class type resolver =object..end
method init_rep_encoding : Pxp_types.rep_encoding -> unitLexing.lexbuf (and as its advanced version, 
 Netulex.ULB.unicode_lexbuf).
 After creating a resolver, one must invoke the two methods
 init_rep_encoding and init_warner to set the internal encoding of
 strings and the warner object, respectively. This is normally
 already done by the parsing core.
 It is not necessary to invoke these two methods for a fresh
 clone.
It is possible that the character encoding of the source and the internal encoding of the parser are different. To cope with this, one of the tasks of the resolver is to recode the characters of the input source into the internal character encoding.
Note that there are several ways of determining the encoding of the input: (1) It is possible that the transport protocol (e.g. HTTP) transmits the encoding, and (2) it is possible to inspect the beginning of the file, and to analyze:
<?xml ... encoding="xyz" ...?>. The encoding found here is
         to be used.
 A resolver is like a file: it must be opened before one can work
 with it, and it should be closed after all operations on it have been
 done. The method open_rid is called with the resolver ID as argument
 and it must return the lexbuf reading from the external resource.
 (There is also the old method open_in that expects an ext_id as
 argument. It is less powerful and should not be used any longer.)
 The method close_in does not require an argument.
 It is allowed to re-open a resolver after it has been closed. It is
 forbidden to open a resolver again while it is open.
 It is allowed to close a resolver several times: If close_in is
 invoked while the resolver is already closed, nothing happens.
 The method open_rid may raise Not_competent to indicate that this
 resolver is not able to open this type of IDs.
 If open_rid gets a PUBLIC ID, it can be assumed that the string
 is already normalized (concerning whitespace).
 The method change_encoding is called from the parser after the
 analysis of case (2) has been done; the argument is either the
 string name of the encoding, or the empty string to indicate
 that no XML declaration was found. It is guaranteed that
 change_encoding is invoked after only a few tokens of the
 file. The resolver should react as follows:
change_encoding.change_encoding must
                          be compatible with UTF-16. This should be
                          checked, and violations should be reported.change_encoding has not yet
 been invoked, the lexbuf contains at most one character (which may
 be represented by multiple bytes); i.e. the lexbuf is created by
 Lexing.from_function, and the function puts only one character into
 the buffer at once.
 After change_encoding has been invoked, there is no longer a limit
 on the lexbuf size.
 The reason for this rule is that you know exactly the character where
 the encoding changes to the encoding passed by change_encoding.
 The method clone may be invoked for open or closed resolvers.
 Basically, clone returns a new resolver which is always closed.
 If the original resolver is already closed, the clone is simply a clone.
 If the original resolver is open at the moment of cloning, this applies:
 If the clone is later opened for a relative system ID (i.e. relative
 URL), the clone must interpret this ID relative to the ID of the
 original resolver.
method init_warner : Pxp_types.symbolic_warnings option ->
       Pxp_types.collect_warnings -> unitmethod rep_encoding : Pxp_types.rep_encodinginit_rep_encodingmethod open_in : Pxp_types.ext_id -> lexer_sourceopen_rid.
 This method may raise Not_competent if the object does not know
 how to handle this ext_id.method open_rid : Pxp_types.resolver_id -> lexer_sourceext_id but works in the same way.method close_in : unitmethod change_encoding : string -> unitmethod clone : resolvermethod active_id : Pxp_types.resolver_idopen_rid where unused components have been set to None. The
 resolver ID returned by active_id plays an important role when
 expanding relative URLs.