To enable the XML Development capability, select Window > Preferences from the workbench menu bar to open the Preferences dialog box. In this dialog box, choose General > Capabilities and, in the resulting Capabilities page, ensure that the XML Development capability is selected.
Debugging XSL transformations does not require that the XSLT stylesheet, XML input document, or supporting documents (such as includes and imports) be in a project. However, the debugger uses the project specified in the Main tab of the launch configuration to find source. If no project is specified in this tab, or if the project does not contain all of the documents used in the transformation, add their location to the source lookup path in the launch configuration Source tab. The source lookup path can also be modified after launching by selecting the debug target (or a thread or stack frame) in the Debug view, right-clicking and selecting Edit Source Lookup from the pop-up menu.