(text sxml *) libraries are the adaptation of Oleg Kiselyov's
SXML framework SSAX, which is based on S-expression representation of XML
structure.
SSAX is a parser part of SXML framework.
This is a quote from SSAX webpage:
The framework consists of a DOM/SXML parser, a SAX parser, and a supporting library of lexing and parsing procedures. The procedures in the package can be used separately to tokenize or parse various pieces of XML documents. The framework supports XML Namespaces, character, internal and external parsed entities, xml:space, attribute value normalization, processing instructions and CDATA sections. The package includes a semi-validating SXML parser: a DOM-mode parser that is an instantiation of a SAX parser (called SSAX). The parsing framework offers support for XML validation, to the full or any user-specified degree. Framework's procedures by themselves detect great many validation errors and almost all well-formedness errors. Furthermore, a user is given a chance to set his own handlers to capture the rest of the errors. Content is validated given user-specified constraints, which the user can derive from a DTD, from an XML schema, or from other competing doctype specification formats. SSAX is a full-featured, algorithmically optimal, pure-functional parser, which can act as a stream processor. SSAX is an efficient SAX parser that is easy to use. SSAX minimizes the amount of application-specific state that has to be shared among user-supplied event handlers. SSAX makes the maintenance of an application-specific element stack unnecessary, which eliminates several classes of common bugs. SSAX is written in a pure-functional subset of Scheme. Therefore, the event handlers are referentially transparent, which makes them easier for a programmer to write and to reason about. The more expressive, reliable and easier to use application interface for the event-driven XML parsing is the outcome of implementing the parsing engine as an enhanced tree fold combinator, which fully captures the control pattern of the depth-first tree traversal.
Sagittarius supports the latest version of SSAX 5.1.
All procedures and macros are described bottom up. So you might be interested only in user level APIs. If so, see Highest-level parsers: XML to SXML.
I derived the content of this part of the manual from SSAX source code, just by converting its comments into this manual format. The original text is by Oleg Kiselyov.
This is a package of low-to-high level lexing and parsing procedures that can be combined to yield a SAX, a DOM, a validating parsers, or a parser intended for a particular document type. The procedures in the package can be used separately to tokenize or parse various pieces of XML documents. The package supports XML Namespaces, internal and external parsed entities, user-controlled handling of whitespace, and validation. This module therefore is intended to be a framework, a set of "Lego blocks" you can use to build a parser following any discipline and performing validation to any degree. As an example of the parser construction, this file includes a semi-validating SXML parser.
The present XML framework has a "sequential" feel of SAX yet a "functional style" of DOM. Like a SAX parser, the framework scans the document only once and permits incremental processing. An application that handles document elements in order can run as efficiently as possible. Unlike a SAX parser, the framework does not require an application register stateful callbacks and surrender control to the parser. Rather, it is the application that can drive the framework -- calling its functions to get the current lexical or syntax element. These functions do not maintain or mutate any state save the input port. Therefore, the framework permits parsing of XML in a pure functional style, with the input port being a monad (or a linear, read-once parameter).
Besides the PORT, there is another monad -- SEED. Most of the middle- and high-level parsers are single-threaded through the seed. The functions of this framework do not process or affect the SEED in any way: they simply pass it around as an instance of an opaque datatype. User functions, on the other hand, can use the seed to maintain user's state, to accumulate parsing results, etc. A user can freely mix his own functions with those of the framework. On the other hand, the user may wish to instantiate a high-level parser: ssax:make-elem-parser or ssax:make-parser. In the latter case, the user must provide functions of specific signatures, which are called at predictable moments during the parsing: to handle character data, element data, or processing instructions (PI). The functions are always given the SEED, among other parameters, and must return the new SEED.
From a functional point of view, XML parsing is a combined pre-post-order traversal of a "tree" that is the XML document itself. This down-and-up traversal tells the user about an element when its start tag is encountered. The user is notified about the element once more, after all element's children have been handled. The process of XML parsing therefore is a fold over the raw XML document. Unlike a fold over trees defined in [1], the parser is necessarily single-threaded -- obviously as elements in a text XML document are laid down sequentially. The parser therefore is a tree fold that has been transformed to accept an accumulating parameter [1,2].
