SOA VS DISTRIBUTED INTERNET ARCHITECTURE

distributed architecture consists of many components but it reduces problem of centralization on server.It provides a dedicated servers which shares and manages database connections.distributed architecture introduces a new physical tier web server,which replaced HTTP by RPC protocol to communicate between remote web and application server

Application Logic:
 SOA is similar to distributed architecture provider logic lies in server side but diffierence lies in principles.
components  are tight coupled and processing is wasted to locate component at runtime whereas web services  are loosely coupled thus it introduces oppurtunity for reuse and extensibility.

Application Processing:
 Distributed architecture promotes proprietary protocols like DCOM and CORBA for remote data exchange.It supports creation of stateful and stateless components.
  SOA relies on message based communication,it involves serialization and deserialization of SOAP messages
containing XML document payloads

Technology:
  Distributed computing consists of components,server side scripts and web technologies like HTML and HTTP.SOA consists of distributed objects using Xml and web services.

Security:
  Traditional security architectures includes approaches like delegation and impersonation,encryption to HTTP protocol.SOA rely heavily extension and concepts provided by WS-Security framework,SOA emphasize on security logic.SOAP messages provides header in security logic can be stored.

Administration:
 Distributed  architecture introduces web server and physical environment using HTTP.SOA requires additional runtime administration.problems with messaging  framework can go undetected than with RPC based data exchange.

SOA VS HYBRID WEB SERVICE ARCHITECTURE

Web services as component wrappers:
   The primary role of web service is to introduce integration layer consists of wrapper service that enable synchronous communication via SOAP messages and enable features offered by third party utility web services.SOA provides support for messaging model and specific  design requirements provided by SOA principles, loose coupling,point-to-point communication.

Web Services Within SOA:
   SOA can vary in size and quality.SOA are built with web services designed to automate one or more business process it promotes organization of services into specialized layers that abstract specific part of enterprise logic.it provides interoperability for proprietary application platform that evolves business automation process

Comparision of SOA with Past Architectures

SOA Vs Client-Server architecture:-
   
Application Logic    
client-server places its majority of logic in client software which controls user experience and backend resources
whereas in SOA any software capable of exchanging SOAP messages are service requestors,it partitions logic into autonomus units to provide resuability across applications.

Application Processing
               Since logic resides in client side it must process bulk data,it must establish its own database connections which are expensive.client side executables are fully statefull and consumes a steady amount of PC memory whereas in SOA      processing is distributed and consists of explicit boundaries and resourse requirements to deploy services

Technology:-
  Client-Server uses technology like visual studio,C++ and database like mysql,sybase and RDBMS whereas SOA expands by adding web technologies like HTML,CSS,HTTP along with XML and SOAP messages.

Security:-
       Client-server is centralized at server level security.it can also control client executables and operating systems and data is protected via single point of authentication whereas in SOA security is provided by WS
security framework.

Principles Of SOA

The Principles of SOA are:

1.Reduced Cost :-
        SOA enables extensive reuse of existing funtionality  and infrastructure in multiple integrated projects.

2.Increased Flexibility :-
        SOA quickly adapt to applications inorder to meet changing business requirements and new         technologies  over time.

3.Integrates Incrementally :-
       This is the key benefit of SOA. It enables the users to provide knowledge based solutions which can be   integrated later in incremental fashion.

4.Loosely Coupled :-
           SOA proponents are loosely coupled. It depends on dimensionality like
Time:-when time is loosely coupled there is no need to be up and running at same time to communicate.
Location :-when location is loosely coupled participants can change location without having to re-program,reconfigure or restart communication among partners
Interface:- it provides a generic interface to communicate among partners.

5.Vendor Independent :-
           SOA does not depends upon particular vendor products whether it is commercial or free and open source.This implies interoperability and portability for applications.

6.Service Composability :-
service composability can be broken up in to two basic principles: service discoverability and service composition.Service discoverability is meant to help one avoid the accidental creation of services that are either redundant or implement logic that is redundant.





   






 

car.dtd

<?xml version = "1.0" encoding = "utf-8"?>
<!ELEMENT cars(ad+)>
<!ELEMENT ad(make,model,year,color,engine,number_of_doors,transmission_type,accessories)>
<!ELEMENT make(#PCDATA)>
<!ELEMENT model(#PCDATA)>
<!ELEMENT year(#PCDATA)>
<!ELEMENT color(#PCDATA)>
<!ELEMENT engine(#PCDATA)>
<!ELEMENT number_of_doors(#PCDATA)>
<!ELEMENT transmission_type(#PCDATA)>
<!ELEMENT accessories(#PCDATA)>

<!ATTLIST accessories radio CDATA #REQUIRED>
<!ATTLIST accessories air_conditioner CDATA #REQUIRED>
<!ATTLIST accessories power_window CDATA #IMPLIED>
<!ATTLIST accessories power_steering CDATA #IMPLIED>
<!ATTLIST accessories power_brake CDATA #IMPLIED>

