XSD files are so-called XML schema definitions. Among other things, they specify which elements and attributes may appear in an XML file, as well as the relationship between elements and their data type. In addition, new data types can be defined or existing ones expanded, which can then be used in XML files.
XSD files are pure text files that can be viewed and edited in any text editor. However, it is recommended to use an XML editor.
Most often resolving problems with opening XSD files is very simple. Just install an appropriate program that supports such files. All of the listed programs support XSD files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of XSD files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate XSD files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the BBEdit applications is not on the list, select "Browse" option in order to manually locate the directory where BBEdit has been installed.
Sometimes problems with opening XSD files may not lie with the application itself, but can arise due to other causes, such as: