What’s the difference between the REST API and Web HMI?


The OAS Platform REST API, like all APIs is a programmatic interface. It allows developers to read and write real time Tag data, read real time and historical Alarms and Trends, and even create or update Tag configurations. Because it utilizes JSON data over HTTP(s), it can be used by any virtually any development platform or language. It is also a perfect alternative to the .NET Data Connector for applications not running .NET code. Developers need to handle client to server communication to the API within their code. This includes web technologies such as Javascript, but if browser visualization is required, Web HMI may be the preferred product to utilize.

REST API Language Support

  • Any language that can support sending JSON over HTTP/S (.NET, PHP, Python, JS, NodeJS, Java, and more)
  • Fully documented and interactive API found here

Typical Applications

  • Automated solutions without the need for a user interface or data visualization
  • Programmatic configuration of the OAS Platform when using the .NET Data Connector is not possible (e.g. your platform is not .NET)
  • Native mobile applications

Skills Required

  • Knowledge of HTTP processes and methods
  • Familiarity with JSON object structures

Learn more about the OAS REST API >>


The Web HMI product is specifically geared towards web applications that need to visualize real time and historical data. It consists of a set of Javascript libraries intended to be included in your web pages which handle server communication and screen updates. While the Web HMI product does include programmatic methods for reading and writing Tag data, development is strictly done within HTML and intended to be run in a browser.

Web HMI Language and Platform Support

  • Any web application platform – built on standards (HTML, CSS, Javascript)
  • Any web development platform
  • Purely a Javascript solution for browser-to-OAS communications

Typical Applications

  • Real time and historical data visualization
  • System management and control user interfaces
  • Browser-based desktop and mobile applications

Skills Required

  • Web application development skills
  • Familiarity with JSON object structures
  • Javascript skills for direct access to the Web HMI script library functions

Learn more about OAS Web HMI >>

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