Ex 7.1 xml document

<?xml version = "1.0" encoding = "Utf-8"?>
<!DOCTYPE cars SYSTEM "cars.dtd">
<cars>
 <ad>
   <make>Toyoto</make>
   <model>Corolla</model>
   <year>2000</year>
   <color>black</color>
   <engine>
        <number_of_cylinders>2</number_of_cylinders>
        <fuel_system>4 stroke petrol</fuel_system>
   </engine>
   <number_of_doors>4</number_of_doors>
   <transmission_type>continously variable</transmission_type>
  
   <accessories radio = "yes"
                air_conditioner = "yes"
                power_window = "no"
                power_steering = "no"
                power_brake = "no">accessories </accessories>
 </ad>

 <ad>
   <make>Cheverlet</make>
   <model>Tavera</model>
   <year>2000</year>
   <color>red</color>
   <engine>
        <number_of_cylinders>4</number_of_cylinders>
        <fuel_system>4 stroke diesel</fuel_system>
   </engine>
   <number_of_doors>4</number_of_doors>
   <transmission_type>dual clutch</transmission_type>
  
   <accessories radio = "yes"
                air_conditioner = "yes"
                power_window = "yes"
                power_steering = "no"
                power_brake = "no">accessories</accessories>
 </ad>
</cars>

Evolution of SOA

Earlier programmers find it difficult to write more complex programs so they required a better way to reuse the code than rewriting so they opted modular design but they needed higher level of abstraction so object oriented design was evolved. Component-based software was a good solution for reuse and maintenance, but it doesn't address all of the complexities  faced by developers.

SOA  provides a solution to all of the above by eliminating the problems of protocol, platforms and integrated applications.

The key components of SOA are:

Services
Messages
Dynamic discovery
Web services


 SOA, in combination with web services reduces complexity. Application integration is one of the major issues companies face today SOA can solve  System availability, reliability, and scalability. 

Mashup

A mashup  is a Web application that combines multiple services into a single application.

The main characteristics of the mashup are combination, visualization, and aggregation. Mashup makes existing data more useful for personal and professional use.

The first mashup application was  used to map services or photo services to combine these services with data of any kind.
There are many types of mashup such as
  Data mashups
  Consumer mashups
  Enterprise mashups.               


 Data mashups combine similar types of media and information from multiple sources into a single representation.

Consumer mashups combines different data types such as visual elements and data from multiple sources .

Business mashups  applications  combines their own resources, application and data, with other external Web Services.
The architecture of a mashup is divided into three layers:

• Presentation: It defines user interface by adopting technologies like HTML,CSS Javascript and AJAX.

• Web Services: The functionality can be accessed using the API services and technologies like RPC, SOAP,REST.

• Data: Handling of data like sending, storing and receiving are  performed using technologies like XML and JSON.

Web Services Vs Web Application

Web Services provides a means to communicate between electronic devices.It interacts with other systems using SOAP protocol.data is conveyed using HTTP with XML.

      Web Application is an application that is accessed over internet.Web Application are popular due its user friendly appearance of browser to clients.Some of common application are webmail,retail sales and online auction.                       


Web API is a development in Web services  where emphasis has been moving away from SOAP based services towards  REST based communications.Web API is typically a defined set of Hypertext Transfer Protocol (HTTP) request messages along with a definition of the structure of response messages, usually expressed in an Extensible Markup Language (XML) or JavaScript Object Notation (JSON) format.

Web applications commonly use a combination of server-side script  and client-side script  to develop the application. The client-side script deals with the presentation of the information while the server-side script deals with  storing and retrieving the information.

    

The main components of web services are:
XML(Extensible Markup Language)
                  XML is a simple,text based,self descriptive markup language.It is used to describe logical structures of data in different ways.It helps in data exchange using DTD or XML schema.

SOAP(Simple Object Access Protocol)                    
                  SOAP is a simple but powerful protocol designed for data exchange in an interoperable and extensible form.  

WSDL(Web Service Description Language)
                  WSDL is an Xml file,which describe services.It provides information about the services,names,service location.

 UDDI(Universal Description,Discovery and Integration)
                   It is a specification that is designed to manage business and services-related information UDDI is a registry service that helps to realize service discovery and service invocation.

Web Services

Web services are services deployed on internet.Web services use standard network and application interfaces and protocols.Web services expose their capabilities to client application not their implementation which makes it platform independent and makes it compatible with client applications.

Web services cut down cost by focusing on value added contributions and uses third party applications.It reduces errors from complex large monolithic application and also reduces time-to-market. The technology that form the foundation of web services are SOAP,WSDL and UDDI.
 
web services uses XML based language like WSDL to describe services.WSDL  is a client application that determines location of remote web services and describes how to access and use each functions.

The protocols were developed to leverge XML and information exchange. Web Services uses SOAP protocol which  uses XML-based mechanism for information exchange between application within a distributed environment.