Formally, the denotational semantics of the parser can be expressed as
parser:: (Start-tag -> Seed -> Seed) ->
(Start-tag -> Seed -> Seed -> Seed) ->
(Char-Data -> Seed -> Seed) ->
XML-text-fragment -> Seed -> Seed
parser fdown fup fchar "<elem attrs> content </elem>" seed
= fup "<elem attrs>" seed
(parser fdown fup fchar "content" (fdown "<elem attrs>" seed))
parser fdown fup fchar "char-data content" seed
= parser fdown fup fchar "content" (fchar "char-data" seed)
parser fdown fup fchar "elem-content content" seed
= parser fdown fup fchar "content" (
parser fdown fup fchar "elem-content" seed)
Compare the last two equations with the left fold fold-left kons elem:list seed = fold-left kons list (kons elem seed)
The real parser created my ssax:make-parser is slightly more complicated, to account for processing instructions, entity references, namespaces, processing of document type declaration, etc.
The XML standard document referred to in this module is http://www.w3.org/TR/1998/REC-xml-19980210.htmlThe present file also defines a procedure that parses the text of an XML document or of a separate element into SXML, an S-expression-based model of an XML Information Set. SXML is also an Abstract Syntax Tree of an XML document. SXML is similar but not identical to DOM; SXML is particularly suitable for Scheme-based XML/HTML authoring, SXPath queries, and tree transformations. See SXML.html for more details. SXML is a term implementation of evaluation of the XML document [3]. The other implementation is context-passing.
The present frameworks fully supports the XML Namespaces Recommendation: http://www.w3.org/TR/REC-xml-names/Other links:
[1] Jeremy Gibbons, Geraint Jones, "The Under-appreciated Unfold," Proc. ICFP'98, 1998, pp. 273-279.
[2] Richard S. Bird, The promotion and accumulation strategies in transformational programming, ACM Trans. Progr. Lang. Systems, 6(4):487-504, October 1984.
[3] Ralf Hinze, "Deriving Backtracking Monad Transformers," Functional Pearl. Proc ICFP'00, pp. 186-197.
a symbol START, END, PI, DECL, COMMENT,
CDSECT or ENTITY-REF that identifies a markup token
a name (called GI in the XML Recommendation) as given in an xml document for a markup token: start-tag, PI target, attribute name. If a GI is an NCName, UNRES-NAME is this NCName converted into a Scheme symbol. If a GI is a QName, UNRES-NAME is a pair of symbols: (PREFIX . LOCALPART)
An expanded name, a resolved version of an UNRES-NAME. For an element or an attribute name with a non-empty namespace URI, RES-NAME is a pair of symbols, (URI-SYMB . LOCALPART). Otherwise, it's a single symbol.
A symbol: ANY
anything goes, expect an END tag. EMPTY-TAG
no content, and no END-tag is coming EMPTY
no content, expect the END-tag as the next token PCDATA
expect character data only, and no children elements MIXED
ELEM-CONTENT
A symbol representing a namespace URI -- or other symbol chosen by the user to represent URI. In the former case, URI-SYMB is created by %-quoting of bad URI characters and converting the resulting string into a symbol.
A list representing namespaces in effect. An element of the list has one of the following forms:
(PREFIX URI-SYMB . URI-SYMB)(PREFIX USER-PREFIX . URI-SYMB) USER-PREFIX is a symbol chosen by the user to represent the URI.
(#f USER-PREFIX . URI-SYMB)
Specification of the user-chosen prefix and a URI-SYMBOL. (*DEFAULT* USER-PREFIX . URI-SYMB)
Declaration of the default namespace (*DEFAULT* #f . #f)
Un-declaration of the default namespace. This notation represents overriding of the previous declaration A NAMESPACES list may contain several elements for the same PREFIX. The one closest to the beginning of the list takes effect.
