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NAME

       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
       facility.

       XML content
       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.

       Content creation
       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 "http://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.

       Content type
       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
       mode.

       # 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)
       service.

       XmlContent
       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
       encoding.

       Predicate

              xml-content-p

       Inheritance

              XmlDocumentMime

       Constructors

              XmlContent (String)
              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.

       Methods

              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
              object name.

       XmlFeature
       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.

       Predicate

              xhtml-feature-p

       Inheritance

              Nameable

       Methods

              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
              level.

              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
              processor.

       XmlProcessor
       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
       produced.

       Predicate

              xml-processor-p

       Inheritance

              Object

       Constructors

              XmlProcessor (none)
              The XmlProcessor constructor creates  a  default  xml  processor
              without any feature.

       Methods

              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
              chain.

              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.

       XmlInclude
       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.

       Predicate

              xml-include-p

       Inheritance

              XmlFeature

       Constructors

              XmlInclude (none)
              The   XmlInclude  constructor  creates  a  default  xml  include
              feature. The default feature processing level is 10.

              XmlInclude (Integer)
              The XmlInclude constructor creates a xml include feature with  a
              processing level. The integer argument is the feature processing
              level to set.