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)?
• etc.

There are 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.

Speed

​Speed comparison of different XML parsers

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

Final

I will use expat, because of the decision for SAX, the speed and it is more secure than Xerces.