Day 2 - CS6302 - Unit I - Database System Terminologies , Database characteristics.ppt

•

_{Database System Terminologies}

– _{Database Properties} – _{Basic Definitions}

– _{An Example}

•

_{A database has the following implicit properties:}

– _{A database represents some aspect of the real world,}

sometimes called the miniworld or the universe of discourse (UoD). Changes to the miniworld are

reflected in the database.

– _{A database is a logically coherent collection of data}

with some inherent meaning. A random assortment of data cannot correctly be referred to as a database.

– _{A database is designed, built, and populated with}

Basic Definitions

• Database:

– A collection of related data.

• Data:

– Known facts that can be recorded and have an implicit meaning.

• Mini-world:

– Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university.

• Database Management System (DBMS):

– is a collection of programs that enables users to create and maintain a database.

•

_meta-data

– _{The database definition or descriptive information is}

also stored by the DBMS in the form of a database catalog or dictionary; it is called meta-data

•

_{Data manipulaton}

– _{Manipulating a database includes functions such}

as querying the database to retrieve specific data, updating the database to reflect changes in the miniworld, and generating reports from the data.

•

_{Data sharing}

– _{Sharing a database allows multiple users and}

•

_An

_{application program}

– _{accesses the database by sending queries or}

requests for data to the DBMS.

•

_Query

– _{typically causes some data to be retrieved;}

•

_Transaction

– _{may cause some data to be read and some data to}

be written into the database.

•

_Protection

•

_maintenance:

– _{the DBMS must be able to maintain the database}

• An Example Database (University Database)

• _{STUDENT record includes data to represent the student’s Name,}

Student_number, Class (1 for freshman, 2 for sophomore, 3 for junior, 4 for senior, and 5 for graduate student.), and Major (such as mathematics or ‘MATH’ and computer science or ‘CS’)

– COURSE record includes data to represent the Course_name,

– the SECTION file stores data on each section of a course

– the GRADE_REPORT file stores the grades that students receive in the various sections they have completed

Typical DBMS Functionality

• _{Define a particular database in terms of its data types,}

structures, and constraints

• _{Construct or Load the initial database contents on a secondary}

storage medium

• _{Manipulating the database:}

– _{Retrieval: Querying, generating reports}

– _{Modification: Insertions, deletions and updates to its content} – Accessing the database through Web applications

• _{Processing and Sharing by a set of concurrent users and}

Example of a Database

(with a Conceptual Data Model)

– _{SECTIONs are of specific COURSEs} – _{STUDENTs take SECTIONs}

– _{COURSEs have prerequisite COURSEs} – _{INSTRUCTORs teach SECTIONs}

Main Characteristics of the Database

Approach

• _{Self-describing nature of a database system:}

– _{A DBMS catalog stores the description of a particular database}

(e.g. data structures and types)

– _{The description is called meta-data.}

– _{This allows the DBMS software to work with different database}

•

_{Insulation between programs and data:}

– _{Allows changing data structures and storage organization without having to}

change the DBMS access programs.

•

_{Data Abstraction:}

– A data model is used to hide storage details and present the users with a conceptual view of the database.

– _{Programs refer to the data model constructs rather than data storage details}

•

_{Support of multiple views of the data:}

•

_{Sharing of data and multi-user transaction}

processing:

– _{Allowing a set of concurrent users to retrieve from}

and to update the database

– _{Care is needed to avoid interferences}

– _{Concurrency control within the DBMS guarantees}

that each transaction is correctly executed or aborted

– _{Recovery subsystem ensures each completed}

transaction has its effect permanently recorded in the database

Database Users

•

_{Users may be divided into}

– _{Those who actually use and control the database}

content, and those who design, develop and

maintain database applications (called “Actors on the Scene”), and

– _{Those who design and develop the DBMS software}

Database Users

•

_{Actors on the scene}

– _{Database Designers:}

• _{Responsible to define the content, the structure, the}

constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs.

– _{Database administrators:}

• _{Responsible for authorizing access to the database, for}

Categories of End-users

•

_{Actors on the scene (continued)}

– _{End-users: They use the data for queries, reports}

and some of them update the database content. End-users can be categorized into:

• Casual: access database occasionally when needed

• _{Naïve or Parametric: they make up a large section of}

the end-user population.

– They use previously well-defined functions against the database.

Categories of End-users (continued)

• Sophisticated:

– These include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities.

