WAP -WIRELESS APPLICATION PROTOCOL

The WAP Forum

In 1997, Ericsson, Motorola, Nokia, and Unwired Planet formed the WAP Forum(www.wapforum.org). More than 90 companies in the wireless telecommunications business are members of the WAP Forum. WAP is the standard developed by the WAP Forum, a consortium formed by device manufacturers, service providers, content providers, and  application providers. WAP specifies an application framework and protocols for wireless devices. WAP is a kind of fusion of mobile networking technologies and Internet technologies.

The WAP Forum’s objectives include :

·         To bring Internet content and advanced data services to digital cellular phones and  other wireless terminals.

·          To create an interoperable wireless protocol specification that will work across  differing wireless network technologies.

·          To enable the creation of content and applications that could scale across a wide range of wireless bearer networks and device types.

·         To embrace and extend existing standards and technologies

The key features provided by WAP include :

·         A programming model similar to the Internet

·         Wireless Markup Language(WML)

·         WML Script

·         Wireless Telephony Application(WTA)

·         Optimized protocol stack

The WAP architecture provides a scalable and extensible environment for application  development on mobile communication devices. It achieves this through a layered protocol design, covering protocols at Layer 4 and above. The WAP protocol stack is independent of the underlying network, which could take the form of GSM, CDMA, CDPD, iDEN, etc. Hence, WAP is essentially an application stack specification; it is not network-centric.

Wireless Application Environment(WAE)

Generally, WAE enables a spectrum of applications to be supported over WAP. WAE has two main elements, namely: (a) user agents, and (b) services and formats. The former includes the WML and WTA(Wireless Telephone Application) user agents. The latter consists of WML scripts, image formats, etc. A user agent can take the form of a Web browser. The WML user  agent is responsible for the interpretation of WML and WMLScript. WAP employs the same addressing model as in the Internet, that is, it use Uniformed Resource Locators(URLs). AURL uniquely identifies an available resource. WAP also uses Uniform Resource Identifiers (URIs) to address resources that are not accessed via well-known protocols.

Wireless Session Protocol(WSP)

The WSP provides both connection-oriented and connectionless services. It is optimized for low-bandwidth networks with relatively long latency. WSP is a binary version of HTTP version  1.1, but with the additions of : (a) session migrations, (b) header caching, etc. WAP connection mode allows the establishment of sessions between a client and the WAP gateway or proxy. It  can handle session interruptions as a result of mobility and reestablish session states at a later point in time. Header caching allows better bearer utilization since in HTTP, most of the  requests contain static headers that need to be re-sent again.

Wireless Transaction Protocol(WTP)

WTP is designed for transaction-style communications on wireless devices. In a transaction, users express their intentions and financial commitments to service providers for processing Very often, such transactions demand reliable, fast, and secure communications. WTP is a  lightweight protocol suitable for implementation in thin clients. WTP implements selective  retransmission of lost segments.

Wireless Transport Layer Security(WTLS)

WTLS is needed for WAP to ensure data integrity, privacy, authentication, and protection from denial-of-service. It is based on Transport Layer Security(TLS) 1.0, but optimized for  wireless channels. It provides transport layer security between a WAP client and the WAP gateway/proxy. Digital certificates are used for authentication and non repudiation of server and client. Encryption is also used to enhance the degree of confidentiality.

Wireless Datagram Protocol(WDP)

WDP is the transport layer protocol in WAP. It has the same functionality provided by the  Internet User Datagram Protocol(UDP). Whether WAP uses UDP or WDP, datagram delivery  services are provided by port number functionality and the characteristics of different beare services are hidden from the upper layers. WDP can be extended to provide segmentation and

reassembly functions

 DBMS

a. Data:

·         It is a collection of information.

·         The facts that can be recorded and which have implicit meaning known as 'data'.

·         Example:

                 Customer  ----- 1.cname.

                                               2.cno.

                                               3.ccity.

b. Database:

·         It is a collection of interrelated data.

·         These can be stored in the form of tables.

·         A database can be of any size and varying complexity.

·         A database may be generated and manipulated manually or it may be computerized.

·         Example:

 Customer database consists the fields as cname, cno, and ccity

Cname	Cno	Ccity

c. Database System:

1.What are the advantages of a database system over conventional file processing systems? (8 Marks, April-2000)

·         It is computerized system, whose overall purpose is to maintain the information and to make that the information is available on demand.

