9,440 research outputs found
Extending the Real-Time Maude Semantics of Ptolemy to Hierarchical DE Models
This paper extends our Real-Time Maude formalization of the semantics of flat
Ptolemy II discrete-event (DE) models to hierarchical models, including modal
models. This is a challenging task that requires combining synchronous
fixed-point computations with hierarchical structure. The synthesis of a
Real-Time Maude verification model from a Ptolemy II DE model, and the formal
verification of the synthesized model in Real-Time Maude, have been integrated
into Ptolemy II, enabling a model-engineering process that combines the
convenience of Ptolemy II DE modeling and simulation with formal verification
in Real-Time Maude.Comment: In Proceedings RTRTS 2010, arXiv:1009.398
Event-Clock Nested Automata
In this paper we introduce and study Event-Clock Nested Automata (ECNA), a
formalism that combines Event Clock Automata (ECA) and Visibly Pushdown
Automata (VPA). ECNA allow to express real-time properties over non-regular
patterns of recursive programs. We prove that ECNA retain the same closure and
decidability properties of ECA and VPA being closed under Boolean operations
and having a decidable language-inclusion problem. In particular, we prove that
emptiness, universality, and language-inclusion for ECNA are EXPTIME-complete
problems. As for the expressiveness, we have that ECNA properly extend any
previous attempt in the literature of combining ECA and VPA
Indefinite waitings in MIRELA systems
MIRELA is a high-level language and a rapid prototyping framework dedicated
to systems where virtual and digital objects coexist in the same environment
and interact in real time. Its semantics is given in the form of networks of
timed automata, which can be checked using symbolic methods. This paper shows
how to detect various kinds of indefinite waitings in the components of such
systems. The method is experimented using the PRISM model checker.Comment: In Proceedings ESSS 2015, arXiv:1506.0325
Nested Partially-Latent Class Models for Dependent Binary Data; Estimating Disease Etiology
The Pneumonia Etiology Research for Child Health (PERCH) study seeks to use
modern measurement technology to infer the causes of pneumonia for which
gold-standard evidence is unavailable. The paper describes a latent variable
model designed to infer from case-control data the etiology distribution for
the population of cases, and for an individual case given his or her
measurements. We assume each observation is drawn from a mixture model for
which each component represents one cause or disease class. The model addresses
a major limitation of the traditional latent class approach by taking account
of residual dependence among multivariate binary outcome given disease class,
hence reduces estimation bias, retains efficiency and offers more valid
inference. Such "local dependence" on a single subject is induced in the model
by nesting latent subclasses within each disease class. Measurement precision
and covariation can be estimated using the control sample for whom the class is
known. In a Bayesian framework, we use stick-breaking priors on the subclass
indicators for model-averaged inference across different numbers of subclasses.
Assessment of model fit and individual diagnosis are done using posterior
samples drawn by Gibbs sampling. We demonstrate the utility of the method on
simulated and on the motivating PERCH data.Comment: 30 pages with 5 figures and 1 table; 1 appendix with 4 figures and 1
tabl
Steps Towards a Method for the Formal Modeling of Dynamic Objects
Fragments of a method to formally specify object-oriented models of a universe of discourse are presented. The task of finding such models is divided into three subtasks, object classification, event specification, and the specification of the life cycle of an object. Each of these subtasks is further subdivided, and for each of the subtasks heuristics are given that can aid the analyst in deciding how to represent a particular aspect of the real world. The main sources of inspiration are Jackson System Development, algebraic specification of data- and object types, and algebraic specification of processes
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