1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2000-2020, University of Amsterdam
    7                              VU University Amsterdam
    8                              CWI, Amsterdam
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(sgml,
   38          [ load_html/3,                % +Input, -DOM, +Options
   39            load_xml/3,                 % +Input, -DOM, +Options
   40            load_sgml/3,                % +Input, -DOM, +Options
   41
   42            load_sgml_file/2,           % +File, -ListOfContent
   43            load_xml_file/2,            % +File, -ListOfContent
   44            load_html_file/2,           % +File, -Document
   45
   46            load_structure/3,           % +File, -Term, +Options
   47
   48            load_dtd/2,                 % +DTD, +File
   49            load_dtd/3,                 % +DTD, +File, +Options
   50            dtd/2,                      % +Type, -DTD
   51            dtd_property/2,             % +DTD, ?Property
   52
   53            new_dtd/2,                  % +Doctype, -DTD
   54            free_dtd/1,                 % +DTD
   55            open_dtd/3,                 % +DTD, +Options, -Stream
   56
   57            new_sgml_parser/2,          % -Parser, +Options
   58            free_sgml_parser/1,         % +Parser
   59            set_sgml_parser/2,          % +Parser, +Options
   60            get_sgml_parser/2,          % +Parser, +Options
   61            sgml_parse/2,               % +Parser, +Options
   62
   63            sgml_register_catalog_file/2, % +File, +StartOrEnd
   64
   65            xml_quote_attribute/3,      % +In, -Quoted, +Encoding
   66            xml_quote_cdata/3,          % +In, -Quoted, +Encoding
   67            xml_quote_attribute/2,      % +In, -Quoted
   68            xml_quote_cdata/2,          % +In, -Quoted
   69            xml_name/1,                 % +In
   70            xml_name/2,                 % +In, +Encoding
   71
   72            xsd_number_string/2,        % ?Number, ?String
   73            xsd_time_string/3,          % ?Term, ?Type, ?String
   74
   75            xml_basechar/1,             % +Code
   76            xml_ideographic/1,          % +Code
   77            xml_combining_char/1,       % +Code
   78            xml_digit/1,                % +Code
   79            xml_extender/1,             % +Code
   80
   81            iri_xml_namespace/2,        % +IRI, -Namespace
   82            iri_xml_namespace/3,        % +IRI, -Namespace, -LocalName
   83            xml_is_dom/1                % +Term
   84          ]).   85:- autoload(library(error),[instantiation_error/1]).   86:- autoload(library(iostream),[open_any/5,close_any/1]).   87:- autoload(library(lists),[member/2,selectchk/3]).   88:- autoload(library(option),[select_option/3,merge_options/3]).   89
   90:- meta_predicate
   91    load_structure(+, -, :),
   92    load_html(+, -, :),
   93    load_xml(+, -, :),
   94    load_sgml(+, -, :).   95
   96:- predicate_options(load_structure/3, 3,
   97                     [ charpos(integer),
   98                       cdata(oneof([atom,string])),
   99                       defaults(boolean),
  100                       dialect(oneof([html,html4,html5,sgml,xhtml,xhtml5,xml,xmlns])),
  101                       doctype(atom),
  102                       dtd(any),
  103                       encoding(oneof(['iso-8859-1', 'utf-8', 'us-ascii'])),
  104                       entity(atom,atom),
  105                       keep_prefix(boolean),
  106                       file(atom),
  107                       line(integer),
  108                       offset(integer),
  109                       number(oneof([token,integer])),
  110                       qualify_attributes(boolean),
  111                       shorttag(boolean),
  112                       case_sensitive_attributes(boolean),
  113                       case_preserving_attributes(boolean),
  114                       system_entities(boolean),
  115                       max_memory(integer),
  116                       space(oneof([sgml,preserve,default,remove,strict])),
  117                       xmlns(atom),
  118                       xmlns(atom,atom),
  119                       pass_to(sgml_parse/2, 2)
  120                     ]).  121:- predicate_options(load_html/3, 3,
  122                     [ pass_to(load_structure/3, 3)
  123                     ]).  124:- predicate_options(load_xml/3, 3,
  125                     [ pass_to(load_structure/3, 3)
  126                     ]).  127:- predicate_options(load_sgml/3, 3,
  128                     [ pass_to(load_structure/3, 3)
  129                     ]).  130:- predicate_options(load_dtd/3, 3,
  131                     [ dialect(oneof([sgml,xml,xmlns])),
  132                       pass_to(open/4, 4)
  133                     ]).  134:- predicate_options(sgml_parse/2, 2,
  135                     [ call(oneof([begin,end,cdata,pi,decl,error,xmlns,urlns]),
  136                            callable),
  137                       cdata(oneof([atom,string])),
  138                       content_length(integer),
  139                       document(-any),
  140                       max_errors(integer),
  141                       parse(oneof([file,element,content,declaration,input])),
  142                       source(any),
  143                       syntax_errors(oneof([quiet,print,style])),
  144                       xml_no_ns(oneof([error,quiet]))
  145                     ]).  146:- predicate_options(new_sgml_parser/2, 2,
  147                     [ dtd(any)
  148                     ]).

