Document Object Model Load and Save

07 April 2004

# 1. Document Object Model Load and Save

Editors:
  Johnny Stenback, Netscape
  Andy Heninger, IBM (until March 2001)

## Table of contents

This section defines a set of interfaces for loading and saving document objects as defined in [DOM Level 2 Core] or newer. The functionality specified in this section (the Load and Save functionality) is sufficient to allow software developers and Web script authors to load and save XML content inside conforming products. The DOM Load and Save API also allows filtering of XML content using only DOM API calls; access and manipulation of the `Document` is defined in [DOM Level 2 Core] or newer.

The proposal for loading is influenced by the Java APIs for XML Processing [JAXP] and by SAX2 [SAX].

## 1.1 Overview of the Interfaces

The interfaces involved with the loading and saving of XML documents are:

- `DOMImplementationLS` -- An extended `DOMImplementation` interface that provides the factory methods for creating the objects required for loading and saving.
- `LSParser` -- An interface for parsing data into DOM documents.
- `LSInput` -- Encapsulates information about the data to be loaded.
- `LSResourceResolver` -- Provides a way for applications to redirect references to external resources when parsing.
- `LSParserFilter` -- Provides the ability to examine and optionally remove nodes as they are being processed while parsing.
- `LSSerializer` -- An interface for serializing DOM documents or nodes.
- `LSOutput` -- Encapsulates information about the destination for the data to be output.
- `LSSerializerFilter` -- Provides the ability to examine and filter DOM nodes as they are being processed for the serialization.

## 1.2 Basic Types

To ensure interoperability, this specification specifies the following basic types used in various DOM modules. Even though the DOM uses the basic types in the interfaces, bindings may use different types and normative bindings are only given for Java and ECMAScript in this specification.

### 1.2.1 The `LSInputStream` Type

This type is used to represent a sequence of input bytes.

Type Definition LSInputStream

  A `LSInputStream` represents a reference to a byte stream source of an XML input.

  IDL Definition

        typedef Object LSInputStream;

Note: For Java, `LSInputStream` is bound to the `java.io.InputStream` type. For ECMAScript, `LSInputStream` is bound to `Object`.

### 1.2.2 The `LSOutputStream` Type

This type is used to represent a sequence of output bytes.

Type Definition LSOutputStream

  A `LSOutputStream` represents a byte stream destination for the XML output.

  IDL Definition

        typedef Object LSOutputStream;

Note: For Java, `LSOutputStream` is bound to the `java.io.OutputStream` type. For ECMAScript, `LSOutputStream` is bound to `Object`.

### 1.2.3 The `LSReader` Type

This type is used to represent a sequence of input characters in 16-bit units. The encoding used for the characters is UTF-16, as defined in [Unicode] and in [ISO/IEC 10646]).

Type Definition LSReader

  A `LSReader` represents a character stream for the XML input.

  IDL Definition

        typedef Object LSReader;

Note: For Java, `LSReader` is bound to the `java.io.Reader` type. For ECMAScript, `LSReader` is not bound, and therefore has no recommended meaning in ECMAScript.

### 1.2.4 The `LSWriter` Type

This type is used to represent a sequence of output characters in 16-bit units. The encoding used for the characters is UTF-16, as defined in [Unicode] and in [ISO/IEC 10646]).

Type Definition LSWriter

  A `LSWriter` represents a character stream for the XML output.

  IDL Definition

        typedef Object LSWriter;

Note: For Java, `LSWriter` is bound to the `java.io.Writer` type. For ECMAScript, `LSWriter` is not bound, and therefore has no recommended meaning in ECMAScript.

## 1.3 Fundamental Interfaces

The interfaces within this section are considered fundamental, and must be fully implemented by all conforming implementations of the DOM Load and Save module.

A DOM application may use the `hasFeature(feature, version)` method of the `DOMImplementation` interface with parameter values `"LS"` (or `"LS-Async"`) and `"3.0"` (respectively) to determine whether or not these interfaces are supported by the implementation. In order to fully support them, an implementation must also support the "Core" feature defined in [DOM Level 2 Core].

A DOM application may use the `hasFeature(feature, version)` method of the `DOMImplementation` interface with parameter values `"LS-Async"` and `"3.0"` (respectively) to determine whether or not the asynchronous mode is supported by the implementation. In order to fully support the asynchronous mode, an implementation must also support the `"LS"` feature defined in this section.

For additional information about conformance, please see the DOM Level 3 Core specification [DOM Level 3 Core].

Exception LSException

  Parser or write operations may throw an `LSException` if the processing is stopped. The processing can be stopped due to a `DOMError` with a severity of `DOMError.SEVERITY_FATAL_ERROR` or a non recovered `DOMError.SEVERITY_ERROR`, or if `DOMErrorHandler.handleError()` returned `false`.

  Note: As suggested in the definition of the constants in the `DOMError` interface, a DOM implementation may choose to continue after a fatal error, but the resulting DOM tree is then implementation dependent.

  IDL Definition

        exception LSException {
          unsigned short   code;
        };
        // LSExceptionCode
        const unsigned short      PARSE_ERR                      = 81;
        const unsigned short      SERIALIZE_ERR                  = 82;

  Definition group LSExceptionCode

    An integer indicating the type of error generated.

    Defined Constants
      `PARSE_ERR`
        If an attempt was made to load a document, or an XML Fragment, using `LSParser` and the processing has been stopped.
      `SERIALIZE_ERR`
        If an attempt was made to serialize a `Node` using `LSSerializer` and the processing has been stopped.
Interface DOMImplementationLS

  `DOMImplementationLS` contains the factory methods for creating Load and Save objects.

  The expectation is that an instance of the `DOMImplementationLS` interface can be obtained by using binding-specific casting methods on an instance of the `DOMImplementation` interface or, if the `Document` supports the feature `"Core"` version `"3.0"` defined in [DOM Level 3 Core], by using the method `DOMImplementation.getFeature` with parameter values `"LS"` (or `"LS-Async"`) and `"3.0"` (respectively).

  IDL Definition

        interface DOMImplementationLS {

          // DOMImplementationLSMode
          const unsigned short      MODE_SYNCHRONOUS               = 1;
          const unsigned short      MODE_ASYNCHRONOUS              = 2;

          LSParser           createLSParser(in unsigned short mode,
                                            in DOMString schemaType)
                                                raises(DOMException);
          LSSerializer       createLSSerializer();
          LSInput            createLSInput();
          LSOutput           createLSOutput();
        };

  Definition group DOMImplementationLSMode

    Integer parser mode constants.

    Defined Constants
      `MODE_ASYNCHRONOUS`
        Create an asynchronous `LSParser`.
      `MODE_SYNCHRONOUS`
        Create a synchronous `LSParser`.
  Methods
    `createLSInput`
      Create a new empty input source object where `LSInput.characterStream`, `LSInput.byteStream`, `LSInput.stringData` `LSInput.systemId`, `LSInput.publicId`, `LSInput.baseURI`, and `LSInput.encoding` are null, and `LSInput.certifiedText` is false.
      Return Value

      `LSInput` | The newly created input object.

