On Mon, Jun 8, 2009 at 20:39, John Millikin<jmillikin@gmail.com> wrote:
I'm trying to convert an XML document, incrementally, into a sequence of XML events. A simple example XML document:
<doc xmlns="org:myproject:mainns" xmlns:x="org:myproject:otherns"> <title>Doc title</title> <x:ref>abc1234</x:ref> <html xmlns="http://www.w3.org/1999/xhtml"><body>Hello world!</body></html> </doc>
The document can be very large, and arrives in chunks over a socket, so I need to be able to "feed" the text data into a parser and receive a list of XML events per chunk. Chunks can be separated in time by intervals of several minutes to an hour, so pausing processing for the arrival of the entire document is not an option. The type signatures would be something like:
type Namespace = String type LocalName = String
data Attribute = Attribute Namespace LocalName String
data XMLEvent = EventElementBegin Namespace LocalName [Attribute] | EventElementEnd Namespace LocalName | EventContent String | EventError String
parse :: Parser -> String -> (Parser, [XMLEvent])
I've looked at HaXml, HXT, and hexpat, and unless I'm missing something, none of them can achieve this:
+ HaXml and hexpat seem to disregard namespaces entirely -- that is, the root element is parsed to "doc" instead of ("org:myproject:mainns", "doc"), and the second child is "x:ref" instead of ("org:myproject:otherns", "ref"). Obviously, this makes parsing mixed-namespace documents effectively impossible. I found an email from 2004[1] that mentions a "filter" for namespace support in HaXml, but no further information and no working code.
I would recommend hexpat to do the job. Contrary to what you are saying, hexpat does offer namespace handling: http://hackage.haskell.org/packages/archive/hexpat/0.8/doc/html/Text-XML-Exp... Perhaps you need more than that? Personally I found hexpat to be fast, space efficient and easy to use. Here is the representation I got for your example. Please note the namespaces in right places. * > (toNamespaced ( toQualified t')) Element {eName = NName {nnNamespace = Just "org:myproject:mainns", nnLocalPart = "doc"}, eAttrs = [(NName {nnNamespace = Just "http://www.w3.org/2000/xmlns/", nnLocalPart = "x"},"org:myproject:otherns"),(NName {nnNamespace = Just "org:myproject:mainns", nnLocalPart = "xmlns"},"org:myproject:mainns")], eChildren = [Text "\n",Text " ",Element {eName = NName {nnNamespace = Just "org:myproject:mainns", nnLocalPart = "title"}, eAttrs = [], eChildren = [Text "Doc title"]},Text "\n",Text " ",Element {eName = NName {nnNamespace = Just "org:myproject:otherns", nnLocalPart = "ref"}, eAttrs = [], eChildren = [Text "abc1234"]},Text "\n",Text " ",Element {eName = NName {nnNamespace = Just "http://www.w3.org/1999/xhtml", nnLocalPart = "html"}, eAttrs = [(NName {nnNamespace = Just "http://www.w3.org/1999/xhtml", nnLocalPart = "xmlns"},"http://www.w3.org/1999/xhtml")], eChildren = [Element {eName = NName {nnNamespace = Just "http://www.w3.org/1999/xhtml", nnLocalPart = "body"}, eAttrs = [], eChildren = [Text "Hello world!"]}]},Text "\n"]} Best regards Krzysztof Skrzętnicki