The very first task is to choose XML parser that will be used as a foundation of the KML driver. There are many questions that have to be answered:

• SAX or DOM?
• provide XML validation for KML documents (mandatory, optional, none)?
• ...

There are 3 or 4 XML parsers under our consideration:

• ​Expat
• ​Xerces
• minixml​
• ​libXML

Here is very ​detailed comparison (made in 2003) of XML parsing libraries that may be helpful during the analysis.

Feature	Expat	Xerces	minixml	libXML
Parser	​SAX	SAX, ​DOM	DOM	DOM
Validating	no	yes	no	yes (w/o reparsing)
Encoding	UTF-8	UTF-8/16,ASCII,latin1	ASCII/UTF-8	UTF-8/16,ASCII,latin1
Library size	150KB	~4MB	built-in	~1MB
Thread safe	yes	yes	yes	yes
Used in GDAL part	OGDI	GML, ILI	many places	not yet
Secure *	yes	no
...	...	...	...	...

* Google avoids Xerces because it considers it to be insecure in the face of hostile XML documents, but considers Expat safe. Presumably based on an indepth security review.

SAX or DOM

Which technic should be used for reading the KML files?

• I (Jens) guess SAX would be best, because of the memory consumption of DOM
• SAX is more complex to use in case of KML