      No Parameters
      No Exceptions
    `createLSOutput`
      Create a new empty output destination object where `LSOutput.characterStream`, `LSOutput.byteStream`, `LSOutput.systemId`, `LSOutput.encoding` are null.
      Return Value

      `LSOutput` | The newly created output object.

      No Parameters
      No Exceptions
    `createLSParser`
      Create a new `LSParser`. The newly constructed parser may then be configured by means of its `DOMConfiguration` object, and used to parse documents by means of its `parse` method.
      Parameters
      `mode` of type `unsigned short`
        The `mode` argument is either `MODE_SYNCHRONOUS` or `MODE_ASYNCHRONOUS`, if `mode` is `MODE_SYNCHRONOUS` then the `LSParser` that is created will operate in synchronous mode, if it's `MODE_ASYNCHRONOUS` then the `LSParser` that is created will operate in asynchronous mode.
      `schemaType` of type `DOMString`
        An absolute URI representing the type of the schema language used during the load of a `Document` using the newly created `LSParser`. Note that no lexical checking is done on the absolute URI. In order to create a `LSParser` for any kind of schema types (i.e. the LSParser will be free to use any schema found), use the value `null`.

        Note: For W3C XML Schema [XML Schema Part 1], applications must use the value `"http://www.w3.org/2001/XMLSchema"`. For XML DTD [XML 1.0], applications must use the value `"http://www.w3.org/TR/REC-xml"`. Other Schema languages are outside the scope of the W3C and therefore should recommend an absolute URI in order to use this method.

      Return Value

      `LSParser` | The newly created `LSParser` object. This `LSParser` is either synchronous or asynchronous depending on the value of the `mode` argument. Note: By default, the newly created `LSParser` does not contain a `DOMErrorHandler`, i.e. the value of the "error-handler" configuration parameter is `null`. However, implementations may provide a default error handler at creation time. In that case, the initial value of the `"error-handler"` configuration parameter on the new `LSParser` object contains a reference to the default error handler.

      Exceptions

      `DOMException` | NOT_SUPPORTED_ERR: Raised if the requested mode or schema type is not supported.

    `createLSSerializer`
      Create a new `LSSerializer` object.
      Return Value

      `LSSerializer` | The newly created `LSSerializer` object. Note: By default, the newly created `LSSerializer` has no `DOMErrorHandler`, i.e. the value of the `"error-handler"` configuration parameter is `null`. However, implementations may provide a default error handler at creation time. In that case, the initial value of the `"error-handler"` configuration parameter on the new `LSSerializer` object contains a reference to the default error handler.

      No Parameters
      No Exceptions
Interface LSParser

  An interface to an object that is able to build, or augment, a DOM tree from various input sources.

  `LSParser` provides an API for parsing XML and building the corresponding DOM document structure. A `LSParser` instance can be obtained by invoking the `DOMImplementationLS.createLSParser()` method.

  As specified in [DOM Level 3 Core], when a document is first made available via the LSParser:

  - there will never be two adjacent nodes of type NODE_TEXT, and there will never be empty text nodes.
  - it is expected that the `value` and `nodeValue` attributes of an `Attr` node initially return the XML 1.0 normalized value. However, if the parameters "validate-if-schema" and "datatype-normalization" are set to `true`, depending on the attribute normalization used, the attribute values may differ from the ones obtained by the XML 1.0 attribute normalization. If the parameters "datatype-normalization" is set to `false`, the XML 1.0 attribute normalization is guaranteed to occur, and if the attributes list does not contain namespace declarations, the `attributes` attribute on `Element` node represents the property [attributes] defined in [XML Information Set].

  Asynchronous `LSParser` objects are expected to also implement the `events::EventTarget` interface so that event listeners can be registered on asynchronous `LSParser` objects.

  Events supported by asynchronous `LSParser` objects are:

  load
    The `LSParser` finishes to load the document. See also the definition of the `LSLoadEvent` interface.
  progress
    The `LSParser` signals progress as data is parsed.
    This specification does not attempt to define exactly when progress events should be dispatched. That is intentionally left as implementation-dependent. Here is one example of how an application might dispatch progress events: Once the parser starts receiving data, a progress event is dispatched to indicate that the parsing starts. From there on, a progress event is dispatched for every 4096 bytes of data that is received and processed. This is only one example, though, and implementations can choose to dispatch progress events at any time while parsing, or not dispatch them at all.
    See also the definition of the `LSProgressEvent` interface.

  Note: All events defined in this specification use the namespace URI `"http://www.w3.org/2002/DOMLS"`.

  While parsing an input source, errors are reported to the application through the error handler (`LSParser.domConfig`'s "error-handler" parameter). This specification does in no way try to define all possible errors that can occur while parsing XML, or any other markup, but some common error cases are defined. The types (`DOMError.type`) of errors and warnings defined by this specification are:

  `"check-character-normalization-failure" [error]`
    Raised if the parameter "check-character-normalization" is set to true and a string is encountered that fails normalization checking.
  `"doctype-not-allowed" [fatal]`
    Raised if the configuration parameter "disallow-doctype" is set to `true` and a doctype is encountered.
  `"no-input-specified" [fatal]`
    Raised when loading a document and no input is specified in the `LSInput` object.
  `"pi-base-uri-not-preserved" [warning]`
    Raised if a processing instruction is encountered in a location where the base URI of the processing instruction can not be preserved.
    One example of a case where this warning will be raised is if the configuration parameter "entities" is set to `false` and the following XML file is parsed:

        <!DOCTYPE root [
        <!ENTITY e SYSTEM 'subdir/myentity.ent'
        ]>

        <root>
        &e;
        </root>

    And `subdir/myentity.ent` contains:

        <one>
          <two/>
        </one>
        <?pi 3.14159?>
        <more/>

  `"unbound-prefix-in-entity" [warning]`
    An implementation dependent warning that may be raised if the configuration parameter "namespaces" is set to `true` and an unbound namespace prefix is encountered in an entity's replacement text. Raising this warning is not enforced since some existing parsers may not recognize unbound namespace prefixes in the replacement text of entities.
  `"unknown-character-denormalization" [fatal]`
    Raised if the configuration parameter "ignore-unknown-character-denormalizations" is set to `false` and a character is encountered for which the processor cannot determine the normalization properties.
  `"unsupported-encoding" [fatal]`
    Raised if an unsupported encoding is encountered.
  `"unsupported-media-type" [fatal]`
    Raised if the configuration parameter "supported-media-types-only" is set to `true` and an unsupported media type is encountered.

  In addition to raising the defined errors and warnings, implementations are expected to raise implementation specific errors and warnings for any other error and warning cases such as IO errors (file not found, permission denied,...), XML well-formedness errors, and so on.

