- From: Didier PH Martin <martind@netfolder.com>
- Date: Mon, 17 Jan 2000 22:13:30 -0500
- To: "Mark Birbeck" <Mark.Birbeck@iedigital.net>, <www-rdf-interest@w3.org>
Hi Mark, Mark said: Only just spotted this - but I agree with you Didier. I've actually implemented a system using Microsoft's LDAP server to store XML nodes and RDF nodes. I'm not yet on Win2000 so I don't know if the performance will improve when I switch (and also use SQL 7), but at the moment it is not too good. However, the advantages of the ease with which I can change the meta data coupled with the resilience of LDAP have made me stick with it. I think the next piece of the jigsaw is the interface. I have written (or shall we say - am still writing!) a WebDAV layer over the LDAP. So far I can browse my XML with Microsoft's WebFolder client, and upload NITF documents which get broken into XML nodes, and then have loads of RDF added to them. Didier reply: I agree with you, going through LDAP to obtain a node is not fast. But it is faster if the converter and the server is on the same machine. Here is what I do and what are my goals: The goal is to provide LDAP content as XML to the outside world. My first try is to use RDF since the frame based pattern used by RDF seems to fit the frame based pattern of directory services. thus, a browser can do a request to an LDAP server and get back directory content through LDAP protocol. In that case, an LDAP protocol handler is necessary to convert the data received from the directory server into something displayable. We have actually implemented an LDAP protocol handler that works with IE 5. The protocol handler convert the LDAP data into RDF elements and these latter and further transformed into HTML by an XSLT style sheet. Thus, if the user do a view source, the XML formatted RDF content is displayed and, in the document viewer, the RDF elements are transformed into HTML and hence transformed into rendition objects. On the other side, the goal is to have also the directory data available as RDF documents under the HTTP protocol that, as you know, can pass through firewalls. In that case, the following query: http://www.netfolder.com/LDAP?O=W3C,C=US returns an XML document and more particular an RDF document containing about his <?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="http://www.netfolder.com/LDAP/style.xsl" media="screen"?> <rdf:RDF> <xml:base href="http://www.netfolder.com/LDAP"/> <rdf:description about="O=W3C,C=US"> frame content here.... </rdf:description> </rdf:RDF> We added the xml:base element so that each description is relative to the base. this way it is much easier to integrate the description into a new hierarchy like for instance: C=Country |____ S=State |____ O=Organization In the original taxonomy, W3C was classified as: C=Country |____ S=State To include the base in each description URI would impose to the RDF processor to extract the domain to only keep the important information (i.e. the element classification). Using the xml:base element we found that (a) each resource is not polluted by location information, (b) the description processing or inclusion into a new taxonomy is facilitated, (c) it is a lot easier to read also and more semantically significant. Our next step is that the server may recognize the user agent and do the XML -> HTML transformation client side or server side based on a client classification schema. For instance, a Netscape 4.x browser that do not have a clue of what XML is, the RDF document is transformed server side. if a client is an application, then the RDF document is delivered as is, idem if the browser is, for instance, IE 5.x. We found that this scheme works if an HTTP server is installed on the same physical server as the LDAP server. Then, the original LDAP server gets augmented by new capabilities by allowing access as usual through LDAP and also now through XML. By the way, if anybody is interested to test and play this new LDAP/RDF server, let me know, as soon as the alpha tests are finished, I can ship to you a copy to play with. On the other hand, I am producing a document about LDAP to RDF mapping, I will need review and constructive comments on the document. All collaborators name will be (with their consent) be included in the document. This could be, a good example of a practical application of RDF. And strange enough, directory services are meta data containers :-)) Didier PH Martin ---------------------------------------------- Email: martind@netfolder.com Conferences: Web New York (http://www.mfweb.com) Book to come soon: XML Pro published by Wrox Press Products: http://www.netfolder.com
Received on Tuesday, 18 January 2000 11:18:10 UTC