  178:- multifile user:file_search_path/2.  179:- dynamic   user:file_search_path/2.  180
  181user:file_search_path(dtd, '.').
  182user:file_search_path(dtd, swi('library/DTD')).
  183
  184sgml_register_catalog_file(File, Location) :-
  185    prolog_to_os_filename(File, OsFile),
  186    '_sgml_register_catalog_file'(OsFile, Location).
  187
  188:- use_foreign_library(foreign(sgml2pl)).  189
  190register_catalog(Base) :-
  191    absolute_file_name(dtd(Base),
  192                           [ extensions([soc]),
  193                             access(read),
  194                             file_errors(fail)
  195                           ],
  196                           SocFile),
  197    sgml_register_catalog_file(SocFile, end).
  198
  199:- initialization
  200    ignore(register_catalog('HTML4')).  201
  202
  203                 /*******************************
  204                 *         DTD HANDLING         *
  205                 *******************************/
  206
  207/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  208Note that concurrent access to DTD objects  is not allowed, and hence we
  209will allocate and destroy them in each   thread.  Possibibly it would be
  210nicer to find out why  concurrent  access   to  DTD's  is  flawed. It is
  211diagnosed to mess with the entity resolution by Fabien Todescato.
  212- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  213
  214:- thread_local
  215    current_dtd/2.  216:- volatile
  217    current_dtd/2.  218:- thread_local
  219    registered_cleanup/0.  220:- volatile
  221    registered_cleanup/0.  222
  223:- multifile
  224    dtd_alias/2.  225
  226:- create_prolog_flag(html_dialect, html5, [type(atom)]).  227
  228dtd_alias(html4, 'HTML4').
  229dtd_alias(html5, 'HTML5').
  230dtd_alias(html,  DTD) :-
  231    current_prolog_flag(html_dialect, Dialect),
  232    dtd_alias(Dialect, DTD).

 dtd(+Type, -DTD) is det

DTD is a DTD object created from the file dtd(Type). Loaded DTD objects are cached. Note that DTD objects may not be shared between threads. Therefore, dtd/2 maintains the pool of DTD objects using a thread_local predicate. DTD objects are destroyed if a thread terminates.

Errors

- existence_error(source_sink, dtd(Type))

  244dtd(Type, DTD) :-
  245    current_dtd(Type, DTD),
  246    !.
  247dtd(Type, DTD) :-
  248    new_dtd(Type, DTD),
  249    (   dtd_alias(Type, Base)
  250    ->  true
  251    ;   Base = Type
  252    ),
  253    absolute_file_name(dtd(Base),
  254                       [ extensions([dtd]),
  255                         access(read)
  256                       ], DtdFile),
  257    load_dtd(DTD, DtdFile),
  258    register_cleanup,
  259    asserta(current_dtd(Type, DTD)).

 load_dtd(+DTD, +DtdFile, +Options)

Load DtdFile into a DTD. Defined options are:

dialect(+Dialect)

Dialect to use (xml, xmlns, sgml)

encoding(+Encoding)

Encoding of DTD file

Arguments:

DTD	- is a fresh DTD object, normally created using new_dtd/1.

  274load_dtd(DTD, DtdFile) :-
  275    load_dtd(DTD, DtdFile, []).
  276load_dtd(DTD, DtdFile, Options) :-
  277    sgml_open_options(sgml:Options, OpenOptions, sgml:DTDOptions),
  278    setup_call_cleanup(
  279        open_dtd(DTD, DTDOptions, DtdOut),
  280        setup_call_cleanup(
  281            open(DtdFile, read, DtdIn, OpenOptions),
  282            copy_stream_data(DtdIn, DtdOut),
  283            close(DtdIn)),
  284        close(DtdOut)).

 destroy_dtds

Destroy DTDs cached by this thread as they will become unreachable anyway.

