Extensions
With the addition of certain features to the existing petrinet, several extentions can be formulated, that peform extended functions. There are two major types of extensions of petri nets.
Types of Extensions
1) completely backwards-compatible
Backward compatibility of a petrinet is decided based on whether it can be reverted to the original petri net after the extension or not. These petrinets are usually extended via a mathematical formula, and hence they can be reversed. Coloured Petrinets are examples for backward compatible petrinets. If the properties can be modelled in the original petrinet, they are not real extensions.
2) Non backwards compatible
These are the petrinets whose extensions cannot be reverted to get back the original petriet. For example, timed petrinets cannot be reversed from theoir extended versions since it is a function of time. Non backward compatible Extensions are sometimes very powerful, but they do not possess the full range of mathematical tools that are available for the analysis of normal Petri nets.
Types of important extended petrinets
1) Additional types of arcs
a) Reset arc
This type of arc never imposes any precondition on firing. It also empties the place upon firing of the transition, thus making it difficult of impossible to decide the reachability. However, in the reset arc, properties like termination are decidable.
b) Inhibitor Arc
This type of arc imposes precondition which allows firing of the transition only when the place is empty. Furthermore, it allows arbitrary computations on the number of tokens.
2) Colored Petrinets
Unlike the indistinguishable feature of tokens in standard petrinets, every token carries a value in a Colored Petri net. CPN tools ar...
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...ollows
Fig. Example of a Marked Graph
3) Free Choice
Here, an arc from a place to a transition can either be the only arc from that place or the only arc to that transition. Concurrency and conflict can exist, but not at the same time.
4) Extended Free Choice
These petri nets are a super set of free choice that can be transformed into a free choice.
5) Asymmetric Choice Net
Incase of Asymmmetric Choice Net, 'confusion', or concurrency and conflict may occur, but they will not occur symmetrically. Mathematically, it can be represented as follows
extensions, restrictions are also possible and done on petri nets. We obtain restricted petrinet by suppressing certain features of the ordinary petri nets. In ordiary petri nets, all the are weights are one
Works Cited
http://embedded.eecs.berkeley.edu/Respep/Research/hsc/class.F03/ee249/discussionpapers/PetriNets.pdf
4. When a CS is not followed by a UCS, the subsequent fading of a CR is called:
Pet_Net had been off to a great start, but as of late, they have been under some scrutiny. Complications with two of Pet_Net’s dog sitters have placed the company in uncomfortable situations. The first event occurred while a Pet_Net dog sitter was taking a clients dog for a walk in a nearby park. At the moment, with nobody in sight, the sitter let the dog off of the leash. Moments later, a mother and child entered the park. The dog overexcitedly greeted the small child, knocking him over, and breaking his arm. The family is now pressing charges of negligence against Pet_Net and the sitter. The next event occurred while a Pet_Net sitter was looking after a dog at the client’s residence and discovered that the dog looked ill. The sitter took the dog to the vet, but incurred over $2,000 for the emergency service, which the owner is claiming they will not pay. It is
2) Whatever is moved is moved by another [for nothing can be or should be moved itself (pg. 128)]
...e fuse of past and present, something which has developed throughout Maus 1 and Maus 2.
... choose to change a part of that chain. Introducing an indetermined event, by which the determined course will shift, creating another determined course that includes the indetermined act.
Stage 3 involves creating an Architectural Model version of the whole system including sub systems. A Viewpoint Hierarchy shows a skeleton version of the system which can be ins...
...ate shifting situation. This process continuously occurs during the life of the policy do to individuals, organizations, or interest groups who benefit from a particular policy may seek to adjust the increase or maintain the benefits. In the other hand, people who are negatively affected by a policy may seek out to reduce the negative consequences (Longest, 2010).
allow for each subsequent step to take place. And after each step it becomes increasingly
Jackson, F., and Pettit, P., 1990, 'Program Explanation: a general perspective', Analysis, vol. 50, pp. 107-117.
Vassiliadis, P., Simitsis, A., & Skiadopoulos, S. (2002, January). On the logical modeling of ETL processes. In Advanced Information Systems Engineering (pp. 782-786). Springer Berlin Heidelberg.
The OSI model provided for a solution to this problem. The model organized those tasks that are essential for computer network operation, into seven groups. These groups were called layers. All manufacturers of computing equipment were recommended to make their products compliant with the OSI model. This meant that each computing product was to perform the functions associated with a specific layer within the model; any method of accomplishing these functions was acceptable. In a network composed of equipment that operated according to OSI guidelines, a separate product would be used to perform each layer of OSI functionality. Thus, all elements of the network would be aware of the specific jobs performed by every other network element; this would allow for compatibility between networking products that were created by different vendors. By designing networks according to OSI guidelines, the networker was able to combine any group of products, made by any number of vendors, into a functioning computer network (Stamper 28).
What are the three or four most important drivers of Microsoft’s business model over the past 10 to 15 years that have accounted for the company’s spectacular results?
International Seminar on Model-Based Engineering of Embedded Real-Time Systems, G. (2010). Model-based engineering of embedded real-time systems: International Dagstuhl Workshop, Dagstuhl Castle, Germany, November 4-9, 2007 : revised selected papers. Berlin: Springer.
As software engineering is still a young science the debate around the most optimine practices remains volatile.As process models become better defined, it becomes easier to describe them in a computer readable language. Being able to define a problem in such a way is a key factor in creating automated processes. When an adequate process model has been proposed and defined, process technology tools can be used to evaluate the tasks as characterised by the process model. Functionality of these process technology tools can include designating tasks within stages of the model and monitoring the progress and success of them. (Royce, 2005). As the models become better defined it may even be possible to have software controlling process by utilising optimisation methods. However the difficulty in reaching this level of automation is that clear heuristics are required for what qualifies as a successful model, heuristics that are computable. With clear heuristics for success of a model, such as low time or cost, the typical workflow of a model can be evaluated against alternate workflows to determine the most time or cost effective path (Royce, 2005). Using these tools, computer optimised process models can be used to select the perfect process model for certain projects. There is the potential for process models to be tailor made for each project via
This contention is an advantage in information theory since it fully distinguishes between digital information and ordinary commodities [riis, max Equational logic] which, in follows, can be used for boosting throughput, scalability and efficiency of information networks.[]