Dbms classification according to data models

Dbms classification according to data models

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  DBMS CLASSIFICATION ACCORDING TODATA MODELS ABDUL KHALIQ (abdulkhaliq005gis@gmail.com)
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  CLASSIFICATION ACCORDING TODATA MODELS Hierarchal Model Network Model Relational Model Object Oriented model
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  Hierarchical Model In ahierarchical data model, data are organized into a tree-like structure. Use parent/child relationships: • each parent can have many children but • each child only has one parent. • This is called one to many (1:N) relationship
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  • Hierarchical Modelis simple to construct and operate on • Corresponds to a number of natural hierarchically organized domains - e.g., assemblies in manufacturing, personnel organization in companies • Language is simple; uses constructs like GET, GET NEXT, GET NEXT WITHIN PARENT etc. ADVANTAGES: • Navigational and procedural nature of processing • Database is visualized as a linear arrangement of records • Little scope for "query optimization" DISADVANTAGES:
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  Network Model based onan enlargement of the concept of hierarchical data bases. Instead of one single hierarchy, several hierarchical access paths can be provided. In this way, redundancy in the data can be avoided. In contrast to hierarchical data base models • one child node can have more than one father node. Access via the pointers of the network is quite fast whereas access via other attributes becomes inefficient.
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  • Network Modelis able to model complex relationships and represents semantics of add/delete on the relationships. • Can handle most situations for modeling using record types and relationship types. • Language is navigational; uses constructs like FIND, FIND member, FIND owner, FIND NEXT within set, GET etc. Programmers can do optimal navigation through the database. ADVANTAGES: • Navigational and procedural nature of processing • Database contains a complex array of pointers that thread through a set of records. Little scope for automated "query optimization DISADVANTAGES:
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  Relational Model (RDBMS) Data arestored in tables. Its rows contain objects of identical type; Columns describe the attributes of each of the instances of the object. Queries to a relational data base are formulated in a query language, for instance in SQL (Structure Query Language). Tables can be modified or combined by several operations of relational algebra
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  • Data basequeries are based on a comparison of the table contents. • The tables are independent and not related by pointers. That is why it is easy to maintain dynamic data sets. • The tables can be easily expanded by new columns. • It is easy to create user specific views from relational data bases. Advantages • Slower access rates compared to hierarchical or network based data bases. Faster access rates can be achieved by the indexing techniques which, however, require additional disk space. • Access to spatial data by geometrical attributes is not optimal. Disadvantages
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  Object Oriented Model (ODBMS) Objectoriented data base systems are the most recent development in data base technology. Goal: to offer more complex data Define a database in terms of object • Objects are consist of properties and operations (procedures) • Objects with same property and operation are belong to one class • Classes are organized into hierarchies Extends Relational Model to include • Objects / Structured Type • Methods defined for object • Ability of one tuple to refer to another through reference type
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  • The object-orienteddata model allows the 'real world' to be modeled more closely. • It new data types to be built from existing types. • The tight coupling between data and applications in an OODBMS makes schema evolution more feasible. Advantages • There is a general lack of standards of OODBMS. • Query optimization requires.Disadvantages