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Nets Within Nets
Nets within Nets is a modelling method belonging to the family of Petri nets. This method is distinguished from other sorts of Petri nets by the possibility to provide their tokens with a proper structure, which is based on Petri net modelling again. Hence, a net can contain further net items, being able to move around and fire themselves. Motivation Nets within nets are well suited for the modelling of distributed systems under the particular aspects of * hierarchy, * mobility * encapsulation. In a lot of publications in relation to object-oriented design is given, in order to combine the ability of Petri nets in modelling distributed computing with the modelling of objects, being able to be created and to interact. History Starting from the need of practical applications, by the mid of nineties, different formalisms have been created, which fit the description of „nets within nets“. Lomazova and Schnoebelen are listing some of these approaches, namely by Sibertin- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petri Net
A Petri net, also known as a place/transition (PT) net, is one of several mathematical modeling languages for the description of distributed systems. It is a class of discrete event dynamic system. A Petri net is a directed bipartite graph that has two types of elements, places and transitions. Place elements are depicted as white circles and transition elements are depicted as rectangles. A place can contain any number of tokens, depicted as black circles. A transition is enabled if all places connected to it as inputs contain at least one token. Some sources state that Petri nets were invented in August 1939 by Carl Adam Petri—at the age of 13—for the purpose of describing chemical processes. Like industry standards such as UML activity diagrams, Business Process Model and Notation, and event-driven process chains, Petri nets offer a graphical notation for stepwise processes that include choice, iteration, and concurrent execution. Unlike these standards, Petri nets hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object-oriented Design
Object-oriented design (OOD) is the process of planning a system of interacting objects for the purpose of solving a software problem. It is one approach to software design. Overview An object contains encapsulated data and procedures grouped together to represent an entity. The 'object interface' defines how the object can be interacted with. An object-oriented program is described by the interaction of these objects. Object-oriented design is the discipline of defining the objects and their interactions to solve a problem that was identified and documented during object-oriented analysis. What follows is a description of the class-based subset of object-oriented design, which does not include object prototype-based approaches where objects are not typically obtained by instantiating classes but by cloning other (prototype) objects. Object-oriented design is a method of design encompassing the process of object-oriented decomposition and a notation for depicting both logical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coloured Petri Net
Coloured Petri nets are a backward compatible extension of the mathematical concept of Petri net A Petri net, also known as a place/transition (PT) net, is one of several mathematical modeling languages for the description of distributed systems. It is a class of discrete event dynamic system. A Petri net is a directed bipartite graph that ...s. Coloured Petri nets preserve useful properties of Petri nets and at the same time extend the initial formalism to allow the distinction between tokens. Coloured Petri nets allow tokens to have a data value attached to them. This attached data value is called the token color. Although the color can be of arbitrarily complex type, places in coloured Petri nets usually contain tokens of one type. This type is called the color set of the place. Definition 1. A ''net'' is a tuple ''N'' = (''P'', ''T'', ''A'', Σ, ''C'', ''N'', ''E'', ''G'', ''I'' ) where: * ''P'' is a set of ''places''. * ''T'' is a set of ''transitions''. * ''A'' is a set ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rüdiger Valk
Rüdiger Valk (born 5 August 1945) is a German mathematician. From 1976 to 2010 he was Professor for Theoretical Computer Science (Informatics) at the ''Institut für Informatik'' (later ''Fachbereich Informatik'') of the University of Hamburg, Germany.http://www.informatik.uni-hamburg.de/TGI/mitarbeiter/profs/valk_eng.html (accessed 30 July 2013) Valk studied mathematics at the University of Bonn (Germany). Supervised by Wilfried Brauer, he continued studying for a postgraduate degree at Bonn and received his PhD in Mathematics in 1974. In 1976 he became Professor for Theoretical Computer Science (Informatics). From 1985 until 2010 he was head of the research group on theoretical foundations of computer science (Theoretische Grundlagen der Informatik, TGI) at the University of Hamburg. Research career His early research is characterised by work on topological automata and systems,''Discrete and Continuous Realizations of General Time Systems.'' In: ''Journal of Cybernetics.'' 4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reference (programming)
In computer programming, a reference is a value that enables a program to indirectly access a particular data, such as a variable (computer science), variable's value or a record (computer science), record, in the computer's memory (computing), memory or in some other Data storage device, storage device. The reference is said to refer to the datum, and accessing the datum is called Dereference operator, dereferencing the reference. A reference is distinct from the datum itself. A reference is an abstract data type and may be implemented in many ways. Typically, a reference refers to data stored in memory on a given system, and its internal value is the memory address of the data, i.e. a reference is implemented as a Pointer (computer programming), pointer. For this reason a reference is often said to "point to" the data. Other implementations include an offset (difference) between the datum's address and some fixed "base" address, an array index, index, unique key, or identifier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Value Semantics
