Speakers: Mark Reinhold (MarkR) and Larry Cable (LarryC)

Moderator: Edward Ort (MDR-edort)

This is a moderated forum.

MDR-edort: Welcome to Java^TM Live. Today's topic is XML and the Java 2 Platform. Our guests are Mark Reinhold and Larry Cable. Both are working on adding XML support to the the Java 2 Platform. Mark is here. We're waiting for Larry. So let's begin. Who has the first question?


Sasha Nakhimovsk: When will the XML packages become a standard extension? How long will it take between the release of XSLT recommendation and Sun's support for XSLT?

MarkR: We have several active efforts to add XML support to the Java platform. As we announced at JavaOne^SM, the first extension containing "basic plumbing" APIs (i.e., a SAX parser and an implementation of the DOM) is targeted for release near the end of this calendar year. We're tracking the XSL/T work -- Larry Cable is a member of the W3C working group -- but I really couldn't say exactly when we'll have support for that.


Byron: Is there a good place to find DTD's already developed for various purposes and industries?

MarkR: You can find a large list of existing applications of XML, including some schemas and DTDs, under the pages maintained by Robin Cover for OASIS. I think the URL is oasis-open.org, or if you visit the W3C's XML pages you can find a link there. Eventually xml.org will be a central repository and registry of DTDs, but I don't think they have any available yet.


John Abjanic: Will there be a parsing API?

Chirokikh: You can also look at www.xml.com.

LarryC: The short answer is yes, the slightly longer version of it is that the first release of the optional package for XML will include support for the W3C DOM Level 1 Java programming language binding and SAX V1.0 (from David Megginson & XML-DEV). These API's will have a (pluggable) parser behind them.


John Abjanic: Will there be support for XML-schema and XML-data in the API?

Mojo Jojo: What about Simple API for XML (SAX) 2.0 support?

MarkR: The initial extension will only support SAX and DOM parsing. The XML data-binding project, which I'm leading, will support schemas by compiling them into Java classes.


kuni: At JavaOne, you guys talked about a mechanism you're developing to be able to bind XML to Java classes. Any updates on this effort?

LarryC: What about SAX 2.0 support? Well we are tracking the SAX 2.0 efforts, but we want to get our 1st release out asap, if SAX 2.0 solidifies in time then we would consider it for 1.0, but at this point it's more likely that SAX 2.0 will come in a revision of extension next year ...


David M: We have been using Document Object Model (DOM) and SAX parsers. As documents get large the SAX parser gives us more scaleability, will you be supporting both DOM and SAX?

LarryC: YES!


Malin: Will Sun provide an XSL engine?

MarkR: An update on binding: The JSR (Java Specification Request) for this is just about ready to be submitted. Look for it on the Java Community Process web site "real soon now." We'll also release a whitepaper at the time of the submission.


Mike Azzi: In The JavaOne XML presentation you mentioned support for the XML Schemas standards for application level parsing. Is this going to be part of the first extension? What about support for DOM level 2?

MarkR: No, support for schema-to-Java bindings will not be part of the first extension. We'll support DOM level 2 once it's standardized, but it seems to be pretty far from that point right now.

LarryC: Will we support XSL? The short answer is YES! The longer answer is that we are in the early stages of planning, but what we are most likely going to do is provide an XSL engine "invocation" API as a std extension providing a portable API to invoke a Stylesheet on a document. Also we would of course provide an implementation of an engine under that ... but that will not happen until next year.


David: Is any plan to support XML ( with XSL ) web browser for HotJava^TM or the Java Foundation Classes (JFC) Project Swing package?

ab: By when can we expect data-binding and schema support?

LarryC: Is there a plan to support XML/XSL in HotJava or JFC Project Swing? There are no current plans, however since the proposed extensions for XML are 100%PureJava^TM, you will be able to use them in conjunction with both environments ...

MarkR: We can't promise any dates for the data binding project just yet. We're still in the prototyping stages, and besides the W3C XML Schema working group is not expected to finish its work until the end of the year.


