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Data models


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Data models

  1. 1. ASSIGNMENT#1 DATA MODELSData Model: “ An integrated collection of concepts for describing and manipulating data, Relationships between data,and constraints on the data in an organization.”A database model is a theory or specification describing how a database is structured and used.Several such models have been suggested.A data model is not just a way of structuring data: italso defines a set of operations that can be performed on the data.Some common modelsincludes: Flat File Model Hierarchal Model Network Model Relational Model Object Relational Model Object based model(Entity Relationship) Flat File Model:The flat (or table) model consists of a single, two-dimensional array of data elements, where allmembers of a given column are assumed to be similar values, and all members of a row areassumed to be related to one another. For instance, columns for name and password that might beused as a part of a system security database. Each row would have the specific passwordassociated with an individual user. Columns of the table often have a type associated with them,defining them as character data, date or time information, integers, or floatingHow It WorksTo make a flat file data model functional, all relevant information about a record needs to bestored in the same file. In a CSV sheet, for example, no application-specific formats apply to thedata contained within the file; only a comma denotes the end of one field in a record. Eachrecord is written on a line in the file, allowing all data for a single record to be stored separatelyfrom other records.DATABASE SYSTEM Page 1
  2. 2. ASSIGNMENT#1Such databases can quickly become very large and difficult to manage because of the simple waythey are organized. Many modern data models use connected tables to organize groups of relateddata. This makes such information easier to locate and more flexible to work with/Flat File Data Model At File Data Model Contains A Single Structure, Two-Dimensional Array of Data Elements Representing One Specific Business Area. All The Members of A Given Column in The Two-Dimensional Array Are Assumed To Contain Similar Values of Same Data type All Members of A Row Are Assumed To Be Related To One Another As Per The Business Requirements.Advantages Flat File Database is Simple To Develop And Easy To Implement Can Be Considered For Small Databases With Small Business Units We Can Avail The Locking Facilities Provided By The Operating System Locking ConceptsDis-Advantages Cannot Control The Data Redundancy Transactional Management Can Be A Big Head-Ache Concurrency Management Can Be A Big Bottle Neck As The Number of Clients Increase Flat File Database is A Big Botheration For Storage As it can Be Stored And Operated From Only One Location Flat File Databases Are Very Critical To Recover When Corrupted.11/8/2012DATABASE SYSTEM Page 2
  3. 3. ASSIGNMENT#1Object Relational Model:The object relational model is designed to provide a relational database management that allowsdevelopers to integrate databases with their data type and methods. It is essentially a relational modelthat allows users to integrate object-oriented features into it.Functions: The main function of the object relational model is to combine the convenience of therelational model with the object model.The benefit of this combination range from scalability tosup port for rich data type.The primary function of this model is to morepower,greater flexibility,better performance and greaterdata integrity than those that comes before it.The objectrelationsl model allow the users to define datatype,function and also operators.As a direct result of thisfunctionality and performance of this model areoptimized.It can be said that obeject relational model isan evolutionary technology this approach has taken onthe roubust trabsuction and performance managementaspect of its predeccesser.Advantages: Some of the benefits that are offered by the object relational model include: Extensibility: Users are able to extended the capability of the database . Complex Types: It allow users to define new data type that combine one or more of the current existing data types. Inheritance: Users able to define object or type and table that procur the properties of other object as well as new properties that are specific to the oject that has been defined.The object relational database management system(ORDMS) these system provide an additionof new and extensive object storage,capability to the relational model and the centre of the moremodern information system of today. Object-Relational Data Models Add New Object Storage Capabilities To The Relational Systems At The Core of Modern Information Systems. The Object-Relational Data Models Provide New Facilities To Integrate Traditional Business Data With Complex Objects Such As Time-Series And Geospatial Data. The Object Relational Data Models Provide Features Like o Type Constructor For Objects And Object Types o Object Identity And References o Collection Type Constructors For Nested Tables And Complex ObjectsDATABASE SYSTEM Page 3
  4. 4. ASSIGNMENT#1 o Reference Type Constructor o Methods For Object Types o Object Tables (Object relational model)Object-based Model: “Object based data model use concepts such as entities,attributes and relationships.”Object-based logical models:Describe data at the conceptual and view levels. o Provide fairly flexible structuring capabilities. o Allow one to specify data constraints explicitly. o Over 30 such models, including:  Entity-relationship model.  Object-oriented model.  Binary model.  Semantic data. Entity-Relationship ModelThe Entity-Relationship (ER) model, a high-level data model that is useful in developing aconceptual design for a database. In 1976, Chen developed the Entity-Relationship (ER)model, a high-level data model that is useful in developing a conceptual design for a database.DATABASE SYSTEM Page 4
  5. 5. ASSIGNMENT#1Creation of an ER diagram, which is one of the first steps in designing a database, helps thedesigner(s) to understand and to specify the desired components of the database and therelationships among those components. An ER model is a diagram containing entities or "items",relationships among them, and attributes of the entities and the relationships. EntityAn entity is a real-world item or concept that exists on its own. The set of all possible values foran entity is the entity type.. In our example, a particular student , team, lab section, or experiment is an entity. The set of allpossible values for an entity, such as all possible students, is the entity type. In an ER model, wediagram an entity type as a rectangle containing the type name, such as student. AttributeAn attribute of an entity is a particular property that describes the entity. The set of all possiblevalues of an attribute is the attribute domain.Each entity has attributes, or particular properties that describe the entity. For example, studentshas properties of his own Student Identification number, name, and grade. A particular value ofan attribute, such as 93 for the grade, is a value of the attribute. Most of the data in a databaseconsists of values of attributes. The set of all possible values of an attribute, such as integersfrom 0 to 100 for a grade, is the attribute domain.A simple attribute is one component that is atomic. A composite attribute has multiplecomponents, each of which is atomic or composite..DATABASE SYSTEM Page 5
  6. 6. ASSIGNMENT#1 RelationshipA relationship type is a set of associations among entity types. A relationship or relationshipinstance is an ordered pair consisting of particular related entities. For example, the studententity type is related to the team entity type because each student is a member of a team.DATABASE SYSTEM Page 6
  7. 7. ASSIGNMENT#1Types of Relationships in ER model:1-One-to-OneConsider the example of a university.For one Department there can be only one departmenthead.This is one-to-one relationship.2-One-to-Many:A STUDENT can MAJOR in only one course,but many STUDENTs would have registered for agiven MAJOR course.This is one-to-many relationship..3-Many-to-Many:A STUDENT can make many coursesand many STUDENTs can registered for a givenCOURSE.This is called many-to-many relationship.DATABASE SYSTEM Page 7
  8. 8. ASSIGNMENT#1Refrences: . e1.htmldelling/. http://woffor SYSTEM Page 8