XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
Sublime Text - Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features. Fully customizable with macros, and syntax highlighting for most major languages.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
Notepad++ - A free source code editor which supports several programming languages running under the MS Windows environment.
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.
Eclipse IoT - Eclipse IoT provides the technology needed to build IoT Devices, Gateways, and Cloud Platforms.