Types of models •
Database model A database model is a theory or specification describing how a database is structured and used. Several such models have been suggested. Common models include
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Flat model Hierarchical Hierarchical model Network model Relational model Object-relational Object-relational model Concept Oriented Model Star schema
Data Structure Diagram A data structure diagram (DSD) is a diagram and data model used to describe conceptua conceptuall data models models by providin providing g graphica graphicall notation notations s which which document document entities entities and their relations relationships hips,, and the constraints constraints that binds binds them. them. The basic graphic elements of DSDs are boxes, representing entities, and arrows, repres represent enting ing relati relations onship hips. s. Data Data struct structure ure diagra diagrams ms are are most most usefu usefull for documenting complex data entities.
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Entity-relationship Entity-relationship model An enti entity ty-r -rel elat atio ions nshi hip p mode modell is an abst abstra ract ct conc concep eptu tual al data data mode modell (or (or semantic data model) used in software engineering to represent structured data. Entity relationship models (ERMs) produce a conceptual data model of a system system,, and its requir requirem ement ents s in a top-do top-down wn fashio fashion. n. There There are are severa severall notations for data modeling. The actual model is frequently called "Entity relati relations onship hip model" model",, becaus because e it depic depicts ts data data in terms terms of the entiti entities es and relationships described described in the data.
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Geographic data model A data model in Geographic information systems is a mathematical construct for representing geographic objects or surfaces as data. For example, the vector data model represents geography as collections of points, lines, and polygons; the raster data model represent geography as cell matrixes that store store numeri numeric c values values;; and the the Triang Triangula ulated ted irreg irregula ularr networ network k (TIN) (TIN) data data model represents geography as sets of contiguous, non-overlapping non-overlapping triangles.
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Generic data model These models are generalizations of conventional data models. They define standardized general relation types, together with the kinds of things that may be related by such a relation type. Generic data models are developed as an approach to solve some shortcomings of conventional data models. For example, example, differen differentt modelers modelers usually usually produce produce differen differentt conventio conventional nal data models of the same domain. This can lead to difficulty in bringing the models of different people together and is an obstacle for data exchange and data integrati integration. on. Invariab Invariably, ly, however, however, this differenc difference e is attributa attributable ble to different different
levels of abstraction in the models and differences in the kinds of facts that can be instantiated (the semantic expression capabilities of the models). The modelers need to communicate and agree on certain elements which are to be rend render ered ed more more conc concre rete tely ly,, in orde orderr to make ake the the diff differ eren ence ces s less less significant. •
Semantic data model A semantic data model in software engineering is a technique to define the meaning of data within the context of its interrelationships with other data. A semantic data model is an abstraction which defines how the stored symbols rela relate te to the the real real worl world. d. A sema semant ntic ic data data mode modell is some someti time mes s call called ed a conceptual data model.
More Related models •
Data flow diagram A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system. It differs from the flowchart as it shows the data flow instead of the control flow of the program. A data flow diagram can also be used for the visualization of data processing (structured design). Data flow diagrams were invented by Larry Constantine, the original developer of structured design, based on Martin and Estrin's "data flow graph" model of computation. computation. It is common practice to draw a context-level Data flow diagram first which shows the interaction between the system and outside entities. The DFD is designed to show how a system is divided into smaller portions and to highlight the flow of data between those parts. This context-level Data flow diagram is then "exploded" to show more detail of the system being modeled.
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Information model An Information model is not a type of data model, but more or less an alternative model. Within the field of software engineering both a data model and an information model can be abstract, formal representations of entity types that includes their properties, relationships and the operations that can be performed on them. The entity types in the model may be kinds of realworld objects, such as devices in a network, or they may themselves be abstract, such as for the entities used in a billing system. Typically, they are used to model a constrained domain that can be described by a closed set of entity types, properties, properties, relationships relationships and operations.
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Object model
An object model in computer science is a collection of objects or classes through which a program can examine and manipulate some specific parts of its world. In other words, the object-oriented interface to some service or system is said to be the object model of the represented service or system. For example, the Document Object Model (DOM) is a collection of objects that represent a page in a web browser, used by script programs to examine and dynamically change the page. E.g., there is a Microsoft Excel object model for controlling Microsoft Excel from another program. •
Object Role Model Object Role Modeling (ORM) is a method for conceptual modeling, and can be used as a tool for information and rules analysis. Object Role Modeling is a fact-oriented method for performing systems analysis at the conceptual level. The quality of a database application depends critically on its design. To help ensur ensure e correc correctne tness ss,, clarit clarity, y, adapta adaptabil bility ity and produ producti ctivit vity, y, infor informa matio tion n systems are best specified first at the conceptual level, using concepts and language that people can readily understand.
OR Models Applying Applying the operation operations s research research and managem management ent science science (OR/MS) (OR/MS) models models to solve solve manag manageri erial al probl problems ems has gained gained in popula popularit rity y as the the compu computin ting g power power advanc advances es and more more compu computer ter syste systems ms are design designed ed for assis assistin ting g the usage usage of OR/MS models. Many of these systems are designed with one specific model in mind, for example, linear programming or the EOQ model. Due to their lack of versatility, users have to know which OR/MS model to use in order to choose the right package. Thus, these systems usually provide nothing more than speeding up the process from getting inputs to a model through outputs generated.