  IDL Definition

        interface LSParser {
          readonly attribute DOMConfiguration domConfig;
                   attribute LSParserFilter  filter;
          readonly attribute boolean         async;
          readonly attribute boolean         busy;
          Document           parse(in LSInput input)
                                                raises(DOMException,
                                                       LSException);
          Document           parseURI(in DOMString uri)
                                                raises(DOMException,
                                                       LSException);

          // ACTION_TYPES
          const unsigned short      ACTION_APPEND_AS_CHILDREN      = 1;
          const unsigned short      ACTION_REPLACE_CHILDREN        = 2;
          const unsigned short      ACTION_INSERT_BEFORE           = 3;
          const unsigned short      ACTION_INSERT_AFTER            = 4;
          const unsigned short      ACTION_REPLACE                 = 5;

          Node               parseWithContext(in LSInput input,
                                              in Node contextArg,
                                              in unsigned short action)
                                                raises(DOMException,
                                                       LSException);
          void               abort();
        };

  Definition group ACTION_TYPES

    A set of possible actions for the `parseWithContext` method.

    Defined Constants
      `ACTION_APPEND_AS_CHILDREN`
        Append the result of the parse operation as children of the context node. For this action to work, the context node must be an `Element` or a `DocumentFragment`.
      `ACTION_INSERT_AFTER`
        Insert the result of the parse operation as the immediately following sibling of the context node. For this action to work the context node's parent must be an `Element` or a `DocumentFragment`.
      `ACTION_INSERT_BEFORE`
        Insert the result of the parse operation as the immediately preceding sibling of the context node. For this action to work the context node's parent must be an `Element` or a `DocumentFragment`.
      `ACTION_REPLACE`
        Replace the context node with the result of the parse operation. For this action to work, the context node must have a parent, and the parent must be an `Element` or a `DocumentFragment`.
      `ACTION_REPLACE_CHILDREN`
        Replace all the children of the context node with the result of the parse operation. For this action to work, the context node must be an `Element`, a `Document`, or a `DocumentFragment`.
  Attributes
    `async` of type `boolean`, readonly
      `true` if the `LSParser` is asynchronous, `false` if it is synchronous.
    `busy` of type `boolean`, readonly
      `true` if the `LSParser` is currently busy loading a document, otherwise `false`.
    `domConfig` of type `DOMConfiguration`, readonly
      The `DOMConfiguration` object used when parsing an input source. This `DOMConfiguration` is specific to the parse operation. No parameter values from this `DOMConfiguration` object are passed automatically to the `DOMConfiguration` object on the `Document` that is created, or used, by the parse operation. The DOM application is responsible for passing any needed parameter values from this `DOMConfiguration` object to the `DOMConfiguration` object referenced by the `Document` object.
      In addition to the parameters recognized in on the DOMConfiguration interface defined in [DOM Level 3 Core], the `DOMConfiguration` objects for `LSParser` add or modify the following parameters:
      `"charset-overrides-xml-encoding"`
        `true`
          [optional] (default)
          If a higher level protocol such as HTTP [IETF RFC 2616] provides an indication of the character encoding of the input stream being processed, that will override any encoding specified in the XML declaration or the Text declaration (see also section 4.3.3, "Character Encoding in Entities", in [XML 1.0]). Explicitly setting an encoding in the `LSInput` overrides any encoding from the protocol.
        `false`
          [required]
          The parser ignores any character set encoding information from higher-level protocols.
      `"disallow-doctype"`
        `true`
          [optional]
          Throw a fatal "doctype-not-allowed" error if a doctype node is found while parsing the document. This is useful when dealing with things like SOAP envelopes where doctype nodes are not allowed.
        `false`
          [required] (default)
          Allow doctype nodes in the document.
      `"ignore-unknown-character-denormalizations"`
        `true`
          [required] (default)
          If, while verifying full normalization when [XML 1.1] is supported, a processor encounters characters for which it cannot determine the normalization properties, then the processor will ignore any possible denormalizations caused by these characters.
          This parameter is ignored for [XML 1.0].
        `false`
          [optional]
          Report an fatal "unknown-character-denormalization" error if a character is encountered for which the processor cannot determine the normalization properties.
      `"infoset"`
        See the definition of `DOMConfiguration` for a description of this parameter. Unlike in [DOM Level 3 Core], this parameter will default to `true` for `LSParser`.
      `"namespaces"`
        `true`
          [required] (default)
          Perform the namespace processing as defined in [XML Namespaces] and [XML Namespaces 1.1].
        `false`
          [optional]
          Do not perform the namespace processing.
      `"resource-resolver"`
        [required]
        A reference to a `LSResourceResolver` object, or null. If the value of this parameter is not null when an external resource (such as an external XML entity or an XML schema location) is encountered, the implementation will request that the `LSResourceResolver` referenced in this parameter resolves the resource.
      `"supported-media-types-only"`
        `true`
          [optional]
          Check that the media type of the parsed resource is a supported media type. If an unsupported media type is encountered, a fatal error of type "unsupported-media-type" will be raised. The media types defined in [IETF RFC 3023] must always be accepted.
        `false`
          [required] (default)
          Accept any media type.
      `"validate"`
        See the definition of `DOMConfiguration` for a description of this parameter. Unlike in [DOM Level 3 Core], the processing of the internal subset is always accomplished, even if this parameter is set to `false`.
      `"validate-if-schema"`
        See the definition of `DOMConfiguration` for a description of this parameter. Unlike in [DOM Level 3 Core], the processing of the internal subset is always accomplished, even if this parameter is set to `false`.
      `"well-formed"`
        See the definition of `DOMConfiguration` for a description of this parameter. Unlike in [DOM Level 3 Core], this parameter cannot be set to `false`.
    `filter` of type `LSParserFilter`
      When a filter is provided, the implementation will call out to the filter as it is constructing the DOM tree structure. The filter can choose to remove elements from the document being constructed, or to terminate the parsing early.
      The filter is invoked after the operations requested by the `DOMConfiguration` parameters have been applied. For example, if "validate" is set to `true`, the validation is done before invoking the filter.
  Methods
    `abort`
      Abort the loading of the document that is currently being loaded by the `LSParser`. If the `LSParser` is currently not busy, a call to this method does nothing.
      No Parameters
      No Return Value
      No Exceptions
    `parse`
      Parse an XML document from a resource identified by a `LSInput`.
      Parameters
      `input` of type `LSInput`
        The `LSInput` from which the source of the document is to be read.
      Return Value

      `Document` | If the `LSParser` is a synchronous `LSParser`, the newly created and populated `Document` is returned. If the `LSParser` is asynchronous, `null` is returned since the document object may not yet be constructed when this method returns.

      Exceptions

      `DOMException` | INVALID_STATE_ERR: Raised if the `LSParser`'s `LSParser.busy` attribute is `true`.
      `LSException` | PARSE_ERR: Raised if the `LSParser` was unable to load the XML document. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

    `parseURI`
      Parse an XML document from a location identified by a URI reference [IETF RFC 2396]. If the URI contains a fragment identifier (see section 4.1 in [IETF RFC 2396]), the behavior is not defined by this specification, future versions of this specification may define the behavior.
      Parameters
      `uri` of type `DOMString`
        The location of the XML document to be read.
      Return Value

      `Document` | If the `LSParser` is a synchronous `LSParser`, the newly created and populated `Document` is returned, or `null` if an error occured. If the `LSParser` is asynchronous, `null` is returned since the document object may not yet be constructed when this method returns.