David M: Do your XML plans extend to the KJava^TM VM*?

Bram: Are you working with IBM (and their XML/XSL teams) to develop these things, or are you re-engineering these from scratch?

ricardo: How often do you guys offer these sessions. I am currently a new user trying to get a handle on the Java technology.

LarryC: Are we working with IBM? Yes, we work very closely with IBM, and all of the other members of the W3C, and XML.ORG. We are also working with a number of other experts as part of the JCP process to create the std extensions.

MarkR: On KJava: Currently Larry and I are focussing our efforts on the J2SE and EE (standard and enterprise) platforms. I've heard that the KJava team is looking into XML support, but I don't know much about it.

MDR-edort: Response to Ricardo. We try to have these Java Live session at least once a month. Sometime we'll hold them more often depending on the availability of guests. We also hold online "Office Hours" sessions that allow you to ask questions to authors of articles and tutorials on the JDC.


Byron: Could you elaborate more on what you mean by "compiling them into Java classes"?

MojoJojo: I notice that mozilla.org has, as part of its Java integration, a way to access DOM from applets. Will that be part of the standard extension? I'd like the code I'm writing in the Java programming language to do what my JavaScript code can already do ...

LarryC: Re: Mozilla ... can you tell me more about the nature of the integration, is it exposing the browsers DOM of the current page into the Applet?


Sasha Nakhimovsk: Sun has an excellent tutorial on using XML and the Sun parser, but there's no way right now to download the entire tutorial. Could this be arranged?

MarkR: In answer to Byron: The basic idea of data binding is to look at an XML schema and translate it into a set of Java classes that reflect the structure and type information in the schema. The classes also handle all of the messy parsing and formatting issues, so you can write an XML-aware application without having to learn the SAX and DOM APIs. For more information, you can see the slides from our JavaOne talk (under http://java.sun.com/javaone) or the forthcoming JSR and whitepaper for the data-binding project.


Mike Azzi: OK, here's a question that regards the XML per se. But I thought you guys might be on the standards committee, and you might know the answer to this. Is the XML standard ever going to allow parsed data in the attribute field? This feature can be very useful in XML compliant JavaServer Pages^TM (JSP).

Bram: (Will this session be archived?)

LarryC: Re: tutorial download, that's something we have been asked for before and we are working on it!!! .... so watch that space/URL!

MDR-edort: Answer to Bram. It will be archived immediately after the session ends.

LarryC: MojoJojo: I don't think we have any plans to date to expose the browsers DOM to an Applet as part of this effort ... but it's something for us to think about!


kuni: I see that XSchema support is pending the W3C WG's completion of the spec. At the XML BOF at JavaOne, you mentioned that regular expression parsing would likely be added to the core API to support XSchema in the future. Will this only become available in conjunction with XSchema support?

MojoJojo: (Suffering from this chat client) ... Mozilla's exposing the browser's DOM to an applet, yes. There's an MT related restriction (only an event callback thread can use it, I think) for the moment. Information available on-line, and some Sun folk are working on that part of mozilla.

MarkR: In reply to Mike Azzi: I don't think that the XML spec itself will ever have a richer notion of types for attribute values. In the W3C Schema working group, however, we're working on draft specifications that allow a fairly rich set of constraints to be expressed for both attribute values and element content. (If this isn't what you mean by "parsed data," please elaborate.)

MDR-edort: To MojoJojo in ref to "suffering" ... we're aware of the applet's problems and we're planning to provide a better tool fairly soon.

LarryC: MojoJojo: that's what I thought they were doing ... exposing the page DOM into the Applet ... that would require an extension to the Applet API ... but it's worth thinking about since browsers have evolved to a stage where this may be possible in a portable fashion.

MarkR: Re. regular expressions: There's been a lot of demand for this feature over the years. Given the generality of regular expressions it would be a bit odd, I think, to only support them as part of the data-binding facility -- it really seems like something that belongs in the platform. It's too early to say, however, in exactly what form regex support will appear.


MojoJojo: (To Edward O in ref to 'suffering') ... good! It seems to die and hide data, plus scrolling one line sometimes jumps a screen and hides what I was trying to see!

