Download A database is a collection of data stored in a standard format

A database is a collection of data stored in a standard format designed to be shared by multiple users. Databases are
one of the most important and useful tools available to management and information technology professionals.
They provide the foundation for collecting, organizing, and sharing data across an organization. Virtually, every
area of management uses a database management system (DBMS) – marketing professionals use databases to
analyze sales data, human resource managers to evaluate employees, operations managers to track and improve
quality, accountants to integrate data across the firm, and financial analysts to analyze a company’s performance.
The database management approach provides several significant advantages over traditional programming
techniques. Primary advantages include shorter development times, easier modification, better data integrity and
security, and improved data sharing and integration. However, a DBMS is one of the most complex technology
tools available. Databases have to be carefully designed to gain these advantages. A large-scale DBMS provides
thousands of options and costs hundreds of thousands of dollars. It can take several months to learn all of the
features of a particular DBMS.
A DBMS (Database Management System) is a software that defines a database, stores the data, supports a query
language, produces reports, and creates data entry screens.
Some of the most challenging problems in building applications arise in storing and retrieving data.
Problems include conserving space, retrieving data rapidly, sharing data with multiple users at the same time, and
providing backup and recovery of data. Initially programmers had to solve these problems for every application
they create. Today, the DBMS already provides some of the best solutions to these problems. Making the database
the foundation of an application means that you get all of the powerful features and security without much
additional work.
Databases and Application Development
In the last few years, database systems have become the foundation of almost all application development
projects. From large enterprise relationship systems, to e-business, to stand-alone applications, database systems
store and retrieve data efficiently, provide security, and make it easier to build the applications. Today, when you
build or modify an application, you will first create the database.
Phases in Application Development (Larger projects may require several people in each phase, while smaller
projects might be created entirely by one or two developers.)
1. Feasibility. Define the project and provide estimates of the cost.
2. Analysis. Collect data definitions, forms, and reports from users.
3. Design. Use the collection made in the analysis to design the database and all the new forms, reports, and
user interactions.
4. Development. Create the forms, reports, and application features such as help files.
5. Implementation. Transfer data, install, train, and review.
Steps in Database Design
1. Identify business rules.
2. Define tables and relationships.
3. Create input forms and reports.
4. Combine as application for users.
Business rules and processes are converted into database table and relationship definitions. Forms are defined
that transfer data into the database, and reports use queries to retrieve and display data needed by users. These
forms and reports along with features such as menus and help constitute applications. Users generally see only
the application and not the underlying database or tables.
Components of a Database Management System (The basic feature list is also useful when you have to evaluate
the various products to determine which DBMS your company should use.)
 Database Engine. The heart of DBMS and is responsible for storing, retrieving, and updating the data. This
component is the one that most affects the performance (speed) and the ability to handle large problems
(scalability).
 Data Dictionary. It holds the definitions of all of the data tables and describes the type of data that is being
stored, allows the DBMS to keep track of the data, and helps developers and users to find the data they need.
The data dictionary determines which tables and columns should be used. Most modern database systems hold
the data dictionary as a set of system tables. For example, Microsoft Access keeps a list of al the tables in a
hidden system table called MsysObjects. Oracle includes several system tables that provide information from
the data dictionary.
 Query Processor. A fundamental component of the DBMS that enables developers and users to store and
retrieve data. In some cases the query processor is the only connection you will have with the database.
Queries are derived from business questions. The query language is necessary because natural languages like
English are too vague to trust with a query. To minimize communication problems and to make sure that the
DBMS understands your question, you should use a query language that is more precise than English. The
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DBMS refers to the data dictionary to create a query. When the query is run, the query processor communicates
with the database engine to retrieve the requested data.
Report Writer. A component that enables you to set up the report on the screen to specify how items will be
displayed or calculated. The report writer can be integrated into the DBMS, or it can be a stand-alone
application that the developer uses to generate code to create the needed report. The design template sets the
content and layout of the report. The developer creates a basic report design. This design is generally based on
a query. When the report is executed, the report writer passes the query to the query processor, which
communicates with the database engine to retrieve the desired rows of data. The report writer then formats the
data according to the report template and creates the report complete with page numbers, headings, and footers.
Forms Generator. A component that helps the developer create input forms. It enables developers to build
forms by dragging and dropping items on the screen. A form is used to collect data. It is designed to match the
tasks of the user, making it easy to enter data and loop up information. The query processor is used to obtain
related data and fill in looked-up data in combo boxes.