·         Advantages:

                  1.Redundency can be reduced.

                  2.Inconsistency can be avoided.

                  3.Data can be shared.

                  4.Standards can be enforced.

                  5.Security restrictions can be applied.

                  6.Integrity can be maintained.

                  7.Data gathering can be possible.

                  8.Requirements can be balanced.

d. Database Management System (DBMS):

1.What are the advantages of DBMS over File processing systems?

                       

File Processing System:

·         It is a collection of interrelated data and programs to access the data.

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

·         It is a 'General Purpose Software System’ that facilitates the processes of Defining, Constructing and Manipulating databases for various applications.

·         Advantages:

1.Data Independence.

2.Efficient Data Access.

3.Data Integrity and security.

4.Data administration.

5.Concurrent access and Crash recovery.

6.Reduced Application Development Time.

·         Dis-advantages:

1.Data Redundancy.

2.Data Inconsistency.

3.Difficulty in accessing the data.

4.Data Isolation.

5.Security Problems.

LEVELS OF DATA ABSTRACTION 

 This is also called as 'The Three-Schema Architecture’, which can be used to separate the user applications and the physical database.

1.Physical Level:

·         This is a lowest level, which describes how the data is actually stores.

·         Example:

                        Customer account database can be described.

2.Logical Level:

·         This is next higher level that describes what data and what relationships in the database.

·         Example:     

               Each record

                       type customer = record

                                   cust_name: sting;

                                         cust_city: string;

                                         cust_street: string;

                              end;

3.Conceptual (view) Level:

·         This is a lowest level, which describes entire database.

·         Example:

                        All application programs.

                       

DATA MODELS

·         The entire structure of a database can be described using a data model.

·         A data model is a collection of conceptual tools for describing

·         Data models can be classified into following types.

1.Object Based Logical Models.

2.Record Based Logical Models.

3.Physical Models.

Explanation is as below.

1.Object Based Logical Models:

·         These models can be used in describing the data at the logical and view levels.

·         These models are having flexible structuring capabilities classified into following types.

a.       The entity-relationship model.

b.      The object-oriented model.

c.       The semantic data model.

d.      The functional data model.

2.Record Based Logical Models:

·                     These models can also be used in describing the data at the logical and view levels.

·                     These models can be used for both to specify the overall logical structure of the database and a higher-level description.

·                     These models can be classified into,

1.   Relational model.

2.   Network model.

3.      Hierarchal model.

3. Physical Models:

·         These models can be used in describing the data at the lowest level, i.e. physical level.

·         These models can be classified into

a.       Unifying model

b.      Frame memory model

.

5.Entity Relational Model (E-R Model)

                     The E-R model can be used to describe the data involved in a real world enterprise in terms of objects and their relationships.

Uses:

·                     These models can be used in database design.

·                     It provides useful concepts that allow us to move from an informal  

               description to precise description.

·                     This model was developed to facilitate database design by allowing the specification of overall logical structure of a database.

·                     It is extremely useful in mapping the meanings and interactions of real world enterprises onto a conceptual schema.

·                     These models can be used for the conceptual design of database

                  applications.

RDBMS=== LECTURE CLASS I

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1. What is DBMS? Explain its features.

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A. In a typical file processing system, permanent records are stored in various files. A

number of different application programs are written to extract records from and add recordsto the appropriate files. But this method has a number of disadvantages, such as DataRedundancy, Difficulty in access, Data Isolation, Concurrent Access, Security Problems, andIntegrity Problems..

A Database Management System (DBMS) consists of a collection of interrelated data and a set of programs to access this data. This collection of Data is called Database. The Primary goal of a DBMS is to provide a convenient environment to retrieve and store database information.

Features of DBMS:-

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1.

The integration and sharing of data files minimizes the duplication and redundancy of

data to a great extent.

2.

Integration of data files also results in a considerable saving of storage space and in

data entry and data storage costs.

3.

Fewer application programs need to be developed for obtaining various reports due to independence of programs and data.

4.

The query language facility helps non-programming persons to access the database

for information as needed without the help of any programmer.

5.

Faster preparation of information to support non-recurring tasks and changing

conditions is possible.

6.

Updation of data becomes easier due to integration of data file. Fewer errors may

when several records may be updated simultaneously.

7.

Large database maintenance.