An XST file is a template used by WebSphere Application Server (WAS), a server program that hosts Java-based web applications. It typically contains an SQLtoXML Java class, database connection information, and an SQL query. XST files are used to generate XML data from SQL database queries.
IBM WebSphere is a collection of Enterprise programs released in 1998 that enabled users to develop applications and integrate them with other programs. You will most likely only encounter WebSphere Query Template XST files if you are a developer creating Enterprise web applications hosted by WAS.
If you need to open a WebSphere Query Template XST file, you can use an XML editor since the files are stored in XML format. You can also create and edit WebSphere Query Template XST files with an XML editor, such as Microsoft Visual Studio Code, Microsoft XML Notepad, MacroMates TextMate, XMLBlueprint XML Editor, or SCREEM.