Application Generator. Consists of tools that assist the developer in creating complete application package.
An application is a collection of forms and reports designed for a specific user task. It is the final package that
you are trying to create.
Communication and Integration. Utilities designed to store and use data in several databases running on
different machines, even if they are in different locations. Modern operating systems and independent
networks, including the Internet, have made it easier to connect databases running in different locations.
Nonetheless, some systems do a better job of using these tools and support connections to share data globally.
Security and Other Utilities. Utilities responsible for establishing and maintaining security access controls
(e.g., identify the user and then provide or limit access to various parts of the database). Security is a complex
issue with databases running on personal computers, because most personal computer operating systems have
few controls. Various administrative utilities are provided by the DBMS. Common features include backup and
recovery, user management, data storage evaluation, and performance-monitoring tools.
Advantages of the Database Management System Approach
1. Minimization or control of data redundancy.
2. Data consistency.
3. Integration of data.
4. Sharing of data.
5. Enforcement of standards.
6. Ease of application development
7. Improved and uniform security, privacy, and integrity.
8. Data independence. The separation of data definition from the program. It enables you to change the data
definition without altering the program and move data to new hardware or a completely different machine.
No need to alter the forms, reports, or programs that use that data. Individual programs can be changed
without having to change the data definition.
Brief History of Database Management Systems
Developers quickly realized that many business applications needed a common set of features for sharing
data, and they began developing database management systems. They gradually refined their goals and improved
their programming techniques. Many of the earlier database approaches still survive, partly because it is difficult to
throw away applications that work. It is worth understanding some of the basic differences between these older
methods.
Hierarchical Databases
The Hierarchical Database approach begins by claiming that business data often exhibits a hierarchical
relationship. This logical database model organizes data in a treelike structure where a record is divided into
segments that that are connected to each other in one-to-many parent-child relationship. It is relatively fast – as long
as you only want to access the data from the top. The most serious problem related to data storage is the difficulty
of searching for items in the bottom or middle of the hierarchy. For example, to find al of the customers who
ordered a specific item, the database would have to inspect each customer, every order, and each item. (Pointer is a
special type of data element attached to a record that shows the absolute or relative address of another record.)
Network Databases
The Network Database has nothing to do with physical networks (e.g., local area networks). Instead, the network
model is named from the network of connections between data elements. This logical database model is a variation
of the hierarchical data model that is useful for depicting many-to-many relationships. Databases can be translated
from hierarchical to network and vice versa in order to optimize processing speed and convenience. The primary
goal of the network model was to solve the hierarchical problem of searching for data from different perspectives.
Although this approach seems to solve the search problems, the cost is high. All arrows must be physically
implemented as indexes or embedded pointers. Essentially, an index duplicates every key data item in the
associated data set and associates the item with a pointer to the storage location of the rest of the data. The problem
with the network approach is that the indexes must be built before the user can ask a question. Consequently, the
developer must anticipate every possible question that users might ask about the data. Worse, building and
maintaining the indexes can require huge amounts of processor time and storage space.
Relational Databases
The Relational Database approach (originated by E.F. Codd in the 1970s) stored data in separate sets of data. The
tables are not physically connected; instead, data is linked between columns. This type of logical database model
treats data as if they were stored in two-dimensional tables. It can relate data stored in one table to data in another
as long as the two tables share a common data element. For example, when retrieving an order, the database can
match and retrieve the corresponding customer data based on CustomerID.
Customer(CustomerId, Name, . . .
Order(OrderID, CustomerID, OrderDate, . . .
ItemsOrdered(OrderID, ItemID, Quantity, . . .
Items(ItemID, Description, Price, . . .
* Tuple. A row or record in a relational database.
* Normalization is the process of creating small stable data structures from complex groups of data when designing
a relational database.
Objected-Oriented Databases
An object-oriented (OO) database is a new and evolving method of organizing. This approach began as a new
method to create programs. This approach to data management stores both data and the procedure acting on the data
as objects that can be automatically retrieved and shared. The goal is to define objects that can be reused in many
programs – thus saving time and reducing errors. The objects can contain multimedia. An object has three major
components: a name, a set of properties or attributes, and a set of methods or functions. The properties describe
the object, just as attributes describe an entity in the relational database. The “methods” are the true innovation of
the OO approach. Methods are short programs that define the actions that each object can take. For example, the
code to add a new customer would be stored with the customer object. The innovation is that these methods are
stored with the object definition.
