Unlike relational tables, which are relatively straight forward, XML structures can be quite complex, and span multiple files or locations. In short, there are more "moving parts" when dealing with XML, and each part has to be correct and consistent with the other parts.
When XML errors are encountered, there are several immediate areas to consider and verify.
Does the XML data match the schema?
Does the data match the PowerCenter metadata definition?
For multi-file schemas, are the files and relative file path references matching?
Are all the expected files present?
The error messages displayed in the Data Validation Option screens are the first place to look.
For example, the following error message indicates that the data does not match the schema. An element in the XML file is not defined in the XML definition.
In the following example, the message indicates that the expected XML file is not present. This means the file could be missing, the file name could misspelled, or the directory or path was entered incorrectly.
Use of Multi-file schemas could also cause these types of errors if the relative file paths are not correct.
These are the easier problems to solve because they follow well defined patterns and error messages are reasonably specific.