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Database Management Systems An Evaluation of the Property-4-R-Us real estate agency case
Database Management Systems: An Evaluation of the Property-4-R-Us real estate agency’s case
Omari Simba
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Table of Contents
TOC o “1-3” h z u Introduction PAGEREF _Toc385800798 h 3Different DBMS approaches and the actual DBMS employing them PAGEREF _Toc385800799 h 3File System Approach to data storage PAGEREF _Toc385800800 h 4Relational Database Management Systems (RDBMS) PAGEREF _Toc385800801 h 4Object-Oriented Database Management System Approach PAGEREF _Toc385800802 h 5Object-Relational Database Management System (ORDMS) approach PAGEREF _Toc385800803 h 5Other Database Management Systems PAGEREF _Toc385800804 h 6Conclusion PAGEREF _Toc385800805 h 6Entity relationship diagram (ERD), identifying entities in the problem domain and showing relationships among entities7Identifying entities and their attributes7Entity Agent7Entity Client8Entity Property9Relationship Among Entities9Deriving Entity Relationships9Entity Relationships10Entity Relationship Diagram11Relational Model of ERD12 Creating and populating tables property, entity and agent………………………………..13
References17
Introduction Many organizations are rapidly embracing management information systems as opposed to the traditional off-the-shelf filing, prompting an urgent rise for the need of data warehousing. The data fed into the management information systems and the information produced as the processed data need to be stored for future retrieval, aid in further data processing and act as future reference. Data can be stored in various forms in the computer. However, the file system and the database system approaches are the main forms of data storage mechanisms. The efficient mechanism for data storage among the two is the database system. A database is a collection of real-world related data, collected and maintained to represent a given organisation’s information needs (Kumar, N.d, p. 2). The users can interact with the database by creating and maintaining its data through the database management system which is simply a set of programs that provides abstraction between the database and the user (Robbins, 1995, p. 3). Different database management systems (DBMS) are in existence, employing the Relational database approach, Object-oriented database approach, object-relational approach or the file system approach.Different DBMS approaches and the actual DBMS employing them
Every actual database management system implementation has a theory of operation behind it. The theory models and simulates the way data is stored and manipulated through update, search, insertion, deletion and retrieval. The theory lays down the framework for the operation of the entire database management system. It is important therefore to explore the various theories that have been advanced to simulate the working of the various database management systems.
In any one specific approach, the following requirements must be met to qualify that given database management system as effective: efficiency should be met in manipulation of very large data, fault-tolerance and resilience in case of hardware or software failure without inconsistence and loss of data, capability to incorporate access control mechanisms to allow only authorized personnel to access it, have a long perseverance ability transcending time and nature of programs accessing its contents (Sirpal, N.d, P.4).
File System Approach to data storage
The file system is part of the operating system that manages the storage, manipulation and retrieval of files. The files are records of interrelated data/information. However, the file system has been found to have the following main flaw: data redundancy.
Relational Database Management Systems (RDBMS)
In relational database management systems, the stored data is modelled into relations that exist between attributes of entities, which are real world objects. The attributes of that given entity is represented in the columns while the instance of the entity representing the real world object is represented by the records; rows of the table. According to Bergholt et al (1998), a relational database management system is a system that organizes data/information into two-dimensional relations as represented in the rows and columns of the database table (p.11). The record, also known as a tuple, contains information about a given instance of an entity with the component of each cell being of a primitive data type; integer (int), character (char), float, strings. (Subau, 2007, p.2). The RDBMS is advantageous in that it provides an easier approach in the analysis, design, implementation, testing, maintenance and use of the database, excellent conceptual simplification, excellent SQL querying ability which in combination produces an efficient database management system (Sirpal, N.d, p.30). It however has the following advantages: lack of enough space to handle the storage of media files like audio and visual files, the restriction of data being stored in rows and columns and poor design possibility (Sirpal. N.d, P. 30).