An ordered collection of (NAME . VALUE) pairs, where NAME is a RES-NAME or an UNRES-NAME. The collection is an ADT
A procedure of three arguments: STRING1 STRING2 SEED returning a new SEED The procedure is supposed to handle a chunk of character data STRING1 followed by a chunk of character data STRING2. STRING2 is a short string, often "\n" and even ""
An assoc list of pairs:
(named-entity-name . named-entity-body)a record This record represents a markup, which is, according to the XML Recommendation, "takes the form of start-tags, end-tags, empty-element tags, entity references, character references, comments, CDATA section delimiters, document type declarations, and processing instructions." kind
a TAG-KIND head
an UNRES-NAME. For xml-tokens of kinds 'COMMENT and 'CDSECT, the head is #f For example,
<P> => kind='START, head='P
</P> => kind='END, head='P
<BR/> => kind='EMPTY-EL, head='BR
<!DOCTYPE OMF ...> => kind='DECL, head='DOCTYPE
<?xml version="1.0"?> => kind='PI, head='xml
&my-ent; => kind = 'ENTITY-REF, head='my-ent
Character references are not represented by xml-tokens as these references are transparently resolved into the corresponding characters.
a record The record represents a datatype of an XML document: the list of declared elements and their attributes, declared notations, list of replacement strings or loading procedures for parsed general entities, etc. Normally an xml-decl record is created from a DTD or an XML Schema, although it can be created and filled in in many other ways (e.g., loaded from a file). elems
an (assoc) list of decl-elem or #f. The latter instructs the parser to do no validation of elements and attributes. decl-elem
declaration of one element:
(_elem-name_ _elem-content_ _decl-attrs_)an element of an ATTLIST, declaration of one attribute
(_attr-name_ _content-type_ _use-type_ _default-value_)A constructor and a predicate for a XML-TOKEN record.
Accessor macros of a XML-TOKEN record.
They deal with primitive lexical units (Names, whitespaces, tags) and with pieces of more generic productions. Most of these parsers must be called in appropriate context. For example, ssax:complete-start-tag must be called only when the start-tag has been detected and its GI has been read.
Skip the S (whitespace) production as defined by
[3] S ::= (#x20 | #x9 | #xD | #xA)The procedure returns the first not-whitespace character it encounters while scanning the port. This character is left on the input stream.
Read a Name lexem and return it as string
[4] NameChar ::= Letter | Digit | '.' | '-' | '_' | ':'
| CombiningChar | Extender
[5] Name ::= (Letter | '_' | ':') (NameChar)*
This code supports the XML Namespace Recommendation REC-xml-names, which modifies the above productions as follows:
[4] NCNameChar ::= Letter | Digit | '.' | '-' | '_'
| CombiningChar | Extender
[5] NCName ::= (Letter | '_') (NCNameChar)*
As the Rec-xml-names says, "An XML document conforms to this specification if all other tokens [other than element types and attribute names] in the document which are required, for XML conformance, to match the XML production for Name, match this specification's production for NCName." Element types and attribute names must match the production QName, defined below.
Read a NCName starting from the current position in the port and preturn it as a symbol.
Read a (namespace-) Qualified Name, QName, from the current position in the port.
From REC-xml-names:
[6] QName ::= (Prefix ':')? LocalPart
[7] Prefix ::= NCName
[8] LocalPart ::= NCName
Return: an UNRES-NAME
The prefix of the pre-defined XML namespace
Compare one RES-NAME or an UNRES-NAME with the other. Return a symbol '<, '>, or '= depending on the result of the comparison. Names without PREFIX are always smaller than those with the PREFIX.
An UNRES-NAME that is postulated to be larger than anything that can occur in a well-formed XML document. name-compare enforces this postulate.
This procedure starts parsing of a markup token. The current position in the stream must be #\<. This procedure scans enough of the input stream to figure out what kind of a markup token it is seeing. The procedure returns an xml-token structure describing the token. Note, generally reading of the current markup is not finished! In particular, no attributes of the start-tag token are scanned.