      Exceptions

      `DOMException` | INVALID_STATE_ERR: Raised if the `LSParser.busy` attribute is `true`.
      `LSException` | PARSE_ERR: Raised if the `LSParser` was unable to load the XML document. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

    `parseWithContext`
      Parse an XML fragment from a resource identified by a `LSInput` and insert the content into an existing document at the position specified with the `context` and `action` arguments. When parsing the input stream, the context node (or its parent, depending on where the result will be inserted) is used for resolving unbound namespace prefixes. The context node's `ownerDocument` node (or the node itself if the node of type `DOCUMENT_NODE`) is used to resolve default attributes and entity references.
      As the new data is inserted into the document, at least one mutation event is fired per new immediate child or sibling of the context node.
      If the context node is a `Document` node and the action is `ACTION_REPLACE_CHILDREN`, then the document that is passed as the context node will be changed such that its `xmlEncoding`, `documentURI`, `xmlVersion`, `inputEncoding`, `xmlStandalone`, and all other such attributes are set to what they would be set to if the input source was parsed using `LSParser.parse()`.
      This method is always synchronous, even if the `LSParser` is asynchronous (`LSParser.async` is `true`).
      If an error occurs while parsing, the caller is notified through the `ErrorHandler` instance associated with the "error-handler" parameter of the `DOMConfiguration`.
      When calling `parseWithContext`, the values of the following configuration parameters will be ignored and their default values will always be used instead: "validate", "validate-if-schema", and "element-content-whitespace". Other parameters will be treated normally, and the parser is expected to call the `LSParserFilter` just as if a whole document was parsed.
      Parameters
      `input` of type `LSInput`
        The `LSInput` from which the source document is to be read. The source document must be an XML fragment, i.e. anything except a complete XML document (except in the case where the context node of type `DOCUMENT_NODE`, and the action is `ACTION_REPLACE_CHILDREN`), a DOCTYPE (internal subset), entity declaration(s), notation declaration(s), or XML or text declaration(s).
      `contextArg` of type `Node`
        The node that is used as the context for the data that is being parsed. This node must be a `Document` node, a `DocumentFragment` node, or a node of a type that is allowed as a child of an `Element` node, e.g. it cannot be an `Attribute` node.
      `action` of type `unsigned short`
        This parameter describes which action should be taken between the new set of nodes being inserted and the existing children of the context node. The set of possible actions is defined in `ACTION_TYPES` above.
      Return Value

      `Node` | Return the node that is the result of the parse operation. If the result is more than one top-level node, the first one is returned.

      Exceptions

      `DOMException` | HIERARCHY_REQUEST_ERR: Raised if the content cannot replace, be inserted before, after, or as a child of the context node (see also `Node.insertBefore` or `Node.replaceChild` in [DOM Level 3 Core]). NOT_SUPPORTED_ERR: Raised if the `LSParser` doesn't support this method, or if the context node is of type `Document` and the DOM implementation doesn't support the replacement of the `DocumentType` child or `Element` child. NO_MODIFICATION_ALLOWED_ERR: Raised if the context node is a read only node and the content is being appended to its child list, or if the parent node of the context node is read only node and the content is being inserted in its child list. INVALID_STATE_ERR: Raised if the `LSParser.busy` attribute is `true`.
      `LSException` | PARSE_ERR: Raised if the `LSParser` was unable to load the XML fragment. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

Interface LSInput

  This interface represents an input source for data.

  This interface allows an application to encapsulate information about an input source in a single object, which may include a public identifier, a system identifier, a byte stream (possibly with a specified encoding), a base URI, and/or a character stream.

  The exact definitions of a byte stream and a character stream are binding dependent.

  The application is expected to provide objects that implement this interface whenever such objects are needed. The application can either provide its own objects that implement this interface, or it can use the generic factory method `DOMImplementationLS.createLSInput()` to create objects that implement this interface.

  The `LSParser` will use the `LSInput` object to determine how to read data. The `LSParser` will look at the different inputs specified in the `LSInput` in the following order to know which one to read from, the first one that is not null and not an empty string will be used:

  1. `LSInput.characterStream`
  2. `LSInput.byteStream`
  3. `LSInput.stringData`
  4. `LSInput.systemId`
  5. `LSInput.publicId`

  If all inputs are null, the `LSParser` will report a `DOMError` with its `DOMError.type` set to `"no-input-specified"` and its `DOMError.severity` set to `DOMError.SEVERITY_FATAL_ERROR`.

  `LSInput` objects belong to the application. The DOM implementation will never modify them (though it may make copies and modify the copies, if necessary).

  IDL Definition

        interface LSInput {
          // Depending on the language binding in use,
          // this attribute may not be available.
                   attribute LSReader        characterStream;
                   attribute LSInputStream   byteStream;
                   attribute DOMString       stringData;
                   attribute DOMString       systemId;
                   attribute DOMString       publicId;
                   attribute DOMString       baseURI;
                   attribute DOMString       encoding;
                   attribute boolean         certifiedText;
        };

  Attributes
    `baseURI` of type `DOMString`
      The base URI to be used (see section 5.1.4 in [IETF RFC 2396]) for resolving a relative `systemId` to an absolute URI.
      If, when used, the base URI is itself a relative URI, an empty string, or null, the behavior is implementation dependent.
    `byteStream` of type `LSInputStream`
      An attribute of a language and binding dependent type that represents a stream of bytes.
      If the application knows the character encoding of the byte stream, it should set the encoding attribute. Setting the encoding in this way will override any encoding specified in an XML declaration in the data.
    `certifiedText` of type `boolean`
      If set to true, assume that the input is certified (see section 2.13 in [XML 1.1]) when parsing [XML 1.1].
    `characterStream` of type `LSReader`
    Depending on the language binding in use, this attribute may not be available.
      An attribute of a language and binding dependent type that represents a stream of 16-bit units. The application must encode the stream using UTF-16 (defined in [Unicode] and in [ISO/IEC 10646]). It is not a requirement to have an XML declaration when using character streams. If an XML declaration is present, the value of the encoding attribute will be ignored.
    `encoding` of type `DOMString`
      The character encoding, if known. The encoding must be a string acceptable for an XML encoding declaration ([XML 1.0] section 4.3.3 "Character Encoding in Entities").
      This attribute has no effect when the application provides a character stream or string data. For other sources of input, an encoding specified by means of this attribute will override any encoding specified in the XML declaration or the Text declaration, or an encoding obtained from a higher level protocol, such as HTTP [IETF RFC 2616].
    `publicId` of type `DOMString`
      The public identifier for this input source. This may be mapped to an input source using an implementation dependent mechanism (such as catalogues or other mappings). The public identifier, if specified, may also be reported as part of the location information when errors are reported.
    `stringData` of type `DOMString`
      String data to parse. If provided, this will always be treated as a sequence of 16-bit units (UTF-16 encoded characters). It is not a requirement to have an XML declaration when using `stringData`. If an XML declaration is present, the value of the encoding attribute will be ignored.
    `systemId` of type `DOMString`
      The system identifier, a URI reference [IETF RFC 2396], for this input source. The system identifier is optional if there is a byte stream, a character stream, or string data. It is still useful to provide one, since the application will use it to resolve any relative URIs and can include it in error messages and warnings. (The LSParser will only attempt to fetch the resource identified by the URI reference if there is no other input available in the input source.)
      If the application knows the character encoding of the object pointed to by the system identifier, it can set the encoding using the `encoding` attribute.
      If the specified system ID is a relative URI reference (see section 5 in [IETF RFC 2396]), the DOM implementation will attempt to resolve the relative URI with the `baseURI` as the base, if that fails, the behavior is implementation dependent.
Interface LSResourceResolver

  `LSResourceResolver` provides a way for applications to redirect references to external resources.