Object-Oriented Database Management System ApproachAccording to Bergholt et al (1998) the entity in the RDMS is modelled to be an object in the OODBMS, having the attributes of procedures, a group of values or simple values and pointers/references to other objects (p. 15). Data is stored along with those procedures that can act on that data (Subau, 2007, p.3). Structural properties and Behavioural properties of an object are defined by a finite set of attributes and finite set of methods that are uniquely inherent in any particular object ( Wang, N.d, p. 6). The OODBMS was designed to handle complex and large data while ensuring consistent, secure, extensible and controlled data management, controlled and extensible data management, data independent mechanisms that would allow the implementation of the object-oriented model of database design (Sirpal, N.d, p. 31). The theory also inherits other powerful object-oriented language capabilities like data encapsulation, inheritance, polymorphism and use of objects to represent real world entities, making it better than RDBMS (Sirpal, N.d, p.31).
Object-Relational Database Management System (ORDMS) approach
The object-relational approach is an attempt to extend the functionalities of relational database managements (RDBMS) systems with the object-oriented approach of database design by attempting to bridge the gap between the two (Wang, N.d, p. 4). Both features from the two approaches must be combines to produce a real ORDBMS (Bergholt et al., 1998).
Other Database Management Systems
Apart from the three main database design approaches discussed above, other minor database design theories have been advanced. Güting (1994) proposes a spatial database model system that supports spatial data types and querying languages to achieve spatial join methods and indexing suitable for geographic information system applications (p. 1). Parallel and distributed database management systems have also been proposed. Parallelism achieved through partition and pipelining techniques have proven to achieve database access efficiency through indexing, querying and data loading experimental techniques (Ramakrishnan et al. 1992). Combining parallelism in a distributed environment can highly increase the efficiency of access to any distributed DBMS.
Conclusion
Object-Relational approach to database management system design proves to be the most efficient design mechanism for the database management system in our case. To improve it further, aspects of spatial, parallelism and distributed computing environments can be added to the database management system to make it more efficient to handle virtually any data, from any geographical area in an efficient manner. A spatial distributed parallel ORDMS can be proposed to be deployed in managing the data warehousing needs of Property-4-R-Us real estate agency. Entity relationship diagram (ERD), identifying entities in the problem domain and showing relationships among entitiesIdentifying entities and their attributesEntity Agentagent_id
Commission_rate
W_phone
M_phone
l-name
surname
f-name
Commission_code
Agent_contacts
Agent
Agent_name
total_monthly_sales
base_salary
payment_date
cheque_number
Client_id
Entity Client
Client-id
First_name
property_id
client_phone
mobile-phone
last_name
surname
Client
Client-type
address
Entity PropertyProperty_id
location
Agreed_price
listingForSale_date
Year_build
size
Asking_price
House_design
Property
Buyer_id
buter
Deposit_paid
Settlement_date
room_numbers
Relationship Among EntitiesDeriving Entity RelationshipsAgent Property Client
Agent Values Pays/Receives-payment
Property valued Sold/bought
Client Books appointment Buys/sells Entity RelationshipsAgent
Values
Property
Client
Agent
Property
Agent
Valued
Pays or Paid
Book Appoint
Client
Agent
Client
Buys/Sells
Bought/sold
Property
Client
Property
Entity Relationship DiagramA_name
agent_id
chequeNo
client_id
No.Rms
Yr_build
H_design
ListDate
totalMonthsales
BaseSalary
SettlementDate
description
AgreePrice
phone
Client_id
Pro_id
Address
mobile
f_name
surname
l_name
C_type
Address
rate
Mobile
payDate
Pro_id
Deposit
AskPrice
size
location
Paid/pays/Book Appointment
Client
Buys/sells/bought/sold
Property
Valued/Values
Agent
Relational Model of ERDProperty Property_id (PK) Size Location Description House_design NumberOfRooms Year_build ListingForSale_date Asking_price Agreed_price Deposit_paid Settlement_Date Agent_id (FK) Client_id (FK)