Here's a detailed break out of the return values and the position in the _port_when that particular value is returned:
only PI-target is read. To finish the Processing Instruction and disregard it, call ssax:skip-pi. ssax:read-attributes may be useful as well (for PIs whose content is attribute-value pairs)
The end tag is read completely; the current position is right after the terminating #\> character.
is read and skipped completely. The current position is right after "-->" that terminates the comment.
The current position is right after "<!CDATA[" Use ssax:read-cdata-body to read the rest.
We have read the keyword (the one that follows "<!") identifying this declaration markup. The current position is after the keyword (usually a whitespace character)
We have read the keyword (GI) of this start tag. No attributes are scanned yet. We don't know if this tag has an empty content either. Use ssax:complete-start-tag to finish parsing of the token.
The current position is inside a PI. Skip till the rest of the PI
The current position is right after reading the PITarget. We read the body of PI and return is as a string. The port will point to the character right after '?>' combination that terminates PI.
[16] PI ::= '<?' PITarget (S (Char* - (Char* '?>' Char*)))? '?>'The current pos in the port is inside an internal DTD subset (e.g., after reading #\[ that begins an internal DTD subset) Skip until the "]>" combination that terminates this DTD
This procedure must be called after we have read a string "<![CDATA[" that begins a CDATA section. The current position must be the first position of the CDATA body. This function reads lines of the CDATA body and passes them to a STR-HANDLER, a character data consumer.
The str-handler is a STR-HANDLER, a procedure STRING1 STRING2 SEED.
The first STRING1 argument to STR-HANDLER never contains a newline.
The second STRING2 argument often will. On the first invocation of
the STR-HANDLER, the seed is the one passed to ssax:read-cdata-bodyas the third argument. The result of this first invocation will be
passed as the seed argument to the second invocation of the line
consumer, and so on. The result of the last invocation of the
STR-HANDLER is returned by the ssax:read-cdata-body. Note a
similarity to the fundamental 'fold' iterator.
Within a CDATA section all characters are taken at their face value, with only three exceptions:
CR, LF, and CRLF are treated as line delimiters, and passed
as a single #\newline to the STR-HANDLER
"]]>" combination is the end of the CDATA section.
> is treated as an embedded #\> character
Note, < and & are not specially recognized (and are not expanded)!
[66] CharRef ::= '&#' [0-9]+ ';'
| '&#x' [0-9a-fA-F]+ ';'
This procedure must be called after we we have read "&#" that introduces a char reference. The procedure reads this reference and returns the corresponding char The current position in port will be after ";" that terminates the char reference Faults detected:
XML-Spec.html#wf-Legalchar
According to Section "4.1 Character and Entity References" of the XML Recommendation:
"[Definition: A character reference refers to a specific character in the ISO/IEC 10646 character set, for example one not directly accessible from available input devices.]"
Therefore, we use a ucscode->char function to convert a character code into the character -- *regardless* of the current character encoding of the input stream.
Expand and handle a parsed-entity reference
port - a PORT
name - the name of the parsed entity to expand, a symbol
entities - see ENTITIES
content-handler -- procedure PORT ENTITIES SEED that is supposed to return a SEED
str-handler - a STR-HANDLER. It is called if the entity in question turns out to be a pre-declared entity
The result is the one returned by CONTENT-HANDLER or STR-HANDLER Faults detected:
XML-Spec.html#wf-entdeclared
XML-Spec.html#norecursion
Utility procedures to deal with attribute list, which keeps name-value association.
This procedure reads and parses a production Attribute*
[41] Attribute ::= Name Eq AttValue
[10] AttValue ::= '"' ([^<&"] | Reference)* '"'
| "'" ([^<&'] | Reference)* "'"
[25] Eq ::= S? '=' S?
The procedure returns an ATTLIST, of Name (as UNRES-NAME), Value (as string) pairs. The current character on the PORT is a non-whitespace character that is not an ncname-starting character.