Hypermedia Databases
The hypermedia database approach to data management transcends some of the limitations of traditional database
methods by organizing data as a network of nodes linked in any pattern established by the user. The nodes can
contain text, graphics, sound, full-motion video, or executable programs.
A feasibility study is a preliminary study undertaken before the real work of a project starts to ascertain the
likelihood of the project's success. It is an analysis of possible alternative solutions to a problem and a
recommendation on the best alternative. It, for example, can decide whether an order processing be carried out by a
new system more efficiently than the previous one. Or, a preliminary study undertaken to assess whether a planned
project is likely to be practical and successful and to estimate its cost. Or, the analysis of the viability of an idea.
A feasibility study could be used to test a new working system, which could be used because:
♦ The current system may no longer suit its purpose,
♦ Technological advancement may have rendered the current system redundant,
♦ The business is expanding, allowing it to cope with extra work load,
♦ Customers are complaining about the speed and quality of work the business provides,
♦ Competitors are not winning a big enough market share due to an effective integration of a computerized system.
Within a feasibility study, six areas must be reviewed, including those of Economics, Technical, Schedule,
Organizational, Cultural, and Legal.
Economic feasibility study
This involves questions such as whether the firm can afford to build the system, whether its benefits should
substantially exceed its costs, and whether the project has higher priority than other projects that might use the same
resources.
Technical feasibility study
This involves questions such as whether the technology needed for the system exists, how difficult it will be to
build, and whether the firm has enough experience using that technology.
Schedule Feasibility study
This involves questions such as how much time is available to build the new system, when it can be built (i.e.
during holidays), interference with normal business operation, etc.
Organizational Feasibility study
This involves questions such as whether the system has enough support to be implemented successfully, whether it
brings an excessive amount of change, and whether the organization is changing too rapidly to absorb it.
Cultural Feasibility study
In this stage, the project's alternatives are evaluated for their impact on the local and general culture. For example,
environmental factors need to be considered.
Legal Feasibility study
Not necessarily last, but all projects must face legal scrutiny. When an organization either has legal council on staff
or on retainer, such reviews are typically standard. However, any project may face legal issues after completion too.
Source(s):http://en.wikipedia.org/wiki/feasibility...
Possible Sources of Ideas for Information Systems
1.
Users
2.
Upper Management
3.
Information System Analysts
4.
Competitors, or firms in other industries
Common Costs and Benefits from Introducing a DBMS (Benefits ca be hard to measure, especially for tactical
and strategic decisions. But it is still important to list potential benefits. Even if you cannot assign a specific value,
managers need to see the complete list)
Costs
Benefits
Up-front/One-time
Cost Savings
Software
Software maintenance
Hardware
Fewer errors
Communications
Less data maintenance
Data conversion
Less user training
Studies and design training
Increased Value
Better access to data
Ongoing Costs
Personnel
Better decisions
Software upgrades
Better communication
Supplies
More timely reports
Support
Faster reaction to change
Software and hardware maintenance
New products and services
Strategic Advantages
Lock out competitors.
Management Requirements for Database Systems
Much more is required for the development of database systems than simply selecting a logical database
model. Indeed, this selection may be among the last decisions. The database is an organizational discipline, a
method, rather than a tool or technology. It requires organizational and conceptual change.
Without management support and understanding, database efforts fail. The critical elements in a database
environment are:
Data Administration. A special organizational function for managing the organization’s data resources, concerned
with information policy, data planning, maintenance of data dictionaries, and data quality standards. The
fundamental principle of data administration is that all data are the property of the organization as a whole. This
requires the formulation of an information policy that specifies its rules for sharing, disseminating, acquiring,
standardizing, classifying, and inventorying information throughout the organization. Information policy lays out
specific procedures and accountabilities, specifying which organizational units share information; where
information can be distributed; and who has responsibility for updating and maintaining the information.
Data Planning and Modeling Methodology. The enterprise-wide planning for data where enterprise analysis is
needed to develop database. This kind of analysis addresses the information requirements of the entire organization
(as opposed to the requirements of individual applications) to identify the key entities, attributes, and relationships
that constitute the organization’s data.