Agent Agent_id (PK) f_name surname l_name work_phone mobile_phone Cheque_number Payment_date Base_salary Commission_code Commission_rate Total_Monthly_salary client_id (FK)
Pays or Paid/ Book Appointme
Buys or Sells/Bought
Values/Valued
Client Client_id (PK) Client_type f_name surname l_name Mobile_phone Telephone Postal_Address Physical_address Property_id (FK)
3. Creating and Populating tables agent, client and property
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/*!40101 SET NAMES utf8 */;
— Database: `pr4u`
CREATE DATABASE IF NOT EXISTS `pr4u` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci;
USE `pr4u`;
/* Table structure for table `agent`*/
CREATE TABLE IF NOT EXISTS `agent` (
`agent_id` varchar(20) NOT NULL,
`f_name` varchar(20) NOT NULL,
`surname` varchar(20) NOT NULL,
`l_name` varchar(25) NOT NULL,
`work_phone` int(25) NOT NULL,
`mobile_phone` int(20) NOT NULL,
`base_salary` int(20) NOT NULL,
`total_monthly_sales` int(25) NOT NULL,
`commission_code` varchar(20) NOT NULL,
`commission_rate` int(25) NOT NULL,
`cheque_number` varchar(25) NOT NULL,
`payment_date` varchar(25) NOT NULL,
`client_id` varchar(25) NOT NULL,
PRIMARY KEY (`agent_id`),
KEY `client_id` (`client_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
/*Populating table ‘agent’*/
INSERT INTO `agent` (`agent_id`, `f_name`, `surname`, `l_name`, `work_phone`, `mobile_phone`, `base_salary`, `total_monthly_sales`, `commission_code`, `commission_rate`, `cheque_number`, `payment_date`, `client_id`) VALUES
(‘A1’, ‘John’, ‘Smith’, ‘Clark’, 2012181205, 712181205, 800, 500000, ‘A’, 0, ‘A1C3245′, ’10/04/2014’, ”),
(‘A2’, ‘Sussan’, ‘Jane’, ‘Doe’, 202568978, 714559860, 1000, 800000, ‘C’, 0, ‘A2C4586′, ’30/04/2014’, ‘C1’),
(‘A3’, ‘Mathews’, ‘Ken’, ‘Johnstone ‘, 208579369, 832569875, 12000, 1000000, ‘D’, 0, ‘A3C4587′, ’29/04/2014’, ‘C1’);
/* Table structure for table `client`*/
CREATE TABLE IF NOT EXISTS `client` (
`client_id` varchar(20) NOT NULL,
`f_name` varchar(20) NOT NULL,
`surname` varchar(20) NOT NULL,
`l_name` varchar(20) NOT NULL,
`client_type` varchar(10) NOT NULL,
`mobile_phone` int(20) NOT NULL,
`home_phone` int(20) NOT NULL,
`address` int(20) NOT NULL,
`city` varchar(20) NOT NULL,
`property_id` varchar(20) NOT NULL,
KEY `property_id` (`property_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
—
/*Populating table ‘client’*/
—
INSERT INTO `client` (`client_id`, `f_name`, `surname`, `l_name`, `client_type`, `mobile_phone`, `home_phone`, `address`, `city`, `property_id`) VALUES
(‘C1’, ‘Richard’, ‘Klein’, ‘Joe’, ‘Seller’, 2147483647, 2147483647, 40325, ‘Liverpool’, ‘P5’),
(‘C2’, ‘Annette’, ‘Mary’, ‘Wycliffe’, ‘Buyer’, 23569856, 35687927, 4543256, ‘London’, ‘P3’);
/*Table structure for table `property`*/
CREATE TABLE IF NOT EXISTS `property` (
`property_id` varchar(20) NOT NULL,
`location` varchar(20) NOT NULL,
`size` int(10) NOT NULL,
`house_design` varchar(20) NOT NULL,
`deposit_paid` int(20) NOT NULL,
`settlement_date` date NOT NULL,
`room_numbers` int(20) NOT NULL,
`year_build` date NOT NULL,
`listing_year` date NOT NULL,
`asking_price` int(25) NOT NULL,
`agreed_price` int(25) NOT NULL,
PRIMARY KEY (`property_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
/*Populating table ‘property’*/
INSERT INTO `property` (`property_id`, `location`, `size`, `house_design`, `deposit_paid`, `settlement_date`, `room_numbers`, `year_build`, `listing_year`, `asking_price`, `agreed_price`) VALUES
(‘P1’, ‘London’, 0, ‘Bungalow’, 50000, ‘2014-04-30’, 3, ‘2010-12-15’, ‘2014-04-01’, 200000, 150000),
(‘P2’, ‘Birmigham’, 0, ‘Apartment’, 100000, ‘2014-04-29’, 30, ‘2012-08-16’, ‘2014-02-04’, 1000000, 850000);
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
ReferencesKumar, PS. N.d. Database Systems
Robbins, RJ. (1995). Database Fundamentals. Johns Hopkins University
Sirpal, S. N.d. Intro to RDBMS-OODBMS-ORDBMS
Bergholt, L., Due, JS., Hohn, RT., Knudsen, JL., Nielsen, KH., Olesen, TS. & Pedersen, ES. (1998). Database Management Systems: Relational, Object-Relational, and Object-Oriented Data Models, Centre for Objekt Teknology
Subau, G. (2007). Comparison of RDBMS, OODBMS and ORDBMS, Bucharest, Romania
Wang, LT. N.d. Object-Oriented DBMS Concepts, National University of Singapore
Güting, RH. (1994). An Introduction to Spatial Database Systems
Ramakrishnan, Gehrke, Hellerstein & Gray.(1992). Parallel Database Systems: The Future of High Performance Database Systems.
