Editing XML (section)

=== Pull parsing ===
Pull parsing treats the document as a series of items read in sequence using the [[Iterator pattern|iterator design pattern]]. This allows for writing of [[recursive descent parser]]s in which the structure of the code performing the parsing mirrors the structure of the XML being parsed, and intermediate parsed results can be used and accessed as local variables within the functions performing the parsing, or passed down (as function parameters) into lower-level functions, or returned (as function return values) to higher-level functions.<ref>{{cite web|url=http://www.xml.com/pub/a/2005/07/06/tr.html|title=Push, Pull, Next!|first=Bob|last=DuCharme|website=Xml.com|access-date=16 November 2017}}</ref> Examples of pull parsers include Data::Edit::Xml in [[Perl]], [[StAX]] in the [[Java (programming language)|Java]] programming language, XMLPullParser in [[Smalltalk]], XMLReader in [[PHP]], ElementTree.iterparse in [[Python (programming language)|Python]], SmartXML in [[Red (programming language)|Red]], System.Xml.XmlReader in the [[.NET Framework]], and the DOM traversal API (NodeIterator and TreeWalker).

A pull parser creates an iterator that sequentially visits the various elements, attributes, and data in an XML document. Code that uses this iterator can test the current item (to tell, for example, whether it is a start-tag or end-tag, or text), and inspect its attributes (local name, [[XML namespace|namespace]], values of XML attributes, value of text, etc.), and can also move the iterator to the next item. The code can thus extract information from the document as it traverses it. The recursive-descent approach tends to lend itself to keeping data as typed local variables in the code doing the parsing, while SAX, for instance, typically requires a parser to manually maintain intermediate data within a stack of elements that are parent elements of the element being parsed. Pull-parsing code can be more straightforward to understand and maintain than SAX parsing code.