  291destroy_dtds :-
  292    (   current_dtd(_Type, DTD),
  293        free_dtd(DTD),
  294        fail
  295    ;   true
  296    ).

 register_cleanup

Register cleanup of DTDs created for this thread.

  302register_cleanup :-
  303    registered_cleanup,
  304    !.
  305register_cleanup :-
  306    (   thread_self(main)
  307    ->  at_halt(destroy_dtds)
  308    ;   current_prolog_flag(threads, true)
  309    ->  prolog_listen(this_thread_exit, destroy_dtds)
  310    ;   true
  311    ),
  312    assert(registered_cleanup).
  313
  314
  315                 /*******************************
  316                 *          EXAMINE DTD         *
  317                 *******************************/
  318
  319prop(doctype(_), _).
  320prop(elements(_), _).
  321prop(entities(_), _).
  322prop(notations(_), _).
  323prop(entity(E, _), DTD) :-
  324    (   nonvar(E)
  325    ->  true
  326    ;   '$dtd_property'(DTD, entities(EL)),
  327        member(E, EL)
  328    ).
  329prop(element(E, _, _), DTD) :-
  330    (   nonvar(E)
  331    ->  true
  332    ;   '$dtd_property'(DTD, elements(EL)),
  333        member(E, EL)
  334    ).
  335prop(attributes(E, _), DTD) :-
  336    (   nonvar(E)
  337    ->  true
  338    ;   '$dtd_property'(DTD, elements(EL)),
  339        member(E, EL)
  340    ).
  341prop(attribute(E, A, _, _), DTD) :-
  342    (   nonvar(E)
  343    ->  true
  344    ;   '$dtd_property'(DTD, elements(EL)),
  345        member(E, EL)
  346    ),
  347    (   nonvar(A)
  348    ->  true
  349    ;   '$dtd_property'(DTD, attributes(E, AL)),
  350        member(A, AL)
  351    ).
  352prop(notation(N, _), DTD) :-
  353    (   nonvar(N)
  354    ->  true
  355    ;   '$dtd_property'(DTD, notations(NL)),
  356        member(N, NL)
  357    ).
  358
  359dtd_property(DTD, Prop) :-
  360    prop(Prop, DTD),
  361    '$dtd_property'(DTD, Prop).
  362
  363
  364                 /*******************************
  365                 *             SGML             *
  366                 *******************************/

 load_structure(+Source, -ListOfContent, :Options) is det

Parse Source and return the resulting structure in ListOfContent. Source is handed to open_any/5, which allows for processing an extensible set of input sources.

A proper XML document contains only a single toplevel element whose name matches the document type. Nevertheless, a list is returned for consistency with the representation of element content.

The encoding(+Encoding) option is treated special for compatibility reasons:

• If Encoding is one of iso-8859-1, us-ascii or utf-8, the stream is opened in binary mode and the option is passed to the SGML parser.
• If Encoding is present, but not one of the above, the stream is opened in text mode using the given encoding.
• Otherwise (no Encoding), the stream is opened in binary mode and doing the correct decoding is left to the parser.