Conducting a Needs Assessment
Conducting a Needs Assessment
Name
Date
Conducting a Needs Assessment
The primary goal for any business enterprise is to make the maximum possible amount of profit. Hence, it is upon the management to carry out a careful market analysis, identify the product to produce, plan the operations and provide the required resources. My concern is to carry out a need analysis in the sales support call centre.
This department which consists of 25 employees was to be in charge of coordinating the operations of sales and marketing executives in the field. They were to offer communication and provide a possible linkage between them and the potential clients. Moreover, they were to be in charge of the newly created online marketing department. However, throughout my analysis, I established that this has not been accomplished because the department has been blamed for incompetency. They do not adequately support the executives especially those in foreign assignments. Besides, they are not courteous to the clientele. In fact, they have been reported to be rude and incompetent in answering important questions regarding the organization and its products. This has led to a sharp decline in the stock turn over (Robinson, D.G. & Robinson, J.C., 2005).
Based on the above inefficiencies, I would like to suggest to the top management especially, the Human Resource Department to take the appropriate measures. First, the 25 workers should be given more training on how best they can improve their performance. This should be done by organizing for seminars, conferences and workshops. Here, they should be lectured on basics of communication skills and how it can be effectively used to reconstruct the company’s injured reputation. On the other hand, the work force may be increased by recruiting more staff to this department (Kaufman, R.A., 2003). They should be highly qualified and given additional orientations before beginning the job.
In conclusion, I would like to point out that communication is the most sensitive part of any organization. It should be staffed by appropriately trained personnel whose performance should be closely monitored and constantly improved through motivation and periodical inductions. This will help in bridging such disparities.
References
Kaufman, R.A. (2003). Needs Assessment: A User’s Guide. Englewood Cliffs, New Jersey:
Educational Technology Publications, Inc.Robinson, D.G. & Robinson, J.C. (2005). Performance consulting: Moving beyond training. San
Francisco: Berrett-Koehler.
Database Differentiation Matrix
Database Differentiation Matrix
Part 1
Using the table below, choose five different data models, describe each model, describe the similarities and differences between the models, and describe the functions of each model. Your responses should total 1,050 to 1,400 words.
Data Model Description Similarities and Differences Function
Network Model This is a data model for data that is naturally modeled to have more than one parent per individual child. This model allows the modeling of multiple related data. It provides for many relationships.
The network model was defined during the Conference on Data Systems Languages, held in 1971. During the conference the model was discussed and approved as a data model.
In the network model, the basic unit is a set. The set is made up of a set name, the owner record type and member record type.
The multi relationships are conceptualized when a member record type has the same role in multiple sets. The main difference of the network model from other models is that there may be one to many and many to many relationships between the records.
It is similar to other data models since it is able to organize data into records and sets. Used where a flexible relationship between objects needs to be showcased.
Hierarchical Model The hierarchical model is a model that arranges data in a tree structure. There is one initial source, the parent, which can have many children. It is presented in a structure that resembles a tree. The only relationship that is represented in this data model is the one-to-many relationship. A child has only one parent, but a parent has several children, represented as branches off the parent in a diagram.
The representation of a hierarchical model is similar to a table, where records are equivalent to rows, while attributes are equivalent to columns.
The hierarchical model is the first model to be used by IBM in designing database systems.