Database Technology and Management. The more technical and operational aspects of managing data, including
physical database design and maintenance. This defines and organizes database structure and content, develops
security procedures to safeguard and the database, develops database documentation, and maintains the database
management software.
Users. The employees who are not computer specialists accessing large databases. It also includes trained computer
specialists.
Levels of Decision Making
 Strategic Decision Making. Determines the long-term objectives, resources, and policies of an organization.
 Management Control. Monitors how efficiently or effectively resources are utilized and how well operational
units are performing.
 Knowledge-level Decision Making. Evaluates new ideas for products, services, ways to communicate new
knowledge, and ways to distribute information throughout the organization.
 Operational Control. Decides how to carry out specific tasks specified by upper and middle management and
establishes criteria for completion and resource allocation.
Types of Decisions (according to Simon (1960))
 Structured (programmed) Decisions. Decisions that are repetitive, routine, and involve a definite procedure for
handling so that they do not have to be treated each time as if they were new.
 Unstructured (non-programmed) Decisions. Decisions in which the decision maker must provide judgment,
evaluation, and insights into the problem definition. These decisions are novel, important, and non-routine, and
there is no well-understood or agreed-upon procedure for making them.
 Semi-structured Decisions. Decisions where only part of the problem has a clear-cut answer provided by an
accepted procedure.
Stages of Decision Making
Making decisions is not a single activity that takes place all at once. The process consists of several
different activities that take place at different times.
 Intelligence. Collecting information to identify the problems occurring in the organization. It indicates why,
where, and with what effects a situation occurs.
 Design. Conceiving of possible alternative solutions to a problem. This may require more intelligence so that
the manager can decide if a particular solution is appropriate.
 Choice. Selecting among the various solution alternatives.
 Implementation. Putting the decision into effect and reporting on the progress of the solution.
Individual Models of Decision Making
 Rational Model. Model of human behavior based on the belief that people, organizations, and nations engage in
basically consistent, value-maximizing calculations or adaptations within certain constraints.
 Bound Rationality and Satisficing. The idea that people will avoid new uncertain alternatives and stick with
tried-and-true rules and procedures. Satisficing is choosing the first available alternative in order to move closer
toward the ultimate goal instead of searching for all alternatives and consequences.
 Muddling Through. The method that involves successive limited comparisons where the test of a good decision
is whether people agree on it.
 Incremental Decision Making. Choosing policies most like the previous policy.
 Psychological Type and Frames of Reference.
i. Cognitive Style describes underlying disposition toward the treatment of information, selection of
alternatives, and evaluation of consequences.
1. Systematic Decision Makers. Cognitive Style that describes people who approach a problem by
structuring it in terms of some formal method.
2. Intuitive Decision Makers. Cognitive style that describes people who approach a problem with multiple
methods in an unstructured manner, using trial and error to find a solution.
Organization Models of Decision Making. Models of decision making that take into account the structural and
political characteristics of an organization.
 BureaucraticModels. Models where decisions are shaped by the organization’s standard operating procedures
(SOPs)
 Political Models. Models where decisions result from competition and bargaining among the organization’s
interest groups and key leaders.
 “Garbage Can” Model. A model that states organizations are not rational and decisions are solutions that
become attached to problems for accidental reasons.
Database Design and the Unified Modeling Language
For several years, entity-relationship (ER) diagrams were the predominant modeling technique for database
design. However, this approach causes problems for instructors (and students) because there are several different
diagramming techniques. An entity-relationship diagram is a methodology for documenting databases illustrating
the relationship between various entities in the database.
Unified modeling language (UML) class diagrams, although very similar to ER diagrams, are superior in
several ways. They: are standardized, so students (and instructors) need learn only one set of notations; are
“cleaner” in the sense that they are easier to read without bubbles and cryptic notations of traditional ER diagrams;
provide an introduction to object-oriented design, so students will be better prepared to move into future jobs; and
prepare students to move into future jobs with their rapid adoption.
The basic similarities between ER and class diagrams are (1) entities (classes) are drawn as boxes, (2)
binary relationships (associations) are drawn as connecting lines, and (3) n-ary associations (relationships) are
drawn as diamonds. Hence, the overall structure are similar. The main difference between UML and ER diagrams
occur in the details. In UML the multiplicity of an association is shown as simple numerical notation instead of
cryptic icon.
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Extracted from Database Management Systems International 3 rd Edition ©2005 by Gerald V. Post