I use filters quite a lot, filters as supplied by the language (Perl and Shell), or filter frameworks written by me (Python). From what I have learned, your design is far too ambitious - you don't need an XML schema to store information about objects. You want your filters to comply to a simple, common interface - don't try to make filters optimize their connections, simply build optimized filter-pairs if you need them.

The filter pipeline setup can be well stored in an XML file, but if your interface is as simple as I recommend, there is not much difference between an XML file and your program, as most of your programming becomes declarative. To illustrate this, here is a small module/program, that filters a list out of one of our hosts into a csv file (Python code ahead) :

if __name__ == '__main__':
        InputFilename = sys.argv[1]

        output= Pipeline(
                FileFilter(),
                WVS19502Filter(),
                Date(["Valuta","DD.MM.YYYY"]),
                apply(Kommazahl,columns),
                SimpleCSVOutputFilter(["Broker","Valuta","Waehrung"]+c
+olumns,","),
        ).run(files(InputFilename))

        OutputFilename = "../OUTPUT/"+os.path.basename(InputFilename)+
+".csv"
        out = open(OutputFilename,"w")
        out.write(string.join(["Broker","Valuta","Waehrung"]+columns,"
+,")+"\n")
        for i in output:
                out.write(i["line"]+"\n")
        out.close
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As you see, except for the setup and the output, everything is declarative. The interface each filter supports is simply two methods :

• constructor() - all relevant parameters for operation are passed to the constructor.
• process() - this method processes an array of hashes into another array of hashes. Each row of data is organized as a hash to easily allow adding / removing / permutating the data.

As for the language of implementation, this concept can be implemented in almost any language, as it neither requires reflection nor multiple inheritance. If you're looking for a resource-eating multithreaded parallel implementation, you will feel at home in both languages, but as the interface is so simplicistic, the type-enforcement of Java will buy you nothing.

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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