Mappings for this model can be represented as 1: N, a representation for one to many.
Similar to the network model, one-to-many relationships are used. Meaning that a parent can have many children, but a child can only have on parent.
It is the only data model that uses the passing on of 1: N mappings.
This model was used in creation of databases by IBM before other data models were designed. It is used where flexibility is not needed in the design and implementation of a database system.
Object relational model It is a data model closely related to the relational model however it stands out by implementing object oriented concepts. This involves the use of inheritance and encapsulation among other concepts that are used in the object oriented design. It also entails use of classes and objects. This model supports data types which have been customized together with the use of methods.
This model assimilates characteristics of both relational model and object oriented model.
In this model, data is stored in a database, and using the query language, the data can be changed and stored in a new model. Similar to the relational model, data is stored in a database. The data which is stored in a database can be manipulated using a query language. Similar to object oriented model this model view a database as an object where programs written in object oriented languages are stored. The model is used to store data in a database, data which is changeable. Used where a model which integrates the relational model concepts with object oriented concepts.
Relational model This is a database management model which mathematically describes how data is structured. This model primarily bases its concepts on the first order predicate logic. It was designed and implemented first by Edgar Codd in 1969.
In this model, tuples is the term that is used to refer to data. Representation of data is in tuples. The data is also grouped into relations.
The main intention of using this model is to have the specifying data and queries declared in the model.
This way, a user can easily search for information in the database, by clearly stating what they require then let the software managing the database handle the process of retrieving the searched data item. This way a user has little input in the process of searching, only feeding a query and leaving the rest to the database management software.
This model is implemented mainly using the standard query language to define data and make searches through the database. In this model, records which are related are connected together using a “key”, unlike in other models.
The model has logic for dealing with searches, known as the three-valued logic, after a search, you either get a True, False or Null response to your query. This model is used where related data needs to be connected together in a database.
The model provides for three responses to any query, made, True, False or Null.
Flat file database This is a model is used to describe encoding methods that present database models as a single file.
In this model, there are no structural relationships between records. A binary file or a plain text file may be used to present a flat file.
The plain text files hold a single record per line. Data may be depicted in different ways, by use of commas to separate the values. Fields are also separated using commas. Using this may at times be time consuming because it takes a lot of time to locate the commas and tab spaces used any time the data is being processed. The flat file is only made of data.
It was the first model for designing a database to be used; it was first implemented by IBM. This model only contains data.
It does not offer any chances for relational models/ concepts. It was used for data storage where strictly only data was being stored. Provided the first database system.
Part 2
Using the table below, choose, describe, and compare five database design models. Your responses for Part 2 should total 1,050 to 1,400 words.
Database Design Model Description Comparison
Flat file database This is a model is used to describe encoding methods that present database models as a single file.
In this model, there are no structural relationships between records. A binary file or a plain text file may be used to present a flat file.
The plain text files hold a single record per line. Data may be depicted in different ways, by use of commas to separate the values. Fields are also separated using commas. Using this may at times be time consuming because it takes a lot of time to locate the commas and tab spaces used any time the data is being processed. The flat file is only made of data.
It was the first model for designing a database to be used; it was first implemented by IBM. This model only contains data.
It does not offer any chances for relational models/ concepts.
It was used for data storage where strictly only data was being stored. Provided the first database system
Network Model This is a data model for data that is naturally modeled to have more than one parent per individual child. This model allows the modeling of multiple related data. It provides for many relationships.
The network model was defined during the Conference on Data Systems Languages, held in 1971. During the conference the model was discussed and approved as a data model.
In the network model, the basic unit is a set. The set is made up of a set name, the owner record type and member record type.
The multi relationships are conceptualized when a member record type has the same role in multiple sets. The main difference of the network model from other models is that there may be one to many and many to many relationships between the records.
It is similar to other data models since it is able to organize data into records and sets.
Used where a flexible relationship between objects needs to be showcased.
Object relational model It is a data model closely related to the relational model however it stands out by implementing object oriented concepts. This involves the use of inheritance and encapsulation among other concepts that are used in the object oriented design. It also entails use of classes and objects. This model supports data types which have been customized together with the use of methods.
This model assimilates characteristics of both relational model and object oriented model.