  Applications needing to implement custom handling for external resources can implement this interface and register their implementation by setting the "resource-resolver" parameter of `DOMConfiguration` objects attached to `LSParser` and `LSSerializer`. It can also be register on `DOMConfiguration` objects attached to `Document` if the "LS" feature is supported.

  The `LSParser` will then allow the application to intercept any external entities, including the external DTD subset and external parameter entities, before including them. The top-level document entity is never passed to the `resolveResource` method.

  Many DOM applications will not need to implement this interface, but it will be especially useful for applications that build XML documents from databases or other specialized input sources, or for applications that use URNs.

  Note: `LSResourceResolver` is based on the SAX2 [SAX] `EntityResolver` interface.

  IDL Definition

        interface LSResourceResolver {
          LSInput            resolveResource(in DOMString type,
                                             in DOMString namespaceURI,
                                             in DOMString publicId,
                                             in DOMString systemId,
                                             in DOMString baseURI);
        };

  Methods
    `resolveResource`
      Allow the application to resolve external resources.
      The `LSParser` will call this method before opening any external resource, including the external DTD subset, external entities referenced within the DTD, and external entities referenced within the document element (however, the top-level document entity is not passed to this method). The application may then request that the `LSParser` resolve the external resource itself, that it use an alternative URI, or that it use an entirely different input source.
      Application writers can use this method to redirect external system identifiers to secure and/or local URI, to look up public identifiers in a catalogue, or to read an entity from a database or other input source (including, for example, a dialog box).
      Parameters
      `type` of type `DOMString`
        The type of the resource being resolved. For XML [XML 1.0] resources (i.e. entities), applications must use the value `"http://www.w3.org/TR/REC-xml"`. For XML Schema [XML Schema Part 1], applications must use the value `"http://www.w3.org/2001/XMLSchema"`. Other types of resources are outside the scope of this specification and therefore should recommend an absolute URI in order to use this method.
      `namespaceURI` of type `DOMString`
        The namespace of the resource being resolved, e.g. the target namespace of the XML Schema [XML Schema Part 1] when resolving XML Schema resources.
      `publicId` of type `DOMString`
        The public identifier of the external entity being referenced, or `null` if no public identifier was supplied or if the resource is not an entity.
      `systemId` of type `DOMString`
        The system identifier, a URI reference [IETF RFC 2396], of the external resource being referenced, or `null` if no system identifier was supplied.
      `baseURI` of type `DOMString`
        The absolute base URI of the resource being parsed, or `null` if there is no base URI.
      Return Value

      `LSInput` | A `LSInput` object describing the new input source, or `null` to request that the parser open a regular URI connection to the resource.

      No Exceptions
Interface LSParserFilter

  `LSParserFilter`s provide applications the ability to examine nodes as they are being constructed while parsing. As each node is examined, it may be modified or removed, or the entire parse may be terminated early.

  At the time any of the filter methods are called by the parser, the owner Document and DOMImplementation objects exist and are accessible. The document element is never passed to the `LSParserFilter` methods, i.e. it is not possible to filter out the document element. `Document`, `DocumentType`, `Notation`, `Entity`, and `Attr` nodes are never passed to the `acceptNode` method on the filter. The child nodes of an `EntityReference` node are passed to the filter if the parameter "entities" is set to `false`. Note that, as described by the parameter "entities", unexpanded entity reference nodes are never discarded and are always passed to the filter.

  All validity checking while parsing a document occurs on the source document as it appears on the input stream, not on the DOM document as it is built in memory. With filters, the document in memory may be a subset of the document on the stream, and its validity may have been affected by the filtering.

  All default attributes must be present on elements when the elements are passed to the filter methods. All other default content must be passed to the filter methods.

  DOM applications must not raise exceptions in a filter. The effect of throwing exceptions from a filter is DOM implementation dependent.

  IDL Definition

        interface LSParserFilter {

          // Constants returned by startElement and acceptNode
          const short               FILTER_ACCEPT                  = 1;
          const short               FILTER_REJECT                  = 2;
          const short               FILTER_SKIP                    = 3;
          const short               FILTER_INTERRUPT               = 4;

          unsigned short     startElement(in Element elementArg);
          unsigned short     acceptNode(in Node nodeArg);
          readonly attribute unsigned long   whatToShow;
        };

  Definition group Constants returned by startElement and acceptNode

    Constants returned by `startElement` and `acceptNode`.

    Defined Constants
      `FILTER_ACCEPT`
        Accept the node.
      `FILTER_INTERRUPT`
        Interrupt the normal processing of the document.
      `FILTER_REJECT`
        Reject the node and its children.
      `FILTER_SKIP`
        Skip this single node. The children of this node will still be considered.
  Attributes
    `whatToShow` of type `unsigned long`, readonly
      Tells the `LSParser` what types of nodes to show to the method `LSParserFilter.acceptNode`. If a node is not shown to the filter using this attribute, it is automatically included in the DOM document being built. See `NodeFilter` for definition of the constants. The constants `SHOW_ATTRIBUTE`, `SHOW_DOCUMENT`, `SHOW_DOCUMENT_TYPE`, `SHOW_NOTATION`, `SHOW_ENTITY`, and `SHOW_DOCUMENT_FRAGMENT` are meaningless here. Those nodes will never be passed to `LSParserFilter.acceptNode`.
      The constants used here are defined in [DOM Level 2 Traversal and Range].
  Methods
    `acceptNode`
      This method will be called by the parser at the completion of the parsing of each node. The node and all of its descendants will exist and be complete. The parent node will also exist, although it may be incomplete, i.e. it may have additional children that have not yet been parsed. Attribute nodes are never passed to this function.
      From within this method, the new node may be freely modified - children may be added or removed, text nodes modified, etc. The state of the rest of the document outside this node is not defined, and the affect of any attempt to navigate to, or to modify any other part of the document is undefined.
      For validating parsers, the checks are made on the original document, before any modification by the filter. No validity checks are made on any document modifications made by the filter.
      If this new node is rejected, the parser might reuse the new node and any of its descendants.
      Parameters
      `nodeArg` of type `Node`
        The newly constructed element. At the time this method is called, the element is complete - it has all of its children (and their children, recursively) and attributes, and is attached as a child to its parent.
      Return Value

      `unsigned short` | `FILTER_ACCEPT` if this `Node` should be included in the DOM document being built. `FILTER_REJECT` if the `Node` and all of its children should be rejected. `FILTER_SKIP` if the `Node` should be skipped and the `Node` should be replaced by all the children of the `Node`. `FILTER_INTERRUPT` if the filter wants to stop the processing of the document. Interrupting the processing of the document does no longer guarantee that the resulting DOM tree is XML well-formed. The `Node` is accepted and will be the last completely parsed node.