  390load_structure(Spec, DOM, Options) :-
  391    sgml_open_options(Options, OpenOptions, SGMLOptions),
  392    setup_call_cleanup(
  393        open_any(Spec, read, In, Close, OpenOptions),
  394        load_structure_from_stream(In, DOM, SGMLOptions),
  395        close_any(Close)).
  396
  397sgml_open_options(Options, OpenOptions, SGMLOptions) :-
  398    Options = M:Plain,
  399    (   select_option(encoding(Encoding), Plain, NoEnc)
  400    ->  (   sgml_encoding(Encoding)
  401        ->  merge_options(NoEnc, [type(binary)], OpenOptions),
  402            SGMLOptions = Options
  403        ;   OpenOptions = Plain,
  404            SGMLOptions = M:NoEnc
  405        )
  406    ;   merge_options(Plain, [type(binary)], OpenOptions),
  407        SGMLOptions = Options
  408    ).
  409
  410sgml_encoding(Enc) :-
  411    downcase_atom(Enc, Enc1),
  412    sgml_encoding_l(Enc1).
  413
  414sgml_encoding_l('iso-8859-1').
  415sgml_encoding_l('us-ascii').
  416sgml_encoding_l('utf-8').
  417sgml_encoding_l('utf8').
  418sgml_encoding_l('iso_latin_1').
  419sgml_encoding_l('ascii').
  420
  421load_structure_from_stream(In, Term, M:Options) :-
  422    (   select_option(dtd(DTD), Options, Options1)
  423    ->  ExplicitDTD = true
  424    ;   ExplicitDTD = false,
  425        Options1 = Options
  426    ),
  427    move_front(Options1, dialect(_), Options2), % dialect sets defaults
  428    setup_call_cleanup(
  429        new_sgml_parser(Parser,
  430                        [ dtd(DTD)
  431                        ]),
  432        parse(Parser, M:Options2, TermRead, In),
  433        free_sgml_parser(Parser)),
  434    (   ExplicitDTD == true
  435    ->  (   DTD = dtd(_, DocType),
  436            dtd_property(DTD, doctype(DocType))
  437        ->  true
  438        ;   true
  439        )
  440    ;   free_dtd(DTD)
  441    ),
  442    Term = TermRead.
  443
  444move_front(Options0, Opt, Options) :-
  445    selectchk(Opt, Options0, Options1),
  446    !,
  447    Options = [Opt|Options1].
  448move_front(Options, _, Options).
  449
  450
  451parse(Parser, M:Options, Document, In) :-
  452    set_parser_options(Options, Parser, In, Options1),
  453    parser_meta_options(Options1, M, Options2),
  454    set_input_location(Parser, In),
  455    sgml_parse(Parser,
  456               [ document(Document),
  457                 source(In)
  458               | Options2
  459               ]).
  460
  461set_parser_options([], _, _, []).
  462set_parser_options([H|T], Parser, In, Rest) :-
  463    (   set_parser_option(H, Parser, In)
  464    ->  set_parser_options(T, Parser, In, Rest)
  465    ;   Rest = [H|R2],
  466        set_parser_options(T, Parser, In, R2)
  467    ).
  468
  469set_parser_option(Var, _Parser, _In) :-
  470    var(Var),
  471    !,
  472    instantiation_error(Var).
  473set_parser_option(Option, Parser, _) :-
  474    def_entity(Option, Parser),
  475    !.
  476set_parser_option(offset(Offset), _Parser, In) :-
  477    !,
  478    seek(In, Offset, bof, _).
  479set_parser_option(Option, Parser, _In) :-
  480    parser_option(Option),
  481    !,
  482    set_sgml_parser(Parser, Option).
  483set_parser_option(Name=Value, Parser, In) :-
  484    Option =.. [Name,Value],
  485    set_parser_option(Option, Parser, In).
  486
  487
  488parser_option(dialect(_)).
  489parser_option(shorttag(_)).
  490parser_option(case_sensitive_attributes(_)).
  491parser_option(case_preserving_attributes(_)).
  492parser_option(system_entities(_)).
  493parser_option(max_memory(_)).
  494parser_option(file(_)).
  495parser_option(line(_)).
  496parser_option(space(_)).
  497parser_option(number(_)).
  498parser_option(defaults(_)).
  499parser_option(doctype(_)).
  500parser_option(qualify_attributes(_)).
  501parser_option(encoding(_)).
  502parser_option(keep_prefix(_)).
  503
  504
  505def_entity(entity(Name, Value), Parser) :-
  506    get_sgml_parser(Parser, dtd(DTD)),
  507    xml_quote_attribute(Value, QValue),
  508    setup_call_cleanup(open_dtd(DTD, [], Stream),
  509                       format(Stream, '<!ENTITY ~w "~w">~n',
  510                              [Name, QValue]),
  511                       close(Stream)).
  512def_entity(xmlns(URI), Parser) :-
  513    set_sgml_parser(Parser, xmlns(URI)).
  514def_entity(xmlns(NS, URI), Parser) :-
  515    set_sgml_parser(Parser, xmlns(NS, URI)).

 parser_meta_options(+Options0, +Module, -Options)

Qualify meta-calling options to the parser.

  521parser_meta_options([], _, []).
  522parser_meta_options([call(When, Closure)|T0], M, [call(When, M:Closure)|T]) :-
  523    !,
  524    parser_meta_options(T0, M, T).
  525parser_meta_options([H|T0], M, [H|T]) :-
  526    parser_meta_options(T0, M, T).

 set_input_location(+Parser, +In:stream) is det

Set the input location if this was not set explicitly

  533set_input_location(Parser, _In) :-
  534    get_sgml_parser(Parser, file(_)),
  535    !.
  536set_input_location(Parser, In) :-
  537    stream_property(In, file_name(File)),
  538    !,
  539    set_sgml_parser(Parser, file(File)),
  540    stream_property(In, position(Pos)),
  541    set_sgml_parser(Parser, position(Pos)).
  542set_input_location(_, _).
  543
  544                 /*******************************
  545                 *           UTILITIES          *
  546                 *******************************/

 load_sgml_file(+File, -DOM) is det

Load SGML from File and unify the resulting DOM structure with DOM.

deprecated

- New code should use load_sgml/3.

