From the large number of articles on XML with a focus on gambas, the following articles can be recommended, although the order is not ranked:
You should know XML as a way to read or store data in a structured way and then share it securely with others. Exactly in this direction Linus Thorvalds is to be understood if he remarks in an essay:“Using XML only because it's chic is nonsense. XML only if you pass on data and let it be edited and the result is passed on again, etc.! To do this, however, you must insert a reference to a suitable XSD schema in an XML file in order to always process valid data.
Gambas provides you with several components with many classes for writing, reading and parsing XML files. Both SAX (Simple API for XML) and DOM (Document Object Model) are offered as interfaces for accessing the content of an XML file.
The complete description of the classes with their properties, methods and events can be found in this chapter. The understanding for the implementation of the theory shall be supported by the description of many projects.