\r\nThis code creates and accepts character lists rather than ECLiPSe strings. \r\nTo convert between character lists and (UTF8 or ASCII) strings, use the\r\nECLiPSe built-in string_list/3. For example, to parse a UTF-8 encoded\r\nXML file, use the following code:\r\n
\r\nxml_parse_file(File, Document) :-\r\n\topen(File, read, Stream),\r\n\tread_string(Stream, end_of_file, _, Utf8String),\r\n\tclose(Stream),\r\n\tstring_list(Utf8String, Chars, utf8),\r\n\txml_parse(Chars, Document).\r\n
\r\nMost of the subsequent text is taken literally from\r\n\r\nhttp://www.john.fletcher.dial.pipex.com/xml.pl.shtml.\r\n
\r\n\r\n\r\n\r\nThis program is offered free of charge, as unsupported source code. You may\r\nuse it, copy it, distribute it, modify it or sell it without restriction. \r\n
\r\nWe hope that it will be useful to you, but it is provided \"as is\" without\r\nany warranty express or implied, including but not limited to the warranty\r\nof non-infringement and the implied warranties of merchantability and fitness\r\nfor a particular purpose.\r\n
\r\nBinding Time Limited will not be liable for any damages suffered by you as\r\na result of using the Program. In no event will Binding Time Limited be\r\nliable for any special, indirect or consequential damages or lost profits\r\neven if Binding Time Limited has been advised of the possibility of their\r\noccurrence. Binding Time Limited will not be liable for any third party\r\nclaims against you.\r\n
\r\n\r\nHistory:\r\n$Log: xml_comments.ecl,v $\nRevision 1.1 2003/03/31 13:58:02 js10\nUpgraded to latest version from John Fletcher's web site\n\r\nRevision 1.2 2002/03/26 22:56:55 js10\r\nAdded John Fletcher's public domain XML parser/generator\r\n\r\nRevision 1.1 2002/03/26 22:50:07 js10\r\nAdded John Fletcher's public domain XML parser/generator\r\n\r\nRevision 1.1 2002-01-31 21:04:45+00 john\r\nUpdated Copyright statements.\r\n\r\nRevision 1.0 2001-10-17 20:46:24+01 john\r\nInitial revision\r\n\r\n\r\n
xml.pl is a module for parsing \r\nXML with Prolog, which provides Prolog applications with a simple\r\ninterface to XML documents. We have used it successfully in a number of\r\napplications.
\r\nIt supports a subset of XML suitable for XML Data and Worldwide Web\r\n applications. It is neither as strict nor as comprehensive as the XML 1.0 Specification\r\nmandates.
\r\nIt is not as strict, because, while the specification must eliminate\r\nambiguities, not all errors need to be regarded as faults, and some reasonable\r\nexamples of real XML usage would have to be rejected if they were.
\r\nIt is not as comprehensive, because, where the XML specification makes\r\n provision for more or less complete DTDs to be provided as part of a\r\ndocument, xml.pl supports the local definition of ENTITIES only.
\r\nWe have placed the code, and a small Windows\r\napplication which embodies it, into the public domain, to encourage the use\r\nof Prolog with XML.
\r\nWe hope that they will be useful to you, but they are not supported, and\r\nBinding Time Limited accept NO LIABILITY WHATSOEVER in respect of their\r\nuse.
\r\nThree predicates are exported by the module: xml_parse/[2,3], xml_subterm/2\r\nand xml_pp/1.
\r\nxml_parse( {+Controls}, +?Chars, ?+Document ) parses \r\nChars, a list of character codes, to/from a data structure of the form\r\n\r\nxml(<attributes>, <content>)\r\n , where:
<attributes> is a list of \r\n <name>=<data>\r\n attributes from the (possibly implicit) XML signature of the\r\ndocument.
<content> is a (possibly empty) list comprising occurrences of :
pcdata(<data>) | \r\n Text | \r\n
comment(<string>) | \r\n An xml comment; | \r\n
namespace(<URI>,<prefix>,<element>) | \r\n a Namespace | \r\n
element(<tag>, <attributes>, <content>) | \r\n <tag>..</tag> encloses <content> or <tag /> if empty | \r\n
instructions(<name>, <data>) | \r\n A PI <? <name> <data> ?> | \r\n
cdata(<data>) | \r\n <![CDATA[ <string> ]]> | \r\n
doctype(<tag>, <doctype id>) | \r\n DTD <!DOCTYPE .. > | \r\n
| \r\n | |
The conversions are not completely symmetrical, in that weaker XML is\r\naccepted than can be generated. Specifically, in-bound (Chars ->\r\nDocument) parsing does not require strictly well-formed XML. If \r\nChars does not represent well-formed XML, Document is\r\ninstantiated to the term | \r\n |
| \r\n | |
The | \r\n |
| \r\n | |
unparsed( <string> ) | \r\n Text which has not been parsed | \r\n
out_of_context( <tag> ) | \r\n <tag> is not closed | \r\n
in addition to the parsed term types. Out-bound (Document -> Chars) parsing does require that\r\nDocument defines well-formed XML. If an error is detected a 'domain'\r\nexception is raised. The domain exception will attempt to identify the particular sub-term in\r\nerror and the message will show a list of its ancestor elements in the form\r\n At this release, the Controls applying to in-bound (Chars ->\r\nDocument) parsing are: | \r\n |
| \r\n | |
extended_characters(<bool>) | \r\n Use the extended character entities for XHTML (default true) | \r\n
format(<bool>) | \r\n Strip layouts when no non-layout character data appears between elements. default\r\ntrue) | \r\n
For out-bound (Document -> Chars) parsing, the only available\r\noption is: | \r\n |
| \r\n | |
format(<bool>) | \r\n Indent the element content, (default true) | \r\n
| \r\n | |
Types | \r\n |
<tag> | \r\n An atom naming an element | \r\n
<data> | \r\n A "string" | \r\n
<name> | \r\n An atom, not naming an element | \r\n
<URI> | \r\n An atom giving the URI of a Namespace | \r\n
<string> | \r\n A "string": list of character codes. | \r\n
<doctype id> | \r\n one of public(<string>, <string>), system(<string>) or local | \r\n
<bool> | \r\n one of 'true' or 'false' | \r\n
xml_subterm( +XMLTerm, ?Subterm ) unifies Subterm with\r\na sub-term of Term. This can be especially useful when trying to\r\ntest or retrieve a deeply-nested subterm from a document. Note that \r\nXMLTerm is a sub-term of itself.