  555load_sgml_file(File, Term) :-
  556    load_sgml(File, Term, []).

 load_xml_file(+File, -DOM) is det

Load XML from File and unify the resulting DOM structure with DOM.

deprecated

- New code should use load_xml/3.

  565load_xml_file(File, Term) :-
  566    load_xml(File, Term, []).

 load_html_file(+File, -DOM) is det

Load HTML from File and unify the resulting DOM structure with DOM.

deprecated

- New code should use load_html/3.

  575load_html_file(File, DOM) :-
  576    load_html(File, DOM, []).

 load_html(+Input, -DOM, +Options) is det

Load HTML text from Input and unify the resulting DOM structure with DOM. Options are passed to load_structure/3, after adding the following default options:

dtd(DTD)

Pass the DTD for HTML as obtained using dtd(html, DTD).

dialect(Dialect)

Current dialect from the Prolog flag html_dialect

max_errors(-1)

syntax_errors(quiet)

Most HTML encountered in the wild contains errors. Even in the context of errors, the resulting DOM term is often a reasonable guess at the intent of the author.

You may also want to use the library(http/http_open) to support loading from HTTP and HTTPS URLs. For example:

:- use_module(library(http/http_open)).
:- use_module(library(sgml)).

load_html_url(URL, DOM) :-
    load_html(URL, DOM, []).

  605load_html(File, Term, M:Options) :-
  606    current_prolog_flag(html_dialect, Dialect),
  607    dtd(Dialect, DTD),
  608    merge_options(Options,
  609                  [ dtd(DTD),
  610                    dialect(Dialect),
  611                    max_errors(-1),
  612                    syntax_errors(quiet)
  613                  ], Options1),
  614    load_structure(File, Term, M:Options1).

 load_xml(+Input, -DOM, +Options) is det

Load XML text from Input and unify the resulting DOM structure with DOM. Options are passed to load_structure/3, after adding the following default options:

• dialect(xml)

  624load_xml(Input, DOM, M:Options) :-
  625    merge_options(Options,
  626                  [ dialect(xml)
  627                  ], Options1),
  628    load_structure(Input, DOM, M:Options1).

 load_sgml(+Input, -DOM, +Options) is det

Load SGML text from Input and unify the resulting DOM structure with DOM. Options are passed to load_structure/3, after adding the following default options:

• dialect(sgml)

  638load_sgml(Input, DOM, M:Options) :-
  639    merge_options(Options,
  640                  [ dialect(sgml)
  641                  ], Options1),
  642    load_structure(Input, DOM, M:Options1).
  643
  644
  645
  646                 /*******************************
  647                 *            ENCODING          *
  648                 *******************************/

 xml_quote_attribute(+In, -Quoted) is det

 xml_quote_cdata(+In, -Quoted) is det

Backward compatibility for versions that allow to specify encoding. All characters that cannot fit the encoding are mapped to XML character entities (&#dd;). Using ASCII is the safest value.

  658xml_quote_attribute(In, Quoted) :-
  659    xml_quote_attribute(In, Quoted, ascii).
  660
  661xml_quote_cdata(In, Quoted) :-
  662    xml_quote_cdata(In, Quoted, ascii).

 xml_name(+Atom) is semidet

True if Atom is a valid XML name.

  668xml_name(In) :-
  669    xml_name(In, ascii).
  670
  671
  672                 /*******************************
  673                 *    XML CHARACTER CLASSES     *
  674                 *******************************/

 xml_basechar(+CodeOrChar) is semidet

 xml_ideographic(+CodeOrChar) is semidet

 xml_combining_char(+CodeOrChar) is semidet

 xml_digit(+CodeOrChar) is semidet

 xml_extender(+CodeOrChar) is semidet

XML character classification predicates. Each of these predicates accept both a character (one-character atom) and a code (integer).

See also

- http://www.w3.org/TR/2006/REC-xml-20060816

  689                 /*******************************
  690                 *         TYPE CHECKING        *
  691                 *******************************/

 xml_is_dom(@Term) is semidet

True if term statisfies the structure as returned by load_structure/3 and friends.