      No Exceptions
    `startElement`
      The parser will call this method after each `Element` start tag has been scanned, but before the remainder of the `Element` is processed. The intent is to allow the element, including any children, to be efficiently skipped. Note that only element nodes are passed to the `startElement` function.
      The element node passed to `startElement` for filtering will include all of the Element's attributes, but none of the children nodes. The Element may not yet be in place in the document being constructed (it may not have a parent node.)
      A `startElement` filter function may access or change the attributes for the Element. Changing Namespace declarations will have no effect on namespace resolution by the parser.
      For efficiency, the Element node passed to the filter may not be the same one as is actually placed in the tree if the node is accepted. And the actual node (node object identity) may be reused during the process of reading in and filtering a document.
      Parameters
      `elementArg` of type `Element`
        The newly encountered element. At the time this method is called, the element is incomplete - it will have its attributes, but no children.
      Return Value

      `unsigned short` | `FILTER_ACCEPT` if the `Element` should be included in the DOM document being built. `FILTER_REJECT` if the `Element` and all of its children should be rejected. `FILTER_SKIP` if the `Element` should be skipped. All of its children are inserted in place of the skipped `Element` node. `FILTER_INTERRUPT` if the filter wants to stop the processing of the document. Interrupting the processing of the document does no longer guarantee that the resulting DOM tree is XML well-formed. The `Element` is rejected. Returning any other values will result in unspecified behavior.

      No Exceptions
Interface LSProgressEvent

  This interface represents a progress event object that notifies the application about progress as a document is parsed. It extends the `Event` interface defined in [DOM Level 3 Events].

  The units used for the attributes `position` and `totalSize` are not specified and can be implementation and input dependent.

  IDL Definition

        interface LSProgressEvent : events::Event {
          readonly attribute LSInput         input;
          readonly attribute unsigned long   position;
          readonly attribute unsigned long   totalSize;
        };

  Attributes
    `input` of type `LSInput`, readonly
      The input source that is being parsed.
    `position` of type `unsigned long`, readonly
      The current position in the input source, including all external entities and other resources that have been read.
    `totalSize` of type `unsigned long`, readonly
      The total size of the document including all external resources, this number might change as a document is being parsed if references to more external resources are seen. A value of `0` is returned if the total size cannot be determined or estimated.
Interface LSLoadEvent

  This interface represents a load event object that signals the completion of a document load.

  IDL Definition

        interface LSLoadEvent : events::Event {
          readonly attribute Document        newDocument;
          readonly attribute LSInput         input;
        };

  Attributes
    `input` of type `LSInput`, readonly
      The input source that was parsed.
    `newDocument` of type `Document`, readonly
      The document that finished loading.
Interface LSSerializer

  A `LSSerializer` provides an API for serializing (writing) a DOM document out into XML. The XML data is written to a string or an output stream. Any changes or fixups made during the serialization affect only the serialized data. The `Document` object and its children are never altered by the serialization operation.

  During serialization of XML data, namespace fixup is done as defined in [DOM Level 3 Core], Appendix B. [DOM Level 2 Core] allows empty strings as a real namespace URI. If the `namespaceURI` of a `Node` is empty string, the serialization will treat them as `null`, ignoring the prefix if any.

  `LSSerializer` accepts any node type for serialization. For nodes of type `Document` or `Entity`, well-formed XML will be created when possible (well-formedness is guaranteed if the document or entity comes from a parse operation and is unchanged since it was created). The serialized output for these node types is either as a XML document or an External XML Entity, respectively, and is acceptable input for an XML parser. For all other types of nodes the serialized form is implementation dependent.

  Within a `Document`, `DocumentFragment`, or `Entity` being serialized, `Nodes` are processed as follows

  - `Document` nodes are written, including the XML declaration (unless the parameter "xml-declaration" is set to `false`) and a DTD subset, if one exists in the DOM. Writing a `Document` node serializes the entire document.
  - `Entity` nodes, when written directly by `LSSerializer.write`, outputs the entity expansion but no namespace fixup is done. The resulting output will be valid as an external entity.
  - If the parameter "entities" is set to `true`, `EntityReference` nodes are serialized as an entity reference of the form "`&entityName;`" in the output. Child nodes (the expansion) of the entity reference are ignored. If the parameter "entities" is set to `false`, only the children of the entity reference are serialized. `EntityReference` nodes with no children (no corresponding `Entity` node or the corresponding `Entity` nodes have no children) are always serialized.
  - `CDATAsections` containing content characters that cannot be represented in the specified output encoding are handled according to the "split-cdata-sections" parameter.
    If the parameter is set to `true`, `CDATAsections` are split, and the unrepresentable characters are serialized as numeric character references in ordinary content. The exact position and number of splits is not specified.
    If the parameter is set to `false`, unrepresentable characters in a `CDATAsection` are reported as `"wf-invalid-character"` errors if the parameter "well-formed" is set to `true`. The error is not recoverable - there is no mechanism for supplying alternative characters and continuing with the serialization.
  - `DocumentFragment` nodes are serialized by serializing the children of the document fragment in the order they appear in the document fragment.
  - All other node types (Element, Text, etc.) are serialized to their corresponding XML source form.

  Note: The serialization of a `Node` does not always generate a well-formed XML document, i.e. a `LSParser` might throw fatal errors when parsing the resulting serialization.

  Within the character data of a document (outside of markup), any characters that cannot be represented directly are replaced with character references. Occurrences of '<' and '&' are replaced by the predefined entities &lt; and &amp;. The other predefined entities (&gt;, &apos;, and &quot;) might not be used, except where needed (e.g. using &gt; in cases such as ']]>'). Any characters that cannot be represented directly in the output character encoding are serialized as numeric character references (and since character encoding standards commonly use hexadecimal representations of characters, using the hexadecimal representation when serializing character references is encouraged).

  To allow attribute values to contain both single and double quotes, the apostrophe or single-quote character (') may be represented as "&apos;", and the double-quote character (") as "&quot;". New line characters and other characters that cannot be represented directly in attribute values in the output character encoding are serialized as a numeric character reference.

  Within markup, but outside of attributes, any occurrence of a character that cannot be represented in the output character encoding is reported as a `DOMError` fatal error. An example would be serializing the element <LaCañada/> with `encoding="us-ascii"`. This will result with a generation of a `DOMError` "wf-invalid-character-in-node-name" (as proposed in "well-formed").

