Web Services are a type of software interface in an information system, enabling the provision of functions and data on the web. This facilitates communication and integration among different systems, such as web applications, application servers, mobile apps, desktops, and the Internet of Things (IoT).

Their use lies in the need for communication and data exchange in the form of JSON or XML systems, especially when they are constructed in different programming languages and are located in different geographic locations. This is achieved through the web using the HTTP protocol.

So, an application on the internet node, built in one programming language, can communicate with a second application on the same server or in a different programming language, even when it is located on a different computer or node or IoT device, exchanging data. Generally, web services are associated with Service-Oriented Architecture (SOA).

These services use HTTP methods:

  • GET: Retrieves data from a source.
  • POST: Sends data to the server to create data.
  • PUT: Updates the data of the source.
  • DELETE: Deletes data.
  • HEAD: Similar to GET but used to check what GET will return.
  • OPTIONS: Describes the methods available in a source.

The above interactions are the basics that a web developer should know to use APIs (consuming) when there are no corresponding libraries for them.

Machine-to-Machine Communication (M2M)

Suppose the second application needs to use some of the functions of the first. The primary challenge is that these applications are written in different languages, and a way must be found for the second application to communicate with the first.

The method of communication between applications stems from Web Services technologies. Specifically, a web service runs on a server that listens for requests on a specific port and responds by sending data in XML, JSON, or HTML format.

The three main technologies of Web Services are REST (Representational State Transfer), XML-RPC (Remote Procedure Call), and SOAP (Simple Object Access Protocol).


RESTful Web Services:

In REST, we already have all the means to make the two applications communicate. This is done through HTTP, where services are provided with URIs (resources) that use HTTP methods such as GET, POST, PUT, and data is included in JSON or XML format.

The standard for successful RESTful API development is the OpenAPI Specification, serving as a programming language-agnostic interface for describing HTTP APIs.


The second technology, XML-RPC, uses remote procedure calls over HTTP using XML encoding. In other words, it allows calling a specific function of an application located on a different computer using specified parameters, as opposed to REST, which uses data.


The third type, SOAP, is similar to XML-RPC, with the difference that it supports more data types and is endorsed by major companies. All well-known companies providing cloud services, such as Amazon Web Services and Google Cloud Compute Products, offer access through this technology.

Its structure is simply an XML document consisting of the following parts:

  • Envelope element: Declares that the XML is of SOAP type.
  • Header element: Contains information about authentication, etc.
  • Body element: Contains the call elements and the expected response.

OData (Open Data Protocol)

This protocol is a form of REST API, with the difference that it focuses on business logic. Therefore, it is used by popular ERPs such as SAP ERP and Microsoft Dynamics for system integration with systems such as an e-shop or other services to provide increased capabilities and data enrichment in what we call API economy.

The OData protocol is used to create RESTful APIs to implement best practices.

So, if you need to create APIs for your business to provide programmatic access to others or to use popular services' APIs, you can hire a web development specialist.

What is API

Here, we would like to emphasize that all web services are APIs, but not all APIs are web services. Specifically, an API is an interface that makes the application's data available to other software. If you need web developer call us.