  698xml_is_dom(0) :- !, fail.               % catch variables
  699xml_is_dom(List) :-
  700    is_list(List),
  701    !,
  702    xml_is_content_list(List).
  703xml_is_dom(Term) :-
  704    xml_is_element(Term).
  705
  706xml_is_content_list([]).
  707xml_is_content_list([H|T]) :-
  708    xml_is_content(H),
  709    xml_is_content_list(T).
  710
  711xml_is_content(0) :- !, fail.
  712xml_is_content(pi(Pi)) :-
  713    !,
  714    atom(Pi).
  715xml_is_content(CDATA) :-
  716    atom(CDATA),
  717    !.
  718xml_is_content(CDATA) :-
  719    string(CDATA),
  720    !.
  721xml_is_content(Term) :-
  722    xml_is_element(Term).
  723
  724xml_is_element(element(Name, Attributes, Content)) :-
  725    dom_name(Name),
  726    dom_attributes(Attributes),
  727    xml_is_content_list(Content).
  728
  729dom_name(NS:Local) :-
  730    atom(NS),
  731    atom(Local),
  732    !.
  733dom_name(Local) :-
  734    atom(Local).
  735
  736dom_attributes(0) :- !, fail.
  737dom_attributes([]).
  738dom_attributes([H|T]) :-
  739    dom_attribute(H),
  740    dom_attributes(T).
  741
  742dom_attribute(Name=Value) :-
  743    dom_name(Name),
  744    atomic(Value).
  745
  746
  747                 /*******************************
  748                 *            MESSAGES          *
  749                 *******************************/
  750:- multifile
  751    prolog:message/3.  752
  753%       Catch messages.  sgml/4 is generated by the SGML2PL binding.
  754
  755prolog:message(sgml(Parser, File, Line, Message)) -->
  756    { get_sgml_parser(Parser, dialect(Dialect))
  757    },
  758    [ 'SGML2PL(~w): ~w:~w: ~w'-[Dialect, File, Line, Message] ].
  759
  760
  761                 /*******************************
  762                 *         XREF SUPPORT         *
  763                 *******************************/
  764
  765:- multifile
  766    prolog:called_by/2.  767
  768prolog:called_by(sgml_parse(_, Options), Called) :-
  769    findall(Meta, meta_call_term(_, Meta, Options), Called).
  770
  771meta_call_term(T, G+N, Options) :-
  772    T = call(Event, G),
  773    pmember(T, Options),
  774    call_params(Event, Term),
  775    functor(Term, _, N).
  776
  777pmember(X, List) :-                     % member for partial lists
  778    nonvar(List),
  779    List = [H|T],
  780    (   X = H
  781    ;   pmember(X, T)
  782    ).
  783
  784call_params(begin, begin(tag,attributes,parser)).
  785call_params(end,   end(tag,parser)).
  786call_params(cdata, cdata(cdata,parser)).
  787call_params(pi,    pi(cdata,parser)).
  788call_params(decl,  decl(cdata,parser)).
  789call_params(error, error(severity,message,parser)).
  790call_params(xmlns, xmlns(namespace,url,parser)).
  791call_params(urlns, urlns(url,url,parser)).
  792
  793                 /*******************************
  794                 *           SANDBOX            *
  795                 *******************************/
  796
  797:- multifile
  798    sandbox:safe_primitive/1,
  799    sandbox:safe_meta_predicate/1.  800
  801sandbox:safe_meta_predicate(sgml:load_structure/3).
  802sandbox:safe_primitive(sgml:dtd(Dialect, _)) :-
  803    dtd_alias(Dialect, _).
  804sandbox:safe_primitive(sgml:xml_quote_attribute(_,_,_)).
  805sandbox:safe_primitive(sgml:xml_quote_cdata(_,_,_)).
  806sandbox:safe_primitive(sgml:xml_name(_,_)).
  807sandbox:safe_primitive(sgml:xml_basechar(_)).
  808sandbox:safe_primitive(sgml:xml_ideographic(_)).
  809sandbox:safe_primitive(sgml:xml_combining_char(_)).
  810sandbox:safe_primitive(sgml:xml_digit(_)).
  811sandbox:safe_primitive(sgml:xml_extender(_)).
  812sandbox:safe_primitive(sgml:iri_xml_namespace(_,_,_)).
  813sandbox:safe_primitive(sgml:xsd_number_string(_,_)).
  814sandbox:safe_primitive(sgml:xsd_time_string(_,_,_))