Note the following rules to keep in mind when reading an 'AttValue' "Before the value of an attribute is passed to the application or checked for validity, the XML processor must normalize it as follows:
a character reference is processed by appending the referenced character to the attribute value
an entity reference is processed by recursively processing the replacement text of the entity [see ENTITIES] [named entities amp lt gt quot apos are assumed pre-declared]
a whitespace character (#x20, #xD, #xA, #x9) is processed by appending #x20 to the normalized value, except that only a single #x20 is appended for a "#xD#xA" sequence that is part of an external parsed entity or the literal entity value of an internal parsed entity
other characters are processed by appending them to the normalized value
"
Faults detected:
XML-Spec.html#CleanAttrVals
XML-Spec.html#uniqattspec
Convert an UNRES-NAME to a RES-NAME given the appropriate NAMESPACES declarations. the last parameter apply-default-ns? determines if the default namespace applies (for instance, it does not for attribute names)
Per REC-xml-names/#nsc-NSDeclared, "xml" prefix is considered pre-declared and bound to the namespace name "http://www.w3.org/XML/1998/namespace".
This procedure tests for the namespace constraints: http://www.w3.org/TR/REC-xml-names/#nsc-NSDeclared
Convert a URI-STR to an appropriate symbol
This procedure is to complete parsing of a start-tag markup. The procedure must be called after the start tag token has been read. TAG is an UNRES-NAME. ELEMS is an instance of xml-decl::elems; it can be #f to tell the function to do no validation of elements and their attributes.
This procedure returns several values:
a RES-NAME.
element's attributes, an ATTLIST of (RES-NAME . STRING) pairs. The list does NOT include xmlns attributes.
the input list of namespaces amended with namespace (re-)declarations contained within the start-tag under parsing
On exit, the current position in PORT will be the first character after #\> that terminates the start-tag markup.
Faults detected:
XML-Spec.html#enum
XML-Spec.html#RequiredAttr
XML-Spec.html#FixedAttr
XML-Spec.html#ValueType
XML-Spec.html#uniqattspec (after namespaces prefixes are resolved)
XML-Spec.html#elementvalid
REC-xml-names/#dt-NSName
Note, although XML Recommendation does not explicitly say it, xmlns and xmlns: attributes don't have to be declared (although they can be declared, to specify their default value)
This procedure parses an ExternalID production:
[75] ExternalID ::= 'SYSTEM' S SystemLiteral
| 'PUBLIC' S PubidLiteral S SystemLiteral
[11] SystemLiteral ::= ('"' [^"]* '"') | ("'" [^']* "'")
[12] PubidLiteral ::= '"' PubidChar* '"' | "'" (PubidChar - "'")* "'"
[13] PubidChar ::= #x20 | #xD | #xA | [a-zA-Z0-9]
| [-'()+,./:=?;!*#@$_%]
This procedure is supposed to be called when an ExternalID is expected; that is, the current character must be either #\S or #\P that start correspondingly a SYSTEM or PUBLIC token. This procedure returns the SystemLiteral as a string. A PubidLiteral is disregarded if present.
They parse productions corresponding to the whole (document) entity or its higher-level pieces (prolog, root element, etc).
Scan the Misc production in the context
[1] document ::= prolog element Misc*
[22] prolog ::= XMLDecl? Misc* (doctypedec l Misc*)?
[27] Misc ::= Comment | PI | S
The following function should be called in the prolog or epilog contexts. In these contexts, whitespaces are completely ignored. The return value from ssax:scan-Misc is either a PI-token, a DECL-token, a START token, or EOF. Comments are ignored and not reported.
This procedure is to read the character content of an XML document or an XML element.
[43] content ::=
(element | CharData | Reference | CDSect | PI
| Comment)*
To be more precise, the procedure reads CharData, expands CDSect and character entities, and skips comments. The procedure stops at a named reference, EOF, at the beginning of a PI or a start/end tag.
a PORT to read
a boolean indicating if EOF is normal, i.e., the character data may be terminated by the EOF. EOF is normal while processing a parsed entity.
a STR-HANDLER
an argument passed to the first invocation of STR-HANDLER.
