Reinhard Poetz wrote:From: AlanYup. Alan, take a look at the XMLDBSource and XMLDBSourceFactory. I think you'll find them reasonably similar to what you might want to do (in src/blocks/xmldb/java/org/apache/cocoon/components/source/impl)Working on it. As noted, I have JAXP implemented and SAX interface to XUpdate. I have APIs. I am going to start working on services next. A Cocoon generator that takes a Momento data source and an XSLT transform would be a start.
I'm not sure how to get information into Momento via Cocoon. I'm
thinking about some sort of Woody binding, but that goes beyond
my current understanding of Cocoon.
speaking without following this thread closly: What about implementing a Momento source?
If you implemented a MomentoSource, and made it implement ModifiableSource, then you would be able to read/write from within Cocoon. With this, you would be able to use Woody's binding functionality to bind forms directly to Momento data.
You could also do something like the XMLDBTransformer to allow updates (src/blocks/xmldb/java/org/apache/cocoon/transformation/XMLDBTransformer.java).
[NB. with an XML:DB interface to Momento, you wouldn't need to do anything to interface to Cocoon].
Hope this helps.
Regards, Upayavira
I agree with the above suggestions and would like to provide some more technical details.
Pseudo protocol ===============
In Cocoon (or actually Avalon Excalibur), we have a generalization of protocols, java.net.URL, called pseudo protocol org.apache.excalibur.source.Source, there are also various extensions of Source like ModifiableSource, TraversableSource among others. Pseudo protocols are an excelent way of separating the location of data with what to do with it. If you package a data source as a pseudo protocol you can access it by using its URL, e.g. momento://dbpath/collection#xpath(foo/bar), through Cocoons source resolver. This makes it possible to use sources for ala src attributes in the sitemap, the document function in XSLT and XQuery, hrefs in the [X|C]IncludeTransformer, in the SourceWritingTransformer and within flowscripts.
A MomentoSource would thus give a lot of flexibility in using Momento in Cocoon. Especially if it allows using XPath(2.0) in the URLs and if it is a modifyable source.
XSLT ====
A MomentoSource would also give a good way to use Momento together with XSLT and XQuery in Cocoon. Here we need to extend the ordinary use of sources somewhat, let me explain:
The Source interface provides a getInputStream method, in Cocoon some Sources implements org.apache.excalibur.xml.sax.XMLizable that provides a toSAX method as well. SAX or Streams are probably not the most efficient way to communicate with an XML db, so to make the pseudo protocol idea usable together with Momento, we should provide a way to get a DOM structure from a pseudo protocol. This could be done by introducing a new interface:
interface DOMizable {
org.w3c.domNode getNode();
}or something similar. If the MomentoSource implements DOMizable, we have direct access to nodes in the XML db.
Now we are prepared to connect Momento to XSLT. In Cocoon we can use Saxon through the org.apache.cocoon.transformation.TraxTransformer, you just need to change cocoon.xconf a little bit to use Saxon instead of Xalan. There is also a TraxGenerator in the scratchpad that could be used with some small modifications.
I would guess that Momento mainly would be accessed through the document function in XSLT and XQuery. Saxon use JAXP 1.1 as external API to the transformerand the URLs in the document functions are resolved by using an implementation of javax.xml.transform.URIResolver that is provided by the TraxTransformer.
The implementation of the URIResolver that is used is org.apache.excalibur.xml.xslt.XSLTProcessorImpl in its current incarnation it uses the exclaibur source resolver to get the source and then it returns a javax.xml.transform.stream.StreamSource. For use with Momento we need an implemetation of URIResolver that checks if the the source is DOMIzable and in that case returns a javax.xml.transform.dom.DOMSource instead. This can be done by extending the excalibur XSLTProcessorImpl and change the XSLTProcessor in cocoon.xconf.
XQuery ======
XQuery in Saxon use a propertary api, (there are no standard in this area yet). So we need a specialized SaxonXQueryGenerator. Saxon use the JAXP URIResolver for XQuery also, so the above described mechanisms can be used here as well. Unfortionatly Saxon is MPL 1.0 that is not compatible with ASL, so we cannot have Saxon as a part of Cocoon :(
--- o0o ---
Sorry for all the technical details ;)
As you can see, for reading from Momento, the only Momento specific code is in the MomentoSource, everything else is using DOM, JAXP and Cocoon APIs. Therefore the proposed mechanisms would give an efficient way of using XSLT and XQuery on all data structure that have a DOM interface and is accessable through a pseudo protocol. See the thread: [RT] the quest for the perfect template language http://marc.theaimsgroup.com/?t=104930795600004&r=1&w=2 for a long disussion around related ideas.
I would love to see the proposed mechanisms in Cocoon.
/Daniel
