> I realized that some unix system distribution does not provide xmlwriter.h in standard libxml2-devel 
> package.
> 
> For instance, scientific linux (also PSI linux) does not.
> I installed it from source.
> 
> Macintosh has xmlreader.h by default, and does not xmlwriter.h.
> I installed it by using FINK.
> (FINK is a unix package porter like CYGWIN.)
> 
> Someone may ask about it someday. 
> A problem is that compiler will find xmlwriter.h even if the system does not have it, because ROME has.
> This may make it hard that users find out the problem.
> 
> 
> How to install libxml2.
> ----  UNIX OS ----
> In most cases, to use standard way of the system is good. But some system does not provide xmlwriter.h. In this case you may need to 
> install it from source.
> 1. download source from <a href="http://xmlsoft.org/">http://xmlsoft.org/</a>.
> 2. decompress it and go to created directory.
> 3. % ./configure [options as you like];
> 4. % make;
> 5. become super user, if you are going to install it in system.
> 6. % make install
> 
> ---- MacOSX ----
> By default, Macintosh does not have xmlwriter.h. You can follow the same way as other UNIX OS. And other way is to use FINK. (I hope 
> many users already installed it.)
> 1. install FINK (<a href="http://fink.sourceforge.net">http://fink.sourceforge.net</a>)
> 2. become super user.
> 3. apt-get update;
> 4. apt-get install libxml2 libxml2-shlibs libxml2-bin
> If you are goint to use also MySQL.
> 5. apt-get install mysql12-dev mysql12-shlibs
> (* package name can be changed in future, you may find it with "apt-cache search libxml2" or "apt-cache search mysql")

I have replaced libxml with mxml (written by Stefan) which is now included in the rome distribution.
So there's no install problem on linux anymore.