is used to present in practice and validate the application of the
distortions sensitive analysis. Only two scaling equation, MYEGA and the recent
'activation and critical' (AC), passed such exam. They also revealed a limited
reliability of the Stickel operator' analysis for detecting the dynamic
crossover. The report constitutes the unique tool-guide for applications, and a
checkpoint analysis of the glass transition models. The discussion focuses on
the temperature path on cooling but the extension for the still hardly
discussed pressure path is also discussed.
