Define validating parser major events occurred in iran dating back to 2016 bce
building the full AST of an XML document for convenience of the user, SAX parsers operate on each piece of the XML document sequentially, issuing parsing events while making a single pass A SAX parser only needs to report each parsing event as it happens, and normally discards almost all of that information once reported (it does, however, keep some things, for example a list of all elements that have not been closed yet, in order to catch later errors such as end-tags in the wrong order).
Thus, the minimum memory required for a SAX parser is proportional to the maximum depth of the XML file (i.e., of the XML tree) and the maximum data involved in a single XML event (such as the name and attributes of a single start-tag, or the content of a processing instruction, etc.). A DOM parser, in contrast, has to build a tree representation of the entire document in memory to begin with, thus using memory that increases with the entire document length.
While a SAX parser may well be used to construct such a tree initially, SAX provides no help for such processing as a whole.
Additionally, some kinds of XML processing simply require having access to the entire document.
The result above may vary: the SAX specification deliberately states that a given section of text may be reported as multiple sequential text events.
Many parsers, for example, return separate text events for numeric character references.
SAX provides a mechanism for reading data from an XML document that is an alternative to that provided by the Document Object Model (DOM).
Where the DOM operates on the document as a whole, i.e.
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The event-driven model of SAX is useful for XML parsing, but it does have certain drawbacks.