- Modeling perspectives
Modeling perspectives is a set of different ways to represent pre-selected aspects of a system. Each
perspectivehas a different focus, conceptualization, dedication and visualization of what the modelis representing.
In information systems, the traditional way to distinction between modeling perspectives is structural, functional and behavioral/processual perspectives. This together with rule, object, communication and actor and role perspectives is one way of classifying modeling approaches [ [http://www.idi.ntnu.no/~krogstie/publications/2003/quality-book/b2-languages.pdf Conceptual modeling] , John Krogstie, 2003 ] .
tructural modeling perspective
This approach concentrates on describing the static structure. The main concept in this modeling perspective is the entity, this could be an object, phenomena, concept, thing etc.
The data modeling languages have traditionally handled this perspective, examples of such being:
*The ER-language (Entity-Relationship)
*Generic Semantic Modeling language (GSM)
*Other approaches including::*The NIAM language (Binary relationship language):*Conceptual graphs (Sowa)
Looking at the ER-language we have the basic components:
*Entities: Distinctively identifiable phenomenon.
*Relationships: An association among the entities.
*Attributes: Used to give value to a property of an entity/relationship.
Looking at the generic semantic modeling language we have the basic components:
*Constructed types built by abstraction: Aggregation, generalization, and association.
*Primitive types: Data types in GSM are classified into printable and abstract types.:*Printable: Used to specify visible values.:*Abstract: Representing entities.
Functional modeling perspective
This approach concentrates on describing the dynamic process. The main concept in this modeling perspective is the process, this could be a function, transformation, activity, action, task etc. A well-known example of a modeling language employing this perspective is data flow diagrams.
The perspective uses four symbols to describe a process, these being:
*Process: Illustrates transformation from input to output.
*Store: Data-collection or some sort of material.
*Flow: Movement of data or material in the process.
*External Entity: External to the modeled system, but interacts with it.
Now, with these symbols, a process can be represented as a network of these symbols.This decomposed process is a DFD, data flow diagram.
Behavioral perspective gives a description of system dynamics. The main concepts in behavioral perspective are states and transitions between states. State transitions are triggered by events. State Transition Diagrams (STD/STM), State charts and Petri-nets are some examples of well-known behaviorally oriented modeling languages. Different types of State Transition Diagrams are used particularly within
real-time systemsand telecommunicationssystems.
Rule perspective gives a description of goals/means connections. The main concepts in rule perspective are rule, goal and constraint. A rule is something that influences the actions of a set of actors. The standard form of rule is “IF condition THEN action/expression”. Rule hierarchies (goal-oriented modeling), Tempora and Expert systems are some examples of rule oriented modeling.
The object-oriented perspective describes the world as autonomous, communicating objects. An object is an “entity” which has a unique and unchangeable identifier and a local state consisting of a collection of attributes with assignable values. The state can only be manipulated with a set of methods defined on the object. The value of the state can only be accessed by sending a message to the object to call on one of its methods. An event is when an operation is being triggered by receiving a message, and the trace of the events during the existence of the object is called the object’s life cycle or the process of an object. Several objects that share the same definitions of attributes and operations can be parts of an object class. The perspective is originally based on design and programming of oriented systems.
Unified Modelling Language(UML) is a well known language for modelling with an object perspective.
This perspective is based on language/action theory from
philosophical linguistics. The basic assumption in this perspective is that person/objects cooperate on a process/action thorough communication within them.
An illocutionary act consists of five elements: Speaker, hearer, time, location and circumstances. It is a reason and goal for the communication, where the participations in a communication act is oriented towards mutual agreement. In a communication act, the speaker generally can raise three claims: truth (referring an object), justice (referring a social world of the participations) and claim to sincerity (referring the subjective world of the speaker).
Actor and role perspective
Actorand roleperspective is a description of organisational and system structure. An actor can be defined as a phenomenon that influences the history of another actor, whereas a role can be defined as the behaviour which is expected by an actor, amongst other actors, when filling the role. Modelling within these perspectives is based both on work with object-oriented programming languages and work with intelligent agents in artificial intelligence. I*is an example of an actor oriented language.
Integrated multi-perspective modeling
In the systemic
goal-orientedconceptual modeling of complex abstract and real world systems, the perspectives have to be ordered and can be decomposed/specialized according to selected points of view. An example of integrated multi-perspective modeling is the Top-down Object-based Goal-oriented Approach (TOGA meta-theory) [ [http://188.8.131.52/wwwerg26701/Gad-toga.htm TOGA meta-theory] Adam Maria Gadomski, 1993 ] . It assumes the initial subjectiveperspective of an intelligent agentwhich can be a modeler, problem solver or designer. The agent perspective depends on its/his capacityof conceptualization, and available:"information", "preferences" and "knowledge" (IPK model). During the goal-oriented modeling activity, the initial perspective is specialized, using an object-based framework for the top-down modeling of: "systems", "processes", "functions" and "design- goals". In the case of intelligent entities (in the agent domain of activity), their specification/identificationis performed in terms of formally linked: "intervention-goal", "tasks" and "actions". Every perspective is characterized by the following spatial-metaphoric meta-attributes:
* conceptualization distance
* conceptualization angle
* observation tool
* activity tool range.
Model Driven Engineering(MDE)
Glossary of Unified Modeling Language terms
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