MDR-edort: You might try viewing the session in unformatted mode.

LarryC: Who is using what; DOM (lvl 1 or 2)? SAX (1.0 or 2.0)? ... XSL???

MDR-edort: I've heard about Project X. How does it fit into your future plans?

LarryC: ProjectX is our technology release of SAX, DOM, namespace and parser support. Our current plans are to use this as the basis for the Std Extension Reference Implementation.


Byron: Thanks a lot MarkR, this is very helpful!

David: When will Project X be officially released?

LarryC: ProjectX is in TR2 (Technology Release 2) this is available for free from our website, and is licensed such that it can be used commercially. As I just stated we plan to use Project X as the basis for the Reference Implementation of the Std Extension for parsing (DOM, SAX ...) ... I can't say for certain when this RI will freeze ... but I would predict around the end of this millenium or early in the next! But you can start using it now!

MDR-edort: We've had a nice set of questions and answers so far. But right now there's no question in the queue. So if anyone has a question for Mark or Larry, ask it now.


Sasha Nakhimovsk: Are you monitoring/contributing to xml-dev list?

Mike Azzi: What I meant by "parsed data" is full XML Element nodes as an attribute that can be parsed. So that something like JSP's <%= ... %> can be implemented straight in an XML way.

LarryC: Yes we are monitoring xml-dev ... but we are currently focused on W3C ... Do you think we should be taking a more active role in that forum?

MarkR: Parsed data: I think it would be pretty counter to XML's goal of being (fairly) simple to be able to embed entire elements within an attribute. I'll let Larry speak to the JSP issue.

LarryC: Re: an XML form of JSP Scriptlet expressions ... we are currently thinking about an alternate syntax for scriptlet expressions in attributes when the JSP is an XML document.

MDR-edort: What plans do you have for support of XML in enterprise applications?


Mike Azzi: Are you contemplating any work on RDF which is also an XML application?

MarkR: RDF: We're not quite sure what to make of this yet. Some folks seem very, very interested and others not at all, so it's been hard to gauge the demand. We're tracking the RDF work but at the moment we have no concrete plans to support it.

LarryC: Re: XML support for Enterprise applications? Well the std extension that Mark and I are currently working on are pretty much a prerequisite for portable XML in any Java application. Once we have that in place then we will be working to update the Java 2 Enterprise Edition to provide greater support for using XML to describe and exchange enterprise data, within and between enterprise applications. Possible areas are JMS support, Enterprise JavaBeans^TM (EJB) support, and JSP support. One of the things I am looking at is the relationship of XSLT to JSP ....


Sasha Nakhimovsk: Re: xml-dev list: yes, I think it would be very useful if you/Sun were a presence there. Re: JSP: do you anticipate that JSP pages will become well-formed XML documents?

MojoJojo: Larry asked who's using what. Right now I'm mostly using SAX 1; it's simple enough, very low overhead, and gives me all the data I need. SAX 2 lets me find out more about the parser; I can take the default parser, ask if it validates, enable or disable validation, all without getting tied to some particular parser. DOM is too fat for me; and it's easy enough to make data structures that are much more efficient, and which tie better to my own tasks. Where I use DOM is for quick'n'dirty stuff where I'm working with small bits of data, and want a brainless printing scheme that won't have errors. XSL/T I've only played with. It's great for those dynamic content generation systems, where I construct a page description in XML (data from databases, other websites, user session, etc) and turn it to HTML as the last step. Other folk in my area are doing much more with it.

LarryC: Sasha, I'll take your advice and leap in! Re: JSP as XML documents, yes that is the plan, we are still working out the details of the mapping. the JSP1.1 spec should be updated in public draft within the next couple of weeks.

LarryC: Thanks MojoJojo ... that's useful info.

MarkR: Re. the DOM: This is a pretty complicated API. We've sometimes thought that it might be worth doing a highly simplified parse-tree-based API for XML. Something vaguely like the DOM, but *much* lighter in weight and much easier to understand and use. I'd be interested to hear whether this is something that folks would like to see.

