1,295 research outputs found
Overcoming observability problems in distributed test architectures
This paper investigates conditions that must be satisfied by an FSM for the existence
of input sequences that can be applied in a distributed test architecture
without encountering controllability and observability problems and without
using external coordination messages. Such conditions have two potential values.
First, they can be used to determine whether we require coordination
messages and thus a network that connects the testers. Second, if we wish to
avoid the use of coordination messages in testing then these conditions can be
seen as testability conditions that can inform the design process. Results given
in this paper differ from those in the following ways. First, the conditions
are strictly weaker than those in since we are less restrictive in the
ways we achieve our goals. Second, only considered observability problems;
we consider both controllability and observability problems. In addition,
only considered a particular type of observability problem and we generalize
this. Finally, we investigate the situation in which we need only add input
sequences to complement a given test/checking sequence Ļ and prove that the
conditions for this problem are equivalent to those for the original problem
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Checking sequences for distributed test architectures
Controllability and observability problems may manifest themselves during the application of a checking sequence in a test architecture where there are multiple remote testers. These problems often require the use of external coordination message exchanges among testers during testing. However, the use of coordination messages requires the existence of an external network that can increase the cost of testing and can be difficult
to implement. In addition, the use of coordination messages introduces delays and this can cause problems where there are timing constraints. Thus, sometimes it is desired to construct a checking sequence from the specification of the system under test that will be free from controllability and observability problems without requiring the use of external coordination message exchanges. This paper gives conditions under which it is possible to produce such a checking sequence, using multiple distinguishing sequences, and an algorithm that achieves this
Using status messages in the distributed test architecture
If the system under test has multiple interfaces/ports and these
are physically distributed then in testing we place a tester at
each port. If these testers cannot directly communicate with one
another and there is no global clock then we are testing in the
distributed test architecture. If the distributed test
architecture is used then there may be input sequences that cannot
be applied in testing without introducing controllability
problems. Additionally, observability problems can allow fault
masking. In this paper we consider the situation in which the
testers can apply a status message: an input that causes the
system under test to identify its current state. We show how such
a status message can be used in order to overcome controllability
and observability problems
Overcoming controllability problems in distributed testing from an input output transition system
This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 Springer VerlagThis paper concerns the testing of a system with physically distributed interfaces, called ports, at which it interacts with its environment. We place a tester at each port and the tester at port p observes events at p only. This can lead to controllability problems, where the observations made by the tester at a port p are not sufficient for it to be able to know when to send an input. It is known that there are test objectives, such as executing a particular transition, that cannot be achieved if we restrict attention to test cases that have no controllability problems. This has led to interest in schemes where the testers at the individual ports send coordination messages to one another through an external communications network in order to overcome controllability problems. However, such approaches have largely been studied in the context of testing from a deterministic finite state machine. This paper investigates the use of coordination messages to overcome controllability problems when testing from an input output transition system and gives an algorithm for introducing sufficient messages. It also proves that the problem of minimising the number of coordination messages used is NP-hard
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Overcoming controllability problems with fewest channels between testers
When testing a system that has multiple physically distributed
ports/interfaces it is normal to place a tester at each port. Each
tester observes only the events at its port and it is known that
this can lead to additional controllability problems. While such
controllability problems can be overcome by the exchange of
external coordination messages between the testers, this requires
the deployment of an external network and may thus increase the
costs of testing. The problem studied in this paper is finding a
minimum number of coordination channels to overcome
controllability problems in distributed testing. Three instances
of this problem are considered. The first problem is to find a
minimum number of channels between testers in order to overcome
the controllability problems in a given test sequence to be
applied in testing. The second problem is finding a minimal set of
channels that allow us to overcome controllability problems in any
test sequence that may be selected from the specification of the
system under test. The last problem is to find a test sequence
that achieves a particular test objective and in doing so allows
fewest channels to be used
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Controllable testing from nondeterministic finite state machines with multiple ports
Copyright @ 2011 IEEESome systems have physically distributed interfaces, called ports, at which they interact with their environment. We place a tester at each port and if the testers cannot directly communicate and there is no global clock then we are using the distributed test architecture. It is known that this test architecture introduces controllability problems when testing from a deterministic finite state machine. This paper investigates the problem of testing from a nondeterministic finite state machine in the distributed test architecture and explores controllability. It shows how we can decide in polynomial time whether an input sequence is controllable. It also gives an algorithm for generating such an input sequence bar{x} and shows how we can produce testers that implement bar{x}
Model-Based Testing for the Cloud
Software in the cloud is characterised by the need to be highly adaptive and continuously available. Incremental changes are applied to the deployed system and need to be tested in the field. Different configurations need to be tested. Higher quality standards regarding both functional and non-functional properties are put on those systems, as they often face large and diverse customer bases and/or are used as services from different peer service implementations. The properties of interest include interoperability, privacy, security, reliability, performance, resource use, timing constraints, service dependencies, availability, and so on. This paper discusses the state of the art in model-based testing of cloud systems. It focuses on two central aspects of the problem domain: (a) dealing with the adaptive and dynamic character of cloud software when tested with model-based testing, by developing new online and offline test strategies, and (b) dealing with the variety of modeling concerns for functional and non-functional properties, by devising a unified framework for them where this is possible. Having discussed the state of the art we identify challenges and future directions
Microservices Security Challenges and Approaches
The fast-paced development cycles of microservices applications increase the probability of insufficient security tests in the development pipelines and consequent deployment of vulnerable microservices. The distribution and ephemeral of microservices create a discoverability challenge for traditional security assessment techniques, especially for microservices being dynamically launched and de-registered. To address this in applications and networks, continuous security assessments are used for vulnerability detection. Detected vulnerabilities are thereafter patched, essentially reducing the chances for security attacks. This paper illustrates the microservices architecture and its components from the security perspective. It investigates, summarizes, and highlights the microservices security-related challenges and the suggested approaches and proposals for facing them. It addresses the security impact on the different microservice architectural perspectives
Deep Variational Reinforcement Learning for POMDPs
Many real-world sequential decision making problems are partially observable
by nature, and the environment model is typically unknown. Consequently, there
is great need for reinforcement learning methods that can tackle such problems
given only a stream of incomplete and noisy observations. In this paper, we
propose deep variational reinforcement learning (DVRL), which introduces an
inductive bias that allows an agent to learn a generative model of the
environment and perform inference in that model to effectively aggregate the
available information. We develop an n-step approximation to the evidence lower
bound (ELBO), allowing the model to be trained jointly with the policy. This
ensures that the latent state representation is suitable for the control task.
In experiments on Mountain Hike and flickering Atari we show that our method
outperforms previous approaches relying on recurrent neural networks to encode
the past
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