– Many use tools in the form of software packages that work closely with the stored database.

• _Stand-alone:

– Mostly maintain personal databases using ready-to-use packaged applications.

– An example is a scientists that creates a database for its own experiments.

– Another example is a user that maintains an address book

Advantages of Using the Database

Approach

•

_{Interacting easily with data using high-level}

dedicated tools

•

_{Controlling redundancy in data storage and in}

development and maintenance efforts.

– _{Ensuring consistency of data.}

•

_{Restricting unauthorized access to data.}

•

_{Providing storage structures (e.g. indexes) for}

Advantages of Using the Database

Approach (continued)

•

_{Providing backup and recovery services.}

•

_{Providing multiple interfaces to different}

classes of users.

•

_{Representing complex relationships among}

data.

•

_{Enforcing integrity constraints on the}

Additional Implications of Using the

Database Approach

•

_{Potential for enforcing standards:}

– _{This is very crucial for the success of database}

applications in large organizations. Standards refer to data item names, display formats, screens,

report structures, Web page layouts, etc.

•

_{Reduced application development time:}

– _{Applications can exploit the high-level database}

primitives.

– _{Incremental time to add each new application is}

Additional Implications of Using the

Database Approach (continued)

•

_{Flexibility to change data structures:}

– Database structure may evolve as new requirements

are defined.

•

_{Availability of current information:}

– _{Extremely important for on-line transaction systems}

such as airline, hotel, car reservations.

•

_{Economies of scale:}

– _{Wasteful overlap of resources and personnel can be}

Historical Development of Database

Technology

• Early Database Applications:

– The Hierarchical and Network Models were introduced in mid 1960s and dominated during the seventies.

– _{A bulk of the worldwide database processing still occurs using}

these models, particularly, the hierarchical model.

• _{Relational Model based Systems:}

– Relational model was originally introduced in 1970, was heavily researched and experimented within IBM Research and several universities.

– Relational DBMS Products emerged in the early 1980s.

– _{Most of the systems used today are based on it (Microsoft}

Historical Development of Database

Technology (continued)

• _{Object-oriented and emerging applications:}

– _{Object-Oriented Database Management Systems (OODBMSs)}

were introduced in late 1980s and early 1990s to cater to the need of complex data processing in CAD and other applications.

• Their use has not taken off much.

– _{Many relational DBMSs have incorporated object database}

concepts, leading to a new category called object-relational DBMSs (ORDBMSs)

– _{Extended relational systems add further capabilities (e.g. for}

Historical Development of Database

Technology (continued)

•

_{Data on the Web and E-commerce}

Applications:

– _{Web contains data in HTML (Hypertext markup}

language) with links among pages.

– _{This has given rise to a new set of applications and}

E-commerce is using new standards like XML (eXtended Markup Language).

– _{Script programming languages such as PHP and}

JavaScript allow generation of dynamic Web pages that are partially generated from a database.

Extending Database Capabilities

• New functionality is being added to DBMSs in the following areas:

– Scientific Applications

– XML (eXtensible Markup Language)

– Image Storage and Management

– Audio and Video Data Management

– Data Warehousing and Data Mining

– Spatial Data Management

– Time Series and Historical Data Management

When not to use a DBMS

• _{Main inhibitors (costs) of using a DBMS:}

– _{High initial investment and possible need for additional}

hardware.

– _{Overhead for providing generality, security, concurrency control,}

recovery, and integrity functions.

• _{When a DBMS may be unnecessary:}

– _{If the database and applications are simple, well defined, and}

not expected to change.

– _{If there are stringent real-time requirements that may not be}

met because of DBMS overhead.

When not to use a DBMS

•

_{When no DBMS may suffice:}

– _{If the database system is not able to handle the}

complexity of data because of modeling limitations

– _{If the database users need special operations not}

Types of Databases and Database

Applications

•

_{Traditional Applications:}

– _{Numeric and Textual Databases}

•

_{More Recent Applications:}

– _{Multimedia Databases}

– _{Geographic Information Systems (GIS)} – _{Data Warehouses}

– _{Real-time and Active Databases} – _{Many other applications}

•

_{We will focus on traditional applications, with}

Summary

•

_{Types of Databases and Database Applications}

•

_{Basic Definitions}

•

_{Typical DBMS Functionality}

•

_{Example of a Database (UNIVERSITY)}

•

_{Main Characteristics of the Database Approach}

•

_{Database Users}