For learning web services we should know the following things.

4) web  services
5) security


SOAP  is  an  XML  based  protocol  for  exchanging  information  between  computers. Soap is an XML. That is soap application of the XML specification.

SOAP    messaging

For  exchanging  information  between  computers  SOAP  is  an XML  based  protocol.
Features of SOAP
1) SOAP is a communication protocol
2) SOAP is for communication between applications
3) SOAP is a format for sending messages
4) SOAP is designed to communicate via Internet
5) SOAP is platform independent
6) SOAP is language independent
7) SOAP is simple and extensible
8) SOAP allows you to get around firewalls
9) SOAP will be developed as a W3C standard
10) SOAP is acronym for Simple Object Access Protocol
11) SOAP can extend HTTP for XML messaging
12) SOAP provides data transport for Web services

SOAP is the XML way of defining what information gets sent and how SOAP   is used for a variety of   messaging   systems. It is delivered in a variety   of transport protocols. SOAP    is easily   connected to remote   services.  It invokes remote methods.  SOAP    messages are written entirely in    XML. Therefore it is uniquely platform and language in depended.
Soap recommended knowledge
                              Before  you  proceed  further  you  should  be  familiar  with  XML   and  XML  namespace.  As  background  for  their  principles, a  quick  overview  of  some  common  web  services  terms  will  be  helpful.  It is  useful  to  have  a  cursory  view  of  existing  management  platforms.  A    SOAP interface is a set of operations. This article uses the terms    SOAP interface and WSDL interchangeably. WSDL  bears  many  similarities  to  the interface  definition  language  in  CORBA, COMT  and  distributed  computing  environment styles  of  computing. That is the WSDL document itself written in XML.  The other important flavor   of     SOAP   is the document exchange form.

READ  Developing web services -part 1

2.  WSDL definitions and their relationship to code

WSDL Usage
                                  It  is used  in combination  with    SOAP   Web  service   can  read  the WSDL  to  determine  what  functions  are available  on  the  server.  Data  types  used  are  embedded  in  the  WSDL  file   in  the  form  of   XML  scheme.  The  client  use  SOA  to  call  one  of  the  functions  listed  in  the  WSDL.
1) WSDL   is an XML based language.
2) WSDL stands for Web Services Description Language.
3) WSDL is an XML based protocol for information exchange in decentralized and distributed environments.
4) WSDL is the standard format for describing a web service.
5) WSDL definition describes how to access a web service and what operations it will perform.
6) WSDL is a language for describing how to interface with XML-based services.
7) WSDL is an integral part of UDDI, an XML-based worldwide business registry.
8) WSDL is the language that UDDI uses.
9) WSDL was developed jointly by Microsoft and IBM.
10) WSDL is pronounced as ‘wiz-dull’ and spelled out as ‘W-S-D-L’
11) WSDL Abstract:

3.  Publishing services to a   UDDI directory

                UDDI   stands for universal description, discovery   and   integration.  It  aims  to  enable   business  to  quickly ,easily  and  dynamically   find  and  carry  out  transactions  with  one  another. UDDI creates   a global, platform – independent, open   architecture   space that will benefit businesses.The UDDI registry   can be divided into two   categories.  They   are

    1.                UDDI and web services
    2.                UDDI and business registry

1. UDDI   and web   services

      The owners   of web   services     publish   them to the UDDI registry.  The   UDDI   registry   maintains   pointers   to the   web   service   description   and to the service.  The   UDDI   allows clients to search    this registry   find the intended   service   and retrieve its   details.  These details   include   the   service   innovation. Through   a programming    interface   web   services capabilities   are exposed.  A typical client inquiry consists   of two objects.  They   are
1) To find an implementation   of a known   interface.
2) To  find  the   updated   value  of   the  inn vocation  point [ that  is ,  access  point]  of a  known  binding   template  ID.

READ  What is Web Service

2. UDDI  and   business  registry

       UDDI  enables  companies   to  advertise   the  business  products and  services  they  provide, as  well  as  how  they  conduct  business    transactions  on  the  web.  The  minimum  required   information  to  publish  a  business   is  a   single  business  name  .
A    business   registry   includes the following things.
a) Business    identification
b) Service  Description
c) Standards  compliance
Custom   categories

Exposing   legacy  applications  as  web  services
      Some   of the definitions   are given below and all the definitions   are   correct
1. A web service is available   over the internet.  It  uses  a  standardized  XML  messaging  system.XML  is  used  to  encode  all  communications to  a  web  service. Web  services  are  self  contained Categories
2. Modular, distributed dynamic applications that can   be described, published, located.  These applications can be local, distributed or web based.  Web services are built on top of   open standards.
E.g.:- TCP/IP, HTTP, Java, HTML and XML.

3. Web   services are XML   based information.  It uses the internet for direct application to application interaction. These systems include program, objects, messages or documents.

4. A web service is a collection of open protocols. It is used for exchanging data between applications or systems.
Some  services  that  are  used  for  summarizing a web  service  is  given  below.
• Is available over the Internet or private (intranet) networks
• Uses a standardized XML messaging system
• Is not tied to any one operating system or programming language
• Is self-describing via a common XML grammar
• Is discoverable via a simple find mechanism

READ  Web Services Tutorial - Setting up environment

  Components of Web Services

 Some   of the    components of web services are given below.

• SOAP (Simple Object Access Protocol)
• UDDI (Universal Description, Discovery and Integration)
• WSDL (Web Services Description Language)

5. Advanced  topics  such  as  security

         Security is critical to web services. There are 3 specific security issues with web services.
1. Confidentiality
2. Authentication
3. Network   security

1. Confidentality
   A client sends an XML request to a server. The question is that the communication remains confidential.  Answer lies here.
• XML-RPC and SOAP run primary on top of HTTP.
• HTTP has support for Secure Sockets Layer (SSL).
• Communication can be encrypted via the SSL.
• SSL is a proven technology and widely deployed.
        A single web service may consist   of a chain of applications.

2. Authentication
      The  following  options  can  be  considered   for  some  of  the    questions  but  there  is no  clear consensus  on  a strong  authentication Scheme.
1. HTTP   includes built in support for basic and digest authentication.
2. SOAP   security extentions; Digital signature leverages is the public key cryptography to digitally sign SOAP   messages. This  enables  the client  or  server  to  validate  the  identity  of  the  other  party.
3. The OASIS is   working on the SAML.
3. Network Security
        It   has been the subject of much debate. One possibility to filter out all   HTTP post requests   that set their content   type   to   text/XML. Another  alternative  is  to  filter  for  the  SOAP  action  HTTP  header  attribute. Firewall vendors are also   currently   developing   tools   designed to filter web service   traffic.