xml parsing - What is the difference between SAX and DOM?

Question

I read some articles about the XML parsers and came across SAX and DOM.

SAX is event-based and DOM is tree model -- I don't understand the differences between these concepts.

From what I have understood, event-based means some kind of event happens to the node. Like when one clicks a particular node it will give all the sub nodes rather than loading all the nodes at the same time. But in the case of DOM parsing it will load all the nodes and make the tree model.

Is my understanding correct?

Please correct me If I am wrong or explain to me event-based and tree model in a simpler manner.

Answer 1

Well, you are close.

In SAX, events are triggered when the XML is being parsed. When the parser is parsing the XML, and encounters a tag starting (e.g. <something>), then it triggers the tagStarted event (actual name of event might differ). Similarly when the end of the tag is met while parsing (</something>), it triggers tagEnded. Using a SAX parser implies you need to handle these events and make sense of the data returned with each event.

In DOM, there are no events triggered while parsing. The entire XML is parsed and a DOM tree (of the nodes in the XML) is generated and returned. Once parsed, the user can navigate the tree to access the various data previously embedded in the various nodes in the XML.

In general, DOM is easier to use but has an overhead of parsing the entire XML before you can start using it.