\r\nxml_pp( +XMLDocument )"pretty prints" XMLDocument on\r\nthe current output stream.
\r\nThe xml/2 data structure has some useful properties.
\r\nUsing an "abstract" Prolog representation of XML, in which terms represent\r\ndocument "nodes", makes the parser reuseable for any XML application.
\r\nIn effect, xml.pl encapsulates the application-independent tasks of document\r\nparsing and generation, which is essential where documents have components\r\nfrom more than one Namespace.
\r\nThe Prolog term representing a document has the same structure as the\r\ndocument itself, which makes the correspondence between the literal\r\nrepresentation of the Prolog term and the XML source readily apparent.
\r\nFor example, this simple SVG image:
\r\n<?xml version="1.0" standalone="no"?>\r\n<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/.../svg10.dtd"\r\n [\r\n <!ENTITY redblue "fill: red; stroke: blue; stroke-width: 1">\r\n ]>\r\n<svg xmlns="http://www.w3.org/2000/svg" width="500" height="500">\r\n <circle cx=" 25 " cy=" 25 " r=" 24 " style="&redblue;"/>\r\n</svg>\r\n
... translates into this Prolog term:
\r\nxml( [version="1.0", standalone="no"],\r\n [\r\n doctype( svg, public( "-//W3C//DTD SVG 1.0//EN", "http://www.w3.org/.../svg10.dtd" ) ),\r\n namespace( 'http://www.w3.org/2000/svg', "",\r\n element( svg,\r\n [width="500", height="500"],\r\n [\r\n element( circle,\r\n [cx="25", cy="25", r="24", style="fill: red; stroke: blue; stroke-width: 1"],\r\n [] )\r\n ] )\r\n )\r\n ] ).\r\n
Each type of node in an XML document is represented by a different Prolog\r\nfunctor, while data, (PCDATA, CDATA and Attribute Values), are left as\r\n"strings", (lists of character codes).
\r\nThe use of distinct functors for mark-up structures enables the efficient\r\nrecursive traversal of a document, while leaving the data as strings\r\nfacilitates application specific parsing of data content (aka \r\nMicro-parsing).
\r\nFor example, to turn every CDATA node into a PCDATA node with tabs expanded\r\ninto spaces:
\r\n\r\ncdata_to_pcdata( cdata(CharsWithTabs), pcdata(CharsWithSpaces) ) :-\r\n tab_expansion( CharsWithTabs, CharsWithSpaces ).\r\ncdata_to_pcdata( xml(Attributes, Content1), xml(Attributes, Content2) ) :-\r\n cdata_to_pcdata( Content1, Content2 ).\r\ncdata_to_pcdata( namespace(URI,Prefix,Content1), namespace(URI,Prefix,Content2) ) :-\r\n cdata_to_pcdata( Content1, Content2 ).\r\ncdata_to_pcdata( element(Name,Attrs,Content1), element(Name,Attrs,Content2) ) :-\r\n cdata_to_pcdata( Content1, Content2 ).\r\ncdata_to_pcdata( [], [] ).\r\ncdata_to_pcdata( [H1|T1], [H2|T2] ) :-\r\n cdata_to_pcdata( H1, H2 ),\r\n cdata_to_pcdata( T1, T2 ).\r\ncdata_to_pcdata( pcdata(Chars), pcdata(Chars) ).\r\ncdata_to_pcdata( comment(Chars), comment(Chars) ).\r\ncdata_to_pcdata( instructions(Name, Chars), instructions(Name, Chars) ).\r\ncdata_to_pcdata( doctype(Tag, DoctypeId), doctype(Tag, DoctypeId) ).\r\n\r\n
The above uses no 'cuts', but will not create any choice points with ground\r\ninput.
\r\nThe resolution of entity references and the decomposition of the document\r\ninto distinct nodes means that the calling application is not concerned with\r\nthe occasionally messy syntax of XML documents.
\r\nFor example, the clean separation of namespace nodes means that Namespaces,\r\nwhich are useful in combining specifications developed separately, have similar\r\nusefulness in combining applications developed separately.
\r\nThe source code is available here. Although\r\nit is unsupported, please feel free to \r\ne-mail queries and suggestions. We will respond as time allows.
\r\n")). :- comment(xml_parse / 2, [summary : "Parse or generate XML documents", amode : xml_parse(+, -), amode : xml_parse(-, +), args : ["Chars" : "List of characters", "Document" : "Document as structured term"], see_also : [xml_parse / 3, xml_subterm / 2, xml_pp / 1]]). :- comment(xml_parse / 3, [summary : "Parse or generate XML documents", amode : xml_parse(+, +, -), amode : xml_parse(+, -, +), args : ["Controls" : "List of options", "Chars" : "List of characters (XML text)", "Document" : "Document as structured term"], see_also : [xml_parse / 2], desc : ascii("\r\nxml_parse( {+Controls}, +?Chars, ?+Document ) parses Chars to/from a data\r\nstructure of the form xml(