3,562 research outputs found
Synthesis in Distributed Environments
Most approaches to the synthesis of reactive systems study the problem in terms of a two-player game with complete observation. In many applications, however, the system\u27s environment consists of several distinct entities, and the system must actively communicate with these entities in order to obtain information available in the environment. In this paper, we model such environments as a team of players and keep track of the information known to each individual player. This allows us to synthesize programs that interact with a distributed environment and leverage multiple interacting sources of information.
The synthesis problem in distributed environments corresponds to solving a special class of Petri games, i.e., multi-player games played over Petri nets, where the net has a distinguished token representing the system and an arbitrary number of tokens representing the environment. While, in general, even the decidability of Petri games is an open question, we show that the synthesis problem in distributed environments can be solved in polynomial time for nets with up to two environment tokens. For an arbitrary but fixed number of three or more environment tokens, the problem is NP-complete. If the number of environment tokens grows with the size of the net, the problem is EXPTIME-complete
Performance evaluation using timed coloured Petri nets
Colored Petri nets are Petri nets in which attributes are associated with individual tokens. These attributes are called colors. The set of colors is finite. Colors can be modified during transition firings, and the same transition can perform different transformations for tokens of different colors. Colors can thus distinguish tokens, and this allows one to fold similar subnets of a net into a single subnet, reducing the model complexity. In timed colored nets. the transitions fire in real-time, i.e., there is a firing-time associated with each color and each transition of a net. A state description of timed nets is proposed which represents the behavior of a timed colored net by a probabilistic state graph. Performance analysis of timed colored nets is based on stationary probabilities of state
Abridged Petri Nets
A new graphical framework, Abridged Petri Nets (APNs) is introduced for
bottom-up modeling of complex stochastic systems. APNs are similar to
Stochastic Petri Nets (SPNs) in as much as they both rely on component-based
representation of system state space, in contrast to Markov chains that
explicitly model the states of an entire system. In both frameworks, so-called
tokens (denoted as small circles) represent individual entities comprising the
system; however, SPN graphs contain two distinct types of nodes (called places
and transitions) with transitions serving the purpose of routing tokens among
places. As a result, a pair of place nodes in SPNs can be linked to each other
only via a transient stop, a transition node. In contrast, APN graphs link
place nodes directly by arcs (transitions), similar to state space diagrams for
Markov chains, and separate transition nodes are not needed.
Tokens in APN are distinct and have labels that can assume both discrete
values ("colors") and continuous values ("ages"), both of which can change
during simulation. Component interactions are modeled in APNs using triggers,
which are either inhibitors or enablers (the inhibitors' opposites).
Hierarchical construction of APNs rely on using stacks (layers) of submodels
with automatically matching color policies. As a result, APNs provide at least
the same modeling power as SPNs, but, as demonstrated by means of several
examples, the resulting models are often more compact and transparent,
therefore facilitating more efficient performance evaluation of complex
systems.Comment: 17 figure
Formalization of Petri Nets with Individual Tokens as Basis for DPO Net Transformations
Reconfigurable place/transition systems are Petri nets with initial markings
and a set of rules which allow the modification of the net structure during runtime.
They have been successfully used in different areas like mobile ad-hoc networks.
In most of these applications the modification of net markings during runtime
is an important issue. This requires the analysis of the interaction between firing and
rule-based modification. For place/transition systems this analysis has been started
explicitly without using the general theory of M-adhesive transformation systems,
because firing cannot be expressed by rule-based transformations for P/T systems in
this framework. This problem is solved in this paper using the new approach of P/T
nets with individual tokens. In our main results we show that on one hand this new
approach allows to express firing by transformation via suitable transition rules. On
the other hand transformations of P/T nets with individual tokens can be shown to
be an instance ofM-adhesive transformation systems, such that several well-known
results, like the local Church-Rosser theorem, can be applied. This avoids a separate
conflict analysis of token firing and transformations. Moreover, we compare
the behavior of P/T nets with individual tokens with that of classical P/T nets. Our
new approach is also motivated and demonstrated by a network scenario modeling
a distributed communication system
RONs Revisited: General Approach to Model Reconfigurable Object Nets based on Algebraic High-Level Nets
Reconfigurable Object Nets (RONs) have been implemented in our
group to support the visual specification of controlled rule-based transformations
of marked place/transition (P/T) nets. RONs are high-level nets (system nets) with
two types of tokens: object nets (P/T nets) and net transformation rules. System net
transitions can be of different types to fire object net transitions, move object nets
through the system net, or to apply a net transformation rule to an object net. The
disadvantage of the RON approach and tool is the limitation of object nets to P/T
nets and the limitation of the underlying semantics of RONs due to the fixed types
for system net transitions. Often, a more general approach is preferred where the
type of object nets and the behavior of reconfigurations may be defined in a more
flexible way. In this paper, we propose to use Algebraic High-Level nets with individual
tokens (AHLI nets) as system nets. In this more general approach, tokens
may be any type of Petri nets, defined by the corresponding algebraic signature and
algebra. To support this general approach, a development environment for AHLI
nets is currently implemented which allows the user to edit and simulate AHLI nets.
We present the formalization of RONs as special AHLI nets and describe the current
state of the AHLI net tool environment
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