In this model, data is stored in a database, and using the query language, the data can be changed and stored in a new model. Similar to the relational model, data is stored in a database. The data which is stored in a database can be manipulated using a query language. Similar to object oriented model this model view a database as an object where programs written in object oriented languages are stored.
The model is used to store data in a database, data which is changeable. Used where a model which integrates the relational model concepts with object oriented concepts.
Hierarchical Model The hierarchical model is a model that arranges data in a tree structure. There is one initial source, the parent, which can have many children. It is presented in a structure that resembles a tree. The only relationship that is represented in this data model is the one-to-many relationship. A child has only one parent, but a parent has several children, represented as branches off the parent in a diagram.
The representation of a hierarchical model is similar to a table, where records are equivalent to rows, while attributes are equivalent to columns.
The hierarchical model is the first model to be used by IBM in designing database systems.
Mappings for this model can be represented as 1: N, a representation for one to many. This model was used in creation of databases by IBM before other data models were designed. It is used where flexibility is not needed in the design and implementation of a database system.
Object relational model This is a database management model which mathematically describes how data is structured. This model primarily bases its concepts on the first order predicate logic. It was designed and implemented first by Edgar Codd in 1969.
In this model, tuples is the term that is used to refer to data. Representation of data is in tuples. The data is also grouped into relations.
The main intention of using this model is to have the specifying data and queries declared in the model.
This way, a user can easily search for information in the database, by clearly stating what they require then let the software managing the database handle the process of retrieving the searched data item. This way a user has little input in the process of searching, only feeding a query and leaving the rest to the database management software.
This model is implemented mainly using the standard query language to define data and make searches through the database. In this model, records which are related are connected together using a “key”, unlike in other models.
The model has logic for dealing with searches, known as the three-valued logic, after a search, you either get a True, False or Null response to your query.
This model is used where related data needs to be connected together in a database.
The model provides for three responses to any query, made, True, False or Null.
Using the table below, choose, describe, and compare three database management systems.
Database Management System Description Comparison
Relational Database Management System Also known as a Relational database management system. In this management system, database relationships are treated as a table. This management system consists of three keys, relation, domain and attributes. It contains all fundamental designs sets or records. In this system, sets have one to many mappings and a record contains fields. The data is stored in the computer memory as a two dimensional array, composed of rows and columns. An example is Microsoft SQL Server. This database management system can be used by untrained personnel. Modifications can be made on the entries without changing the entire body. They are much easier to manage.
Column values are a representation of the same thing.
Object orient database management systems This database management system is able to incorporate different data types. Audio and video, graphics and photos can be incorporated using this database management system. This is the most advanced database management system. This database management system can be used to store data which is from different media sources. Data can be stored in a multimedia format. Unlike other database management systems, in this management system, different data types can be stored. Multimedia data items can be stored in this database managing systems.
They are more costly to develop, du e to their complexity.
They can be implemented using special programs called methods.
Hierarchical database management system This database management system manages databases where the relationships among data is hierarchical such that one data item can have only one parent, however, a parent can have more than one child.
Records that are stored consecutively have direct relationships among them. An arrow cannot move backwards it only moves one-way while showing relationships among data. Here, unlike in other database management systems, a child can have only one parent, while a parent can have many children. This is a one to many relationships. This limits the flexibility of the data items in the database.
Answer the following:
What are the similarities and differences between database design models and database management systems?
Similarities between database design models and management systems are that they share similar basic concepts. A database that has been designed using one model can only be managed using a similar management system, for example a database that has been designed using the hierarchical design model can only be implemented using the hierarchical database management system. Similarly a database designed using the object oriented database design model can only be implemented using the object oriented database management system.
A difference between a database management system and a database design model is that the database management is software that is used to implement a database which has already been designed. The database is designed using a database design model. The database design model is used to design a database system while a database management system is used to implement the database.
References
Date, C. J. (1986). An introduction to database sytems (4th ed.). Reading, Mass.: Addison-Wesley.
McFadden, F. R., & Hoffer, J. A. (1991).Database management (3rd ed.). Redwood City, Calif.: Benjamin/Cummings Pub. Co..Rob, P., & Coronel, C. (2002). Database systems: design, implementation, and management (5th ed.). Boston, MA: Course Technology.