WSDL Introduction

One of the interactive formats for describing web services is WSDL and the full form for WSDL is Web Services Description Language. It was started and developed by Microsoft and IBM in March 2001. it is XML based language format used to describe functionalities and operations involved in web services. it basically tells the client application what the web services do. The general structure of WSDL consists of Definition, target namespace, Datatypes, Messages, Port-type, Bindings, and services. Actually, it looks very complex to any user, but it contains all the important messages or information that any client application would require to use the web services, but the more important thing is WSDL description is required without the client feeling difficulty understanding and moving forward.

History of WSDL

• The rise of WSDL 1.0 began in September 2001. It is jointly developed by Microsoft, Ariba, and IBM and consists of a combination of two service description languages and that is SDL which is from Microsoft (Service Description language) and Network application service specification language (NASSL) from IBM.
• Global Market approached the release of WSDL 1.0 in March 2001, WSDL 1.0 was formalized and released WSDL 1.1.
• In June 2003, WSDL acted as a working draft at W3C, by providing developers and managers with a user-friendly version.
• WSDL 1.2 turned into WSDL 2.0 with a predecessor of WSDL 1.1.
• In June 2007, W3C recommended WSDL 2.0.

What is WSDL?

The full form of WSDL is web services description language which acts as an XML-based language used to describe the operations and functionalities of web service. web services are the type of software components that allow applications to communicate with each other over any network typically using standard protocols like HTTP. It is divided into separate individual sections which actually specify physical details and logical design interface of a web service.

WSDL and its Documents

A WSDL document gives or defines the details of any web services. As I mentioned below are the elements associated with it.

• <types> - This particular element in web service is used to define the datatypes used in web services which acts as an XML schema implementation.
• <messages> - For each operation it outlines and defines the data elements in a web service associated with it.
• <binding> - We get to know what type of port is used and what data format can be analyzed using this element.
• <portType> - It describes all the operations used in a web service.

Key Features of WSDL:

1. It is platform-independent and has versatility features across various systems.
2. It plays an important component in UDDI (Universal Description, Discovery, and Integration).
3. It allows a systematic approach to define any web services.
4. As we all know it is an XML-based protocol that exchanges data and information in distributed systems.
5. It acts as a key support and tool to interface with XML services.
6. It also decreases the LOC (Lines of Code) which is used to access or to define web services.
7. In the SOAP domain, WSDL is used for node configuration.

Usage of WSDL

• It uses XML based approach to exchange information in a distributed and decentralized manner.
• It works in the combination of SOAP (Simple Object Access Control) and UDDI (Universal Description, Discovery, and Integration) protocols to provide web services.
• It is a language used to describe how to interface with XML services.
• When a client connects to the web server by using WSDL client can be able to determine what are the functions available on the server and by using SOAP he can one of the functions which is listed in WSDL.

WSDL patterns of operations

• One-way - Here the operation can receive a message, but the response will not be returned.
• Request-Response - Here the operation can receive a request and a response will be returned.
• Solicit-Response - In any operation, we can send a request and we need to wait for a response.
• Notification - In any operation, we can able to send a message, but we need to wait for a response.

Advantages of WSDL

1. Interoperability - It is a language-neutral and platform-independent. it allows the integration of diverse systems. It means that web services using WSDL can be consumed by applications developed in various programming domains and platforms.
2. Documentation - This provides a clear and structured description of service operations, their I/O parameters, and the protocols used. Documentation is helpful for developer and clients when they access the web server.
3. Discovery - It also facilitates service discovery. Clients find easy-to-understand web services by inspecting WSDL documents, which can be made public.
4. Tool - It is supported by a wide range of development tools which makes it easier for developers to create, analyze, and publish web services. The tools often generate code for working with WSDL documents.
5. Standardization - It helps to ensure consistency in describing web services, it also simplifies creating and consuming web services.

Disadvantages of WSDL

1. WSDL documents are somewhat complex, especially for large web services. The XML-based nature of WSDL maintains documents that may be error-prone.
2. WSDL consists of complex tooling and beginners may find it challenging to create or modify WSDL documents.
3. It has some alternative standards such as RESTful services, but some developers prefer human-readable alternatives to WSDL.
4. Version challenges by maintaining backward compatibility can be a challenge, particularly when evolving a service over time.
5. It creates additional overhead which can impact performance, especially in bandwidth-constrained environments.