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I am very supportive of John's proposal for a pull-based API. *If*, from
the outset, it belongs in the public domain.
As others have noted, there are already several examples in use today but
none, as far as I know, are in the public domain. I think this is an
opportunity for XML-DEV to get together like they did for SAX and design an
API that becomes de-facto if not a standard.
We have been planning to offer a pull-based API to our C++ XML Toolkit and I
would be pleased if this could be based on a common standard instead of yet
another proprietary interface. We will certainly contribute to a public
project.
Regards
~Rob
--
Rob Lugt
ElCel Technology
http://www.elcel.com
----- Original Message -----
From: "John Cowan" <jcowan@reutershealth.com>
To: <xml-dev@lists.xml.org>
Sent: Monday, December 17, 2001 10:11 PM
Subject: [xml-dev] DESIGN PROPOSAL: Java XMLIterator
> We currently have two base-level APIs for XML processing in
> the Java world: DOM and its variant JDOM, which build in-memory
> trees, and SAX, which pushes a stream of events to application
> event-handling methods.
>
> This is a first design for XMLIterator, a third base-level API
> which allows an application to pull content from XML. This
> avoids the memory demand and navigation issues of DOM, and
> is a more straightforward programming model than SAX, which
> requires magic data connections between the event handlers in
> order to maintain application state. XMLIterator extends
> the familiar Iterator interface, so it models an XML document
> as a linear collection of partially specified nodes.
>
> I am asking this list to help me refine the design of XMLIterator,
> and then build two implementations: SAXAdapter and DOMAdapter,
> for layering over SAX and DOM parsers respectively.
>
>
> // This is version 0.1 of XMLIterator
> // It supports SAX2 events only, and does not handle
> // prefix-mapping events (because I haven't figured out
> // what the Right Thing is). Stuff provided only by
> // DOM should be factored in too.
>
> package org.ccil.cowan.iter;
> public interface XMLIterator
> extends java.util.Iterator {
>
> // Processing model: Iteration starts with the
> // ELEMENT node of the document element, and on successive
> // calls to next(), proceeds through the document,
> // returning ELEMENT, ATTRIBUTE, SKIPPED_ENTITY,
> // END_ELEMENT, and PI nodes in document order
> // (except that ATTRIBUTE nodes appear just after
> // their owner ELEMENT node in arbitrary order),
> // followed by the END node.
>
> // hasNext is inherited from Iterator, and returns true
> // if the current node is not an END node
>
> // next is inherited from Iterator, and returns an XMLNode
> // object, which may be self; XMLIterators are encouraged
> // to play the role of both the iterator and the component
> // object, to avoid excessive object creation (as such,
> // the XMLNode is considered invalid after the following
> // invocation of next).
>
> // remove is inherited from Iterator, and throws an
> // exception, since XMLIterator is read-only
>
> // Node types: legal return values of XMLNode.getType method
> public static int END = 0;
> public static int ELEMENT = 1;
> public static int ATTRIBUTE = 2;
> public static int SKIPPED_ENTITY = 3;
> public static int END_ELEMENT = 4;
> public static int PI = 5;
>
> // Attribute types: legal return values of getAttributeType method
> public static int CDATA = 0;
> public static int ID = 1;
> public static int IDREF = 2;
> public static int IDREFS = 3;
> public static int NMTOKEN = 4; // also used for enumerations
> public static int NMTOKENS = 5;
> public static int ENTITY = 6;
> public static int ENTITIES = 7;
> public static int NOTATION = 8;
>
>
> // Convenience methods
>
> // If the current node is an ELEMENT or ATTRIBUTE node,
> // skip all nodes to the next non-ATTRIBUTE node.
> // This allows us to ignore attributes if we do not care
> // about any more.
> public void skipAttributes();
>
> // Skip all nodes up to and including the END_ELEMENT node
> // corresponding to the most recently seen ELEMENT node
> // (the current node, if that is an ELEMENT node)
> public void skipElement();
>
> }
>
>
> package org.ccil.cowan.iter;
> public interface XMLNode {
>
> // Read-only properties of the current node
> // Lazy implementation is encouraged
>
> // Returns the current Locator object
> public org.xml.sax.Locator getLocator();
>
> // Returns a node type code
> public int getType();
>
> // If the current node is an ATTRIBUTE node, return
> // an attribute type code
> public int getAttributeType();
>
> // If the current node is an ELEMENT or ATTRIBUTE node,
> // and namespace URI information is available,
> // return it
> public string getNSURI();
>
> // If the current node is an ELEMENT or ATTRIBUTE node,
> // and QName information is available, return it
> public string getQName();
>
> // If the current node is an ELEMENT or ATTRIBUTE node, and
> // local name information is available, return it;
> // if the current node is a PI node, return the target;
> // if the current node is a SKIPPED_ENTITY node,
> // return the entity name
> public string getLocalName();
>
> // If the current node is an ELEMENT node,
> // return an Attributes object containing the attributes
> public org.xml.sax.Attributes getAttributes();
>
> // If the current node is an ELEMENT node,
> // return all text content up to the next tag;
> // if the current node is an ATTRIBUTE node,
> // return the normalized attribute value;
> // if the current node is an END_ELEMENT node,
> // return all text content up to the next tag;
> // if the current node is a PI node,
> // return the content of the PI
> public string getValue();
>
> // If the current node is an ELEMENT or END_ELEMENT node,
> // return true if the value property consists of ignorable whitespace
> public bool isIgnorableWhitespace();
>
> }
>
>
> --
> Not to perambulate || John Cowan <jcowan@reutershealth.com>
> the corridors || http://www.reutershealth.com
> during the hours of repose || http://www.ccil.org/~cowan
> in the boots of ascension. \\ Sign in Austrian ski-resort hotel
>
>
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