  When requested by setting the parameter "normalize-characters" on `LSSerializer` to true, character normalization is performed according to the definition of fully normalized characters included in appendix E of [XML 1.1] on all data to be serialized, both markup and character data. The character normalization process affects only the data as it is being written; it does not alter the DOM's view of the document after serialization has completed.

  Implementations are required to support the encodings "UTF-8", "UTF-16", "UTF-16BE", and "UTF-16LE" to guarantee that data is serializable in all encodings that are required to be supported by all XML parsers. When the encoding is UTF-8, whether or not a byte order mark is serialized, or if the output is big-endian or little-endian, is implementation dependent. When the encoding is UTF-16, whether or not the output is big-endian or little-endian is implementation dependent, but a Byte Order Mark must be generated for non-character outputs, such as `LSOutput.byteStream` or `LSOutput.systemId`. If the Byte Order Mark is not generated, a "byte-order-mark-needed" warning is reported. When the encoding is UTF-16LE or UTF-16BE, the output is big-endian (UTF-16BE) or little-endian (UTF-16LE) and the Byte Order Mark is not be generated. In all cases, the encoding declaration, if generated, will correspond to the encoding used during the serialization (e.g. `encoding="UTF-16"` will appear if UTF-16 was requested).

  Namespaces are fixed up during serialization, the serialization process will verify that namespace declarations, namespace prefixes and the namespace URI associated with elements and attributes are consistent. If inconsistencies are found, the serialized form of the document will be altered to remove them. The method used for doing the namespace fixup while serializing a document is the algorithm defined in Appendix B.1, "Namespace normalization", of [DOM Level 3 Core].

  While serializing a document, the parameter "discard-default-content" controls whether or not non-specified data is serialized.

  While serializing, errors and warnings are reported to the application through the error handler (`LSSerializer.domConfig`'s "error-handler" parameter). This specification does in no way try to define all possible errors and warnings that can occur while serializing a DOM node, but some common error and warning cases are defined. The types (`DOMError.type`) of errors and warnings defined by this specification are:

  `"no-output-specified" [fatal]`
    Raised when writing to a `LSOutput` if no output is specified in the `LSOutput`.
  `"unbound-prefix-in-entity-reference" [fatal]`
    Raised if the configuration parameter "namespaces" is set to `true` and an entity whose replacement text contains unbound namespace prefixes is referenced in a location where there are no bindings for the namespace prefixes.
  `"unsupported-encoding" [fatal]`
    Raised if an unsupported encoding is encountered.

  In addition to raising the defined errors and warnings, implementations are expected to raise implementation specific errors and warnings for any other error and warning cases such as IO errors (file not found, permission denied,...) and so on.

  IDL Definition

        interface LSSerializer {
          readonly attribute DOMConfiguration domConfig;
                   attribute DOMString       newLine;
                   attribute LSSerializerFilter filter;
          boolean            write(in Node nodeArg,
                                   in LSOutput destination)
                                                raises(LSException);
          boolean            writeToURI(in Node nodeArg,
                                        in DOMString uri)
                                                raises(LSException);
          DOMString          writeToString(in Node nodeArg)
                                                raises(DOMException,
                                                       LSException);
        };

  Attributes
    `domConfig` of type `DOMConfiguration`, readonly
      The `DOMConfiguration` object used by the `LSSerializer` when serializing a DOM node.
      In addition to the parameters recognized by the DOMConfiguration interface defined in [DOM Level 3 Core], the `DOMConfiguration` objects for `LSSerializer` adds, or modifies, the following parameters:
      `"canonical-form"`
        `true`
          [optional]
          Writes the document according to the rules specified in [Canonical XML]. In addition to the behavior described in "canonical-form" [DOM Level 3 Core], setting this parameter to `true` will set the parameters "format-pretty-print", "discard-default-content", and "xml-declaration", to `false`. Setting one of those parameters to `true` will set this parameter to `false`. Serializing an XML 1.1 document when "canonical-form" is `true` will generate a fatal error.
        `false`
          [required] (default)
          Do not canonicalize the output.
      `"discard-default-content"`
        `true`
          [required] (default)
          Use the `Attr.specified` attribute to decide what attributes should be discarded. Note that some implementations might use whatever information available to the implementation (i.e. XML schema, DTD, the `Attr.specified` attribute, and so on) to determine what attributes and content to discard if this parameter is set to `true`.
        `false`
          [required]
          Keep all attributes and all content.
      `"format-pretty-print"`
        `true`
          [optional]
          Formatting the output by adding whitespace to produce a pretty-printed, indented, human-readable form. The exact form of the transformations is not specified by this specification. Pretty-printing changes the content of the document and may affect the validity of the document, validating implementations should preserve validity.
        `false`
          [required] (default)
          Don't pretty-print the result.
      `"ignore-unknown-character-denormalizations"`
        `true`
          [required] (default)
          If, while verifying full normalization when [XML 1.1] is supported, a character is encountered for which the normalization properties cannot be determined, then raise a `"unknown-character-denormalization"` warning (instead of raising an error, if this parameter is not set) and ignore any possible denormalizations caused by these characters.
        `false`
          [optional]
          Report a fatal error if a character is encountered for which the processor cannot determine the normalization properties.
      `"normalize-characters"`
        This parameter is equivalent to the one defined by `DOMConfiguration` in [DOM Level 3 Core]. Unlike in the Core, the default value for this parameter is `true`. While DOM implementations are not required to support fully normalizing the characters in the document according to appendix E of [XML 1.1], this parameter must be activated by default if supported.
      `"xml-declaration"`
        `true`
          [required] (default)
          If a `Document`, `Element`, or `Entity` node is serialized, the XML declaration, or text declaration, should be included. The version (`Document.xmlVersion` if the document is a Level 3 document and the version is non-null, otherwise use the value "1.0"), and the output encoding (see `LSSerializer.write` for details on how to find the output encoding) are specified in the serialized XML declaration.
        `false`
          [required]
          Do not serialize the XML and text declarations. Report a `"xml-declaration-needed"` warning if this will cause problems (i.e. the serialized data is of an XML version other than [XML 1.0], or an encoding would be needed to be able to re-parse the serialized data).
    `filter` of type `LSSerializerFilter`
      When the application provides a filter, the serializer will call out to the filter before serializing each Node. The filter implementation can choose to remove the node from the stream or to terminate the serialization early.
      The filter is invoked after the operations requested by the `DOMConfiguration` parameters have been applied. For example, CDATA sections won't be passed to the filter if "cdata-sections" is set to `false`.
    `newLine` of type `DOMString`
      The end-of-line sequence of characters to be used in the XML being written out. Any string is supported, but XML treats only a certain set of characters sequence as end-of-line (See section 2.11, "End-of-Line Handling" in [XML 1.0], if the serialized content is XML 1.0 or section 2.11, "End-of-Line Handling" in [XML 1.1], if the serialized content is XML 1.1). Using other character sequences than the recommended ones can result in a document that is either not serializable or not well-formed).
      On retrieval, the default value of this attribute is the implementation specific default end-of-line sequence. DOM implementations should choose the default to match the usual convention for text files in the environment being used. Implementations must choose a default sequence that matches one of those allowed by XML 1.0 or XML 1.1, depending on the serialized content. Setting this attribute to `null` will reset its value to the default value.
  Methods
    `write`
      Serialize the specified node as described above in the general description of the `LSSerializer` interface. The output is written to the supplied `LSOutput`.
      When writing to a `LSOutput`, the encoding is found by looking at the encoding information that is reachable through the `LSOutput` and the item to be written (or its owner document) in this order:
      1. `LSOutput.encoding`,
      2. `Document.inputEncoding`,
      3. `Document.xmlEncoding`.
      If no encoding is reachable through the above properties, a default encoding of "UTF-8" will be used. If the specified encoding is not supported an "unsupported-encoding" fatal error is raised.
      If no output is specified in the `LSOutput`, a "no-output-specified" fatal error is raised.
      The implementation is responsible of associating the appropriate media type with the serialized data.
      When writing to a HTTP URI, a HTTP PUT is performed. When writing to other types of URIs, the mechanism for writing the data to the URI is implementation dependent.
      Parameters
      `nodeArg` of type `Node`
        The node to serialize.
      `destination` of type `LSOutput`
        The destination for the serialized DOM.
      Return Value

