Web Services in Cloud Computing

Cloud computing web services are one of the integral parts of the modern Internet. They assist in getting in touch through various applications or systems with one another for the interchange of data and sharing functionalities with the help of the Internet medium. With the advent of technologies in cloud computing, web services started finding wide applications in interconnecting different technologies and platforms to facilitate communication and collaboration with various systems. An introduction to the importance and the role of web services regarding cloud computing is illustrated below.

What are web Services in Cloud Computing

Cloud Computing Web Services involve integrating web-based applications that are implemented to allow open standards over an Internet Protocol backbone. It enables two electronic devices to communicate over a network. The means are provided through different standards that include HTTP, XML, SOAP, and WSDL, through which various applications can communicate with each other. This makes the data and service provision across different systems and platforms inter-operable and cooperative in the cloud.

Components of Web Services

• XML (Extensible Markup Language): XML can be described as a document tagging language designed to use tag-based encoding when facilitating the creation of structured documents. This is used in forming the format of structuring information being exchanged between web services.
• SOAP (Simple Object Access Protocol): This is a communication platform that has no relation to the transportation protocol. This is a specification for a framework, but SOAP is a messaging protocol based on XML, and it is intended to be used together with other protocols and technologies for building such a framework. The most beautiful thing about web services and SOAP is that everything goes through HTTP, the standard web protocol.
• WSDL (Web Services Description Language): A Web service cannot be used if it can't be found. The implementing client has to know where the web service is located. Also, to invoke the correct web service, the client application has to understand what the web service does. This is done with the help of Web services description language(WSDL). The WSDL file is another XML-based file describing what the web service does to the client application. With this WSDL document, the client application will know where the web service is located and how to use it.
• UDDI (Universal Description, Discovery, and Integration): UDDI is a discovery of Web services and publishing of Web services in the discovery type of repository. One of the possible functionality deliverables includes the ability to let a service provider advertise their services and enable the consumers to search for services that they need.
• REST (Representational State Transfer): REST is a working model or, more accurately, a set of standards for building web applications. While the SOAP type of web service messages use the XML language and are based on complex protocols, the REST type of SaaS messages utilizes the HTTP standards and interchange data with the help of JSON.
• HTTP (Hypertext Transfer Protocol): HTTP is a protocol that is used when working with the WWW, to exchange information between the clients’ and the servers’ sites. The protocol is often used for Web services right now – both for services based on SOAP and REST.
• JSON (JavaScript Object Notation): JSON is an easy-to-read data format for the exchange of data that is particularly used in REST-based web service systems. A specific type of markup language, it is more compact than XML and is consistently chosen for its suitability and convenience.

How Do Web Services Work?

1. Service Description (WSDL)

• Publishing the Service: According to the need of the service provider, the provider needs to publish the web service with WSDL (Web Services Description Language). This information contains the name of the service – or its location, the operations that enable it, the messages passed between such services, and the data types employed.
• WSDL Document: This document represents a legal and digital agreement between the specific service provider and the service consumer as to the ways of accessing the service.

2. Service Discovery (UDDI)

• Registering the Service: To use web service, the service provider first needs to list his service in the UDDI (Universal Description, Discovery, and Integration). This is like a registry that shows where Web services can be published and found.
• Finding the Service: UDDI is used to register and discover a web service where the service consumer has to search for the most appropriate match. The Ws registry contains information about the application services and their respective WSDL.

3. Service Invocation (SOAP/REST)

SOAP-based Web Services:

• Request Creation: The service consumer, to execute the service, will generate a SOAP request message. Communicated below is the content of the message in XML and it is compliant with the structure defined within the WSDL document.
• Sending the Request: The SOAP message is transferred over a network protocol over the web to the service provider who has an endpoint.
• Processing the Request: The service provider then takes the SOAP request and completes the required service on the message received from the requester.
• Response Creation: After it performs the requested operation, the service provider has to construct a SOAP response message to return it to the consumer.

RESTful Web Services:

• HTTP Methods: Remisable services let developers leverage standard HTTP operations such as GET, POST, PUT and DELETE. Each method represents the type of performed operation on the data – read, write, modify, delete.
• Request Creation: The service consumer forges an HTTP request usually with a JSON containing an expected language in the body of the request and specifying a URI for the target resource.
• Sending the Request: This call is made in the form of an HTTP request sent to the endpoint of the service provider.
• Processing the Request: The end-user’s HTTP request reaches the service provider where the server processes the request and performs the necessary operation to respond.
• Response Creation: The service provider returns an HTTP response in most cases, which includes a JSON body that contains the requested data or the status of the process.

