Question

What are the two basic XML parsing models? Describe how they are different from each other and when each might be used.

Answer 1

There are two basic types of XML parsing models-
1) DOM (Document Object Model)
DOM is a tree-based model that creates an internal strcuture of the XML document as a tree of nodes. This tree can be searched for nodes, and these nodes can be read and updated by the client application.
DOM model is generally used for small documents, because it is memory inefficient, since it uses up more memory for loading whole XML document into memory.
DOM models are commonly used for browsers, editors etc.
2) SAX (Simple API for XML)
SAX is an event-driven model. It doesn't create any internal structure of the XML. Instead, an event-based API sends parsing events directly to the client application through callbacks, and the application implements handlers to deal with the different events. In SAX, it is not possible to navigate through the document like with a DOM model. Also, SAX is read only i.e. can’t insert or delete data.
SAX models are generally used for large documents as they memory efficient (uses up no extra memory to store XML document content) as comapred to DOM models.