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Sep 5, 2010

Data Model


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Data model is a description of the organization of data in a database, it describe the relationship between data and any constraint.  It can be used for variety of purpose from high-level conceptual models to physical data models. It is similar to class modeling from the application developer view’s, but data modeling is little bit different because it focus on data only. Data models do not include unstructured data such as email messages, word processing documents, digital video, audio or image files.
Type:
  1. Conceptual Data Modeling
  2. Logical Database Modeling 



      1. Object Based logical Model
      2. Record Based logical Model
  3. Physical Database Modeling



Conceptual Data Modeling: It provides very high level abstract data model and works very close to user’s view of the world. It provides a project-level view of the business data. It suppresses technical details by including the entities that have a business meaning, the important relationships between these entities and the major attributes of the entities. The advantage is that the notation is very simple, something your project stakeholders can quickly grasp, although the disadvantage is that the models become large very quickly. More Details
Logical Database Modeling: It describe the data and their relationship in detail as much as possible without knowing how they will be implemented physically. LDM involves the process of constructing a model of information but independent of a particular DBMS.  Logical modeling involves gathering information about business processes, business entities (categories of data), and organizational units. After this information is gathered, diagrams and reports are produced including entity relationship diagrams, business process diagrams, and eventually process flow diagrams. ER(Entity relationship diagram) is a most commonly know tool for LDM.
Physical Database Modeling: It Includes the complete database artifact for example table, indexes, relationship, properties, constraint definitions, linking tables.Physical modeling deals with the conversion of the logical, or business model, into a relational database model. When physical modeling occurs, objects are being defined at the schema level.  Majorly we have Oracle, SQL Server, DB2, Solaris. SQL server runs only on Microsoft platform and good for small enterprise level application, Both Oracle and MySql runs windows as well Unix, Linux and Solaris environments. So the Physical database design will be based on the database selected by end user. More Details. Server Design diagram, Database design documentations are the main deliverables of PDM.

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