YAXPAPI (Yet Another XML Parser API)- an XDEV proposal

[Don Park]

Tim and Peter,

From: Tim Bray <tbray at textuality.com>
>It should come in event-stream flavor and tree flavor.
>
>Minimal event stream API:
>
>1. Doctype, returns: root type, external subset system/public idents
>2. Element start, returns: type, element name-value pairs, whether it's
empty
>3. Text
>4. End Element, returns: type
>
>Minimal tree API:
>
>1. Document, with methods: root type, system ID, public ID, root element
>2. Element, with methods: parent, children, attributeValueByName,
allAttributes
>3. Attribute, with methods: name, value
>4. Text (presumably hiding lazy evaluation)


IMHO, it would be major mistake to combine XML parser client API and service
provider API.  I would much rather see something like Swing's TreeModel
interface used as XML parser service provider API with opaque objects.

public interface XmlTreeModel {
    public Object getRoot ();
    public Object getParent (Object child);
    ...
}

public interface XmlEventModel {
    public String getElementName (Object event);
    ...
}

public interface XmlEventProducer {
    public void addConsumer (XmlEventConsumer c);
    public void removeConsumer (XmlEventConsumer c);
    ...
}

public interface XmlEventConsumer {
    public void elementStarted (XmlElementEvent evt);
    public void elementEnd ed (XmlElementEvent evt);
    ...
}

XmlEvent is part of the client API which is mostly convenience class
framework:

public class XmlEvent extends EventObject {
    protected XmlEventModel    model;
    protected Object                    object;
    ...
}

public class XmlElementEvent extends XmlEvent {
    public String getElementName () {
        return model.getElementName(object);
    ...
}

>I acknowledge this is grossly insufficient for basing an editor on. You
want
>that, use the DOM.  Only a few choices have design implications:


I think editing should be supported with another layer of interfaces so that
basic interface can remain simpler.

public interface MutableXmlTreeModel {
    public Object newElement (String name, ...);
    public void addAttribute(Object elem, String name, String value);
    ...
}

XML parser service provider API is mostly just interfaces and deals with
opaque objects returned by XML parser implementations.  XML parser client
API consists of DOM classes uses opaque objects to drive parsers
implementations (see XmlElementEvent above).


Don Park




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