4. Data Interchange (XML/JSON)

• XML: This specification is mainly applied to SOAP-based web services; however, XML formats the request-response messages in such a way that they can be easily readable as well as programmatically processible.
• JSON: As far as its application is concerned, JSON is mainly utilized in RESTful web services but it is quite compact and is relatively easier to parse as compared to XML due to these reasons the JSON format of data is quite suitable for web or mobile applications.

5. Service Security

• SSL/TLS: Protect messages transferred between the consumer of a service and the provider by enciphering them.
• WS-Security: Safeguards the SOAP messages by enhancing the protocol through aspects such as authentication, encryption, and digital signatures.
• OAuth: Mostly implemented in RESTful services to address a secure paradigm to control access to the user information so that third-party applications can access them without involving credentials.
• JWT: JSON Web Token is a compact, URL-safe means of representing claims to be transferred among two parties in a portable data structure payload.

Features of Web Services

1. Interoperability

• Cross-Platform Communication: The interoperation of applications within the integrated application incurs applications that are developed for two or more platforms and are coded in different languages. Web services help in this process.
• Standardized Protocols: They employ standard protocols which include: HTTP, XML, SOAP, and WSDL which enhance compatibility between the realms.

2. Extensibility

• Flexible Integration: One major advantage of web services is that they are highly interoperable and portable hence they can easily be incorporated into new applications in an organization without much alteration to existing systems and procedures.
• Modular Design: They are supposed to be developed in a rather logical manner, meaning that new features may be incorporated into the system without influencing any of the services.

3. Scalability

• Distributed Computing: Web services are easily portable over different platforms and can be implemented on different server instances so that issues with load balancing and failovers can be easily addressed.
• Horizontal Scaling: They can be scaled horizontally towards bringing in more load by adding another instance of the service.

4. Reusability

• Service Reusability: Web services enable medium and large companies to modularize their business processes and use them in different applications with similar characteristics.
• Component Reuse: Services can be built on existing services making efficient reuse of software in the form of available services possible.

5. Loose Coupling

• Minimal Dependency: Web services are inherently asynchronous so that the Web service consumer and the Web service provider do not require entailment of implementations.
• Independent Deployment: This means that when a subtype is used instead of a more general type of service implementation on the server side, it is not necessary to change the client application as long as the interface is the same.

6. Discoverability

• UDDI Registries: To look for a particular service the services available can be registered and searched through UDDI registries, for the available services.
• Dynamic Binding: The consumers are also able to procure the services dynamically and offer their requests at runtime.

7. Security

• SSL/TLS: It is necessary to note that web services can employ SSL/TLS to provide secure communication over the World Wide Web.
• WS-Security: With the current services, we can achieve WS-Security standards such as message integrity, confidentiality and authentication with the use of SOAP-based services.
• OAuth: OAuth can be used for secure authorization in RESTful services.
• JWT: This is utilized in trustworthy messaging concerning RESTful services and identification.

8. Standardized Messaging

• SOAP: SOAP now has a messaging protocol that is articulated in XML which helps in preserving the structure and manner in which messages are handled.
• REST: REST employs conventional HTTP methods and status assertion, which contributes towards the reduction of the interaction model.

9. Support for Complex Operations

• Transaction Management: This means that web services can support multi-step and other types of complex transactions, which will guarantee the right flow of processes.
• Asynchronous Processing: They can operate asynchronously, and this can be useful when dealing with long-running operations since they can be worked on in the background.

10. Versatility

• Synchronous and Asynchronous: Web services may be either the request/response model, where a Web service sends back confirmation of the receipt of a request and information regarding how the request can be completed or the message-oriented model, where the two elements exchange messages independent of each other.
• Various Payload Formats: It works with different payloads, though most applications use either XML or JSON ones depending on the peculiarities of the given program.

11. Platform Independence

• Language Agnostic: The creation and use of Web services does not require the developer to use any specific language but should support Web standards.
• Protocol Agnostic: Web services can run on different transports although, the most typical transport is HTTP; other transports include SMTP and JMS.

Conclusion

In conclusion, web services are an important technology that fosters compatibility and interaction between applications across disparate platforms. They rely on industry-standard platforms and protocols such as XML, SOAP, and RESTful to ensure good interoperation. Important characteristics that clear its benefits such as reusability, loose coupling, and security raise flexibility and robustness in the new distributed systems. In conclusion, web services form a flexible and effective means of glueing together large and integrated, as well as interoperant, software environments.