MDR-edort: The question queue is dry again. Any more questions?


Hank Oxford: Re: what we're using... My comments pretty much mirror MojoJojo's. We're primarily using SAX 1.0 here. As Mojo said, we can more efficiently build our own structures with SAX than use the DOM ones.

Anna: Answer to Larry's question on who is using what? DOM 1.0 right now. Plan to use SAX 1.0 for some larger files Using XSL-patterns to query the DOM. Question: Are there any plans for supporting querying a DOM using XSL-patterns?

LarryC: That would be XQL.


Hank Oxford: Are you tracking the MDSAX/Coins work at all? What about serialization using XML in general?

kuni: How about XLink and XPointer? Have you guys begun looking at that yet?

LarryC: We are looking at both XLink and Xpointer and would plan to provide support when they stabilize ... I think Xpointer is more likely to do this before XLink which is more ambitious. What would your application for them be?


MojoJojo: Mark asked about DOM -- or something simpler. Seems to me that with the Java 2 collections, and classes for elements and PIs, it's already almost there. If there were base classes for those (and an interface for elements; I'll need my own base classes too!) then just documenting a set of conventions would suffice ... if there were ways to read and write the XML from such structures. I suspect I'd use that in many places I use DOM. But I'd have to think about it. That wouldn't be a "tree" that can be walked up and down.

MarkR: MDSAX/Coins -- yes, we're tracking this work. Serialization -- It's often hard to discern what people mean by this. If you mean replacing the platform's current serialization mechanism then the answer is no, there's no way we're going to do that. The JFC Project Swing team has been exploring some interesting strategies for archiving graphs of JavaBeans^TM in XML, and an outgrowth of the data-binding project may yield a more general-purpose runtime archiver, but these aren't our top priorities right now.


ricardo: Any suggestions on a easy-to-understand reference manual for the Java programming language?

MarkR: MojoJojo -- thanks for the input on DOM. I agree that leveraging the collections framework would be a good thing.

MDR-edort: You can find a number of links to good basic Java material on the JDC.

MDR-edort: We're down to the last 10 minutes of the session. If you've got any questions you'd like Mark or Larry to answer, please submit them soon.


Sasha Nakhimovsk: Re: XSLT and JSP: there is a significant overlap between them. I think XSLT spec says that implementaions don't have to support extensions into any particular language, but they may. If Sun provides an XSLT implementation that supports loading and using JavaBeans wouldn't that be very close to JSP?

LarryC: Sasha, Eduardo and I (we authored the JSP spec) have been working with the XSL developers to understand what the relationship is between the two. We don't have an answer yet, but we do see a synergy. One important thing to note is that although they do very similar things the programming models are very different; with JSP it is very much centered around a model where streams of characters are input/output effected by an integrated (imperative) scripting language engine, XSLT on the other hand is a declarative, transformation model, based on pattern matching on an XML input document and generating a result tree. these models are sufficiently different that the models themselves become significant in the decision of which mechanism to choose to solve a particular problem! PHEW!

MDR-edort: With that, we'll end what has been an excellent session. Thanks for your participation.


MojoJojo: Re XSL/T vs JSP/ASP ... there's a key difference, a style sheet gets applied to a document (XML + XSL --> HTML) where the JSP/ASP is just executed directly (JSP/ASP -->HTML). That is, XSL can be applied to many pages; JSP to just one. Of course, sometimes I use XSL to craft a custom page. But more typically I use some other component to craft a custom input to a standard XSL stylesheet. While with JSP/ASP, the "pagequot; itself is that component. (This ties into what Larry just wrote ...) So when I design a section of a site, the interesting question is how the overall application works. The workflow inside the site, if you will.

LarryC: Mojojojo: Exactly!!! ... I think they complement/co-exist!

MDR-edort: Now it's definitely the end of the session. Thanks again.

MDR-edort: Last moderator (me) signing off. The forum is now unmoderated


Forum closed at Thu Aug 5 15:25:11 1999

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