In computer science, having value semantics (also value-type semantics or copy-by-value semantics) means for an object that only its value counts, not its identity. Immutable objects have value semantics trivially, and in the presence of mutation, an object with value semantics can only be uniquely-referenced at any point in a program. The concepts that are used to explain this concept are extensionality, definiteness, substitutivity of identity, unfoldability, and referential transparency In computer science, referential transparency and referential opacity are properties of parts of computer programs. An expression is called ''referentially transparent'' if it can be replaced with its corresponding value (and vice-versa) withou .... References Programming paradigms {{Compu-prog-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object-oriented Programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of procedures (often known as ''methods''). A common feature of objects is that procedures (or methods) are attached to them and can access and modify the object's data fields. In this brand of OOP, there is usually a special name such as or used to refer to the current object. In OOP, computer programs are designed by making them out of objects that interact with one another. OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types. Many of the most widely used programming languages (such as C++, Java, Python, etc.) are multi-paradigm and they support object-oriented programming to a greater or lesser degree, typically in combination with imper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Method (computer Programming)
A method in object-oriented programming (OOP) is a procedure associated with a message and an object. An object consists of ''state data'' and ''behavior''; these compose an ''interface'', which specifies how the object may be utilized by any of its various consumers. A method is a behavior of an object parametrized by a consumer. Data is represented as properties of the object, and behaviors are represented as methods. For example, a Window object could have methods such as open and close, while its state (whether it is open or closed at any given point in time) would be a property. In class-based programming, methods are defined within a class, and objects are instances of a given class. One of the most important capabilities that a method provides is ''method overriding'' - the same name (e.g., area) can be used for multiple different kinds of classes. This allows the sending objects to invoke behaviors and to delegate the implementation of those behaviors to the receiving o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Model Checking
In computer science, model checking or property checking is a method for checking whether a finite-state model of a system meets a given specification (also known as correctness). This is typically associated with hardware or software systems, where the specification contains liveness requirements (such as avoidance of livelock) as well as safety requirements (such as avoidance of states representing a system crash). In order to solve such a problem algorithmically, both the model of the system and its specification are formulated in some precise mathematical language. To this end, the problem is formulated as a task in logic, namely to check whether a structure satisfies a given logical formula. This general concept applies to many kinds of logic and many kinds of structures. A simple model-checking problem consists of verifying whether a formula in the propositional logic is satisfied by a given structure. Overview Property checking is used for verification when two desc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formal Specification Languages
Formal, formality, informal or informality imply the complying with, or not complying with, some set of requirements (forms, in Ancient Greek). They may refer to: Dress code and events * Formal wear, attire for formal events * Semi-formal attire, attire for semi-formal events * Informal attire, more controlled attire than casual but less than formal * Formal (university), official university dinner, ball or other event * School formal, official school dinner, ball or other event Logic and mathematics *Formal logic, or mathematical logic ** Informal logic, the complement, whose definition and scope is contentious *Formal fallacy, reasoning of invalid structure ** Informal fallacy, the complement *Informal mathematics, also called naïve mathematics *Formal cause, Aristotle's intrinsic, determining cause * Formal power series, a generalization of power series without requiring convergence, used in combinatorics *Formal calculation, a calculation which is systematic, but without a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Models Of Computation
In computer science, and more specifically in computability theory and computational complexity theory, a model of computation is a model which describes how an output of a mathematical function is computed given an input. A model describes how units of computations, memories, and communications are organized. The computational complexity of an algorithm can be measured given a model of computation. Using a model allows studying the performance of algorithms independently of the variations that are specific to particular implementations and specific technology. Models Models of computation can be classified into three categories: sequential models, functional models, and concurrent models. Sequential models Sequential models include: * Finite state machines * Post machines (Post–Turing machines and tag machines). * Pushdown automata * Register machines ** Random-access machines * Turing machines * Decision tree model Functional models Functional models include: * Abstract rew ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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