  This volume contains the proceedings of the Twelfth Workshop on Quantitative
Aspects of Programming Languages and Systems (QAPL 2014), held in Grenoble,
France, on 12 and 13 April, 2014. QAPL 2014 was a satellite event of the
European Joint Conferences on Theory and Practice of Software (ETAPS). The
central theme of the workshop is that of quantitative aspects of computation.
These aspects are related to the use of physical quantities (storage space,
time, bandwidth, etc.) as well as mathematical quantities (e.g. probability and
measures for reliability, security and trust), and play an important (sometimes
essential) role in characterising the behaviour and determining the properties
of systems. Such quantities are central to the definition of both the model of
systems (architecture, language design, semantics) and the methodologies and
tools for the analysis and verification of the systems properties. The aim of
this workshop is to discuss the explicit use of quantitative information such
as time and probabilities either directly in the model or as a tool for the
analysis of systems.