      `boolean` | Returns `true` if `node` was successfully serialized. Return `false` in case the normal processing stopped but the implementation kept serializing the document; the result of the serialization being implementation dependent then.

      Exceptions

      `LSException` | SERIALIZE_ERR: Raised if the `LSSerializer` was unable to serialize the node. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

    `writeToString`
      Serialize the specified node as described above in the general description of the `LSSerializer` interface. The output is written to a `DOMString` that is returned to the caller. The encoding used is the encoding of the `DOMString` type, i.e. UTF-16. Note that no Byte Order Mark is generated in a `DOMString` object.
      Parameters
      `nodeArg` of type `Node`
        The node to serialize.
      Return Value

      `DOMString` | Returns the serialized data.

      Exceptions

      `DOMException` | DOMSTRING_SIZE_ERR: Raised if the resulting string is too long to fit in a `DOMString`.
      `LSException` | SERIALIZE_ERR: Raised if the `LSSerializer` was unable to serialize the node. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

    `writeToURI`
      A convenience method that acts as if `LSSerializer.write` was called with a `LSOutput` with no encoding specified and `LSOutput.systemId` set to the `uri` argument.
      Parameters
      `nodeArg` of type `Node`
        The node to serialize.
      `uri` of type `DOMString`
        The URI to write to.
      Return Value

      `boolean` | Returns `true` if `node` was successfully serialized. Return `false` in case the normal processing stopped but the implementation kept serializing the document; the result of the serialization being implementation dependent then.

      Exceptions

      `LSException` | SERIALIZE_ERR: Raised if the `LSSerializer` was unable to serialize the node. DOM applications should attach a `DOMErrorHandler` using the parameter "error-handler" if they wish to get details on the error.

Interface LSOutput

  This interface represents an output destination for data.

  This interface allows an application to encapsulate information about an output destination in a single object, which may include a URI, a byte stream (possibly with a specified encoding), a base URI, and/or a character stream.

  The exact definitions of a byte stream and a character stream are binding dependent.

  The application is expected to provide objects that implement this interface whenever such objects are needed. The application can either provide its own objects that implement this interface, or it can use the generic factory method `DOMImplementationLS.createLSOutput()` to create objects that implement this interface.

  The `LSSerializer` will use the `LSOutput` object to determine where to serialize the output to. The `LSSerializer` will look at the different outputs specified in the `LSOutput` in the following order to know which one to output to, the first one that is not null and not an empty string will be used:

  1. `LSOutput.characterStream`
  2. `LSOutput.byteStream`
  3. `LSOutput.systemId`

  `LSOutput` objects belong to the application. The DOM implementation will never modify them (though it may make copies and modify the copies, if necessary).

  IDL Definition

        interface LSOutput {
          // Depending on the language binding in use,
          // this attribute may not be available.
                   attribute LSWriter        characterStream;
                   attribute LSOutputStream  byteStream;
                   attribute DOMString       systemId;
                   attribute DOMString       encoding;
        };

  Attributes
    `byteStream` of type `LSOutputStream`
      An attribute of a language and binding dependent type that represents a writable stream of bytes.
    `characterStream` of type `LSWriter`
    Depending on the language binding in use, this attribute may not be available.
      An attribute of a language and binding dependent type that represents a writable stream to which 16-bit units can be output.
    `encoding` of type `DOMString`
      The character encoding to use for the output. The encoding must be a string acceptable for an XML encoding declaration ([XML 1.0] section 4.3.3 "Character Encoding in Entities"), it is recommended that character encodings registered (as charsets) with the Internet Assigned Numbers Authority [IANA-CHARSETS] should be referred to using their registered names.
    `systemId` of type `DOMString`
      The system identifier, a URI reference [IETF RFC 2396], for this output destination.
      If the system ID is a relative URI reference (see section 5 in [IETF RFC 2396]), the behavior is implementation dependent.
Interface LSSerializerFilter

  `LSSerializerFilter`s provide applications the ability to examine nodes as they are being serialized and decide what nodes should be serialized or not. The `LSSerializerFilter` interface is based on the `NodeFilter` interface defined in [DOM Level 2 Traversal and Range].

  `Document`, `DocumentType`, `DocumentFragment`, `Notation`, `Entity`, and children of `Attr` nodes are not passed to the filter. The child nodes of an `EntityReference` node are only passed to the filter if the `EntityReference` node is skipped by the method `LSParserFilter.acceptNode()`.

  When serializing an `Element`, the element is passed to the filter before any of its attributes are passed to the filter. Namespace declaration attributes, and default attributes (except in the case when "discard-default-content" is set to `false`), are never passed to the filter.

  The result of any attempt to modify a node passed to a `LSSerializerFilter` is implementation dependent.

  DOM applications must not raise exceptions in a filter. The effect of throwing exceptions from a filter is DOM implementation dependent.

  For efficiency, a node passed to the filter may not be the same as the one that is actually in the tree. And the actual node (node object identity) may be reused during the process of filtering and serializing a document.

  IDL Definition

        interface LSSerializerFilter : traversal::NodeFilter {
          readonly attribute unsigned long   whatToShow;
        };

  Attributes
    `whatToShow` of type `unsigned long`, readonly
      Tells the `LSSerializer` what types of nodes to show to the filter. If a node is not shown to the filter using this attribute, it is automatically serialized. See `NodeFilter` for definition of the constants. The constants `SHOW_DOCUMENT`, `SHOW_DOCUMENT_TYPE`, `SHOW_DOCUMENT_FRAGMENT`, `SHOW_NOTATION`, and `SHOW_ENTITY` are meaningless here, such nodes will never be passed to a `LSSerializerFilter`.
      Unlike [DOM Level 2 Traversal and Range], the `SHOW_ATTRIBUTE` constant indicates that the `Attr` nodes are shown and passed to the filter.
      The constants used here are defined in [DOM Level 2 Traversal and Range].