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xpe: xml processing environment service
xpe - xml processing environment service
XML PROCESSING ENVIRONMENT SERVICE
This chapter covers the fundamental objects of the XML processing
environment service. This service provides the support for processing
xml document that could be accessed locally or other the Internet. In
particular, the processing environment supports the XML include
The XmlContent class is an extension of the XML document object that
provides the service for loading a XML document locally or from the
Internet. The class operates with an uri, which permits to selects the
appropriate loader from the uri scheme.
The XmlContent operates with an uri that permits to select the
appropriate loader. If the uri scheme is a file scheme, the content is
retrieved locally. If the uri scheme is http, the content is retrieved
by establishing a http connection over the Internet.
# create a document from a local file
const xdoc (afnix:xpe:XmlContent "file:///home/afnix/file.xml")
When the uri scheme is a file, the uri authority is empty (hence the
double //) and the path indicates the file to parse. The XmlContent
object is derived from the XmlDocument object which contains the parsed
tree with the XmlRoot object.
# create a document from a http connection
const xdoc (afnix:xpe:XmlContent "//www.afnix.org/index.xht")
When the uri scheme is a http scheme, the document is downloaded by
establishing an http connection with the uri authority. When the http
header is received, the content is parsed to create a valid xml
document. If the http response header indicates that the page has moved
and a new location is provided, the object manages automatically to
follow such location.
Content and document name
Since the XmlContent object is derived from the XmlContent object, the
content object is defined with a uri name and a document name. Under
normal circumstances, the document name is derived from the content
name by normalizing it. The content name is the object constructor
name, while the document name is the normalized document name. The get-
name method returns the content name while the get-document-name method
returns the document name.
# create a document by name
const xdoc (afnix:xpe:XmlContent "file" "file.xml")
In the previous example, a xml content object is created by name with a
document name. It is the document name that gets normalized. Therefore
in the previous example, the file.xml document name is normalized into
a file uri. The normalization rule always favor the file scheme. This
means that without a scheme, the file scheme is automatically added.
Many times, the content type cannot be detected from the uri name. Once
opened, if the content header provides a clue about the content type,
the opened input stream get adjusted automatically to reflect this
fact. However, this situation does not occurs often and with http
scheme, the content type header response does not often provides the
character encoding associated with the stream. For this reason, the
XmlContent constructor provides a mechanism to accept the encoding
# create a new content by name and encoding mode
const xdoc (afnix:xpe:XmlContent "file" "file.xml" "UTF-8")
XML PROCESSING ENVIRONMENT SERVICE REFERENCE
This appendix is a reference of the XML Processing Environment (xpe)
The XmlContent class is an extension of the xml document class that
operates at the uri level. If the uri is a local file the xml document
is created from an input file stream. If the uri is an url, the content
is fetched automatically. The class constructors permit to separate the
content name from the document name and also to specify the content
The XmlContent constructor creates a xml document by name. The
document name is the normalized uri name that always favor a
file scheme in the absence of it.
XmlContent (String String)
The XmlContent constructor creates a xml document by name. The
first argument is the content name. The second argument is the
document name which is normalized to form the uri name used to
load the document.
XmlContent (String String String)
The XmlContent constructor creates a xml document by name and
encoding mode. The first argument is the content name. The
second argument is the document name which is normalized to form
the uri name used to load the document. The third argument is
the content character encoding.
get-document-uri -> String (none)
The get-document-uri method returns the document normalized uri.
get-document-name -> String (none)
The get-document-name method returns the object document name.
This method complements the get-name method which returns the
The XmlFeature class is a xml processor base class that defines a
processing feature. A processing feature is defined by name and
information with a processing level. The default processing level is
null. When the processor is called, it calls sequentially and in
ascending order all features.
get-info -> String (none)
The get-info method returns the xml feature information string.
The feature name is available from the get-name provided by the
Nameable base class.
set-processing-level -> none (Integer)
The set-processing-level method sets the feature processing
level. The integer argument is the level to set.
get-processing-level -> Integer (none)
The get-processing-level method returns the feature processing
processing-level-p -> Boolean (Integer)
The processing-level-p predicate returns true if the integer
argument equal the feature processing level.
process -> XmlContent (XmlContent)
The process method process the input xml content and returns a
new xml content. The method is automatically called by the xml
The XmlProcessor class is a global class designed to operate on a xml
content. The xml processor provides several features that can be
enabled prior the document processor. Once the features are defined,
the 'process' method can be called and a new xml content can be
The XmlProcessor constructor creates a default xml processor
without any feature.
feature-length -> Integer (none)
The feature-length method returns the number of features defined
in the xml processor.
add-feature -> none (XmlFeature)
The add-feature method adds a feature object to the processor.
The feature processing level does not have to be sorted prior
the insertion. Adding multiple feature creates a processor
get-feature -> XmlFeature (Integer)
The get-feature method return a processor feature by index.
process -> XmlFeature (XmlFeature)
The process method create a new xml content by calling
processing feature chain. The feature chain consists of feature
object sorted in ascending order. If the processor contains only
one feature, calling the process method is equivalent to call
the XmlFeature same method.
The XmlInclude class is a xml processor feature class designed to
handle the "XInclude" schema that permits to include xml document. The
feature operates recursively by scanning the document for a
"xi:include" tag and replacing the content by the appropriate tree. The
feature operates recursively unless specified otherwise.
The XmlInclude constructor creates a default xml include
feature. The default feature processing level is 10.
The XmlInclude constructor creates a xml include feature with a
processing level. The integer argument is the feature processing
level to set.