The procedure returns two results: SEED and TOKEN. The SEED is the result of the last invocation of STR-HANDLER, or the original seed if STR-HANDLER was never called.
TOKEN can be either an eof-object (this can happen only if expect-eof? was #t), or:
an xml-token describing a START tag or an END-tag; For a start token, the caller has to finish reading it.
an xml-token describing the beginning of a PI. It's up to an application to read or skip through the rest of this PI;
an xml-token describing a named entity reference.
CDATA sections and character references are expanded inline and never returned. Comments are silently disregarded.
As the XML Recommendation requires, all whitespace in character data must be preserved. However, a CR character (#xD) must be disregarded if it appears before a LF character (#xA), or replaced by a #xA character otherwise. See Secs. 2.10 and 2.11 of the XML Recommendation. See also the canonical XML Recommendation.
Make sure that TOKEN is of anticipated KIND and has anticipated GI Note GI argument may actually be a pair of two symbols, Namespace URI or the prefix, and of the localname. If the assertion fails, error-cont is evaluated by passing it three arguments: token kind gi. The result of error-cont is returned.
These parsers are a set of syntactic forms to instantiate a SSAX parser. A user can instantiate the parser to do the full validation, or no validation, or any particular validation. The user specifies which PI he wants to be notified about. The user tells what to do with the parsed character and element data. The latter handlers determine if the parsing follows a SAX or a DOM model.
Create a parser to parse and process one Processing Element (PI).
An assoc list of pairs (PI-TAG . PI-HANDLER) where PI-TAG is an NCName symbol, the PI target, and PI-HANDLER is a procedure PORT PI-TAG SEED where PORT points to the first symbol after the PI target. The handler should read the rest of the PI up to and including the combination '?>' that terminates the PI. The handler should return a new seed. One of the PI-TAGs may be the symbol *DEFAULT*. The corresponding handler will handle PIs that no other handler will. If the *DEFAULT* PI-TAG is not specified, ssax:make-pi-parser will assume the default handler that skips the body of the PI
The output of the ssax:make-pi-parser is a
``procedure _PORT_ _PI-TAG_ _SEED_``
that will parse the current PI according to the user-specified handlers.
Create a parser to parse and process one element, including its character content or children elements. The parser is typically applied to the root element of a document.
procedure ELEM-GI ATTRIBUTES NAMESPACES EXPECTED-CONTENT SEED where ELEM-GI is a RES-NAME of the element about to be processed. This procedure is to generate the seed to be passed to handlers that process the content of the element. This is the function identified as 'fdown' in the denotational semantics of the XML parser given in the title comments to this file.
procedure ELEM-GI ATTRIBUTES NAMESPACES PARENT-SEED SEED This procedure is called when parsing of ELEM-GI is finished. The SEED is the result from the last content parser (or from my-new-level-seed if the element has the empty content). PARENT-SEED is the same seed as was passed to my-new-level-seed. The procedure is to generate a seed that will be the result of the element parser. This is the function identified as 'fup' in the denotational semantics of the XML parser given in the title comments to this file.
A STR-HANDLER
See ssax:make-pi-handler above
The generated parser is a
procedure _START-TAG-HEAD_ _PORT_ _ELEMS_ _ENTITIES_ _NAMESPACES_ _PRESERVE-WS?_ _SEED_The procedure must be called after the start tag token has been
read. START-TAG-HEAD is an UNRES-NAME from the start-element tag.
ELEMS is an instance of xml-decl::elems.
See ssax:complete-start-tag::preserve-ws?Faults detected:
XML-Spec.html#elementvalid
XML-Spec.html#GIMatch
Create an XML parser, an instance of the XML parsing framework. This will be a SAX, a DOM, or a specialized parser depending on the supplied user-handlers.
user-handler-tag is a symbol that identifies a procedural expression that follows the tag. Given below are tags and signatures of the corresponding procedures. Not all tags have to be specified. If some are omitted, reasonable defaults will apply.
If internal-subset? is #t, the current position in the port is right after we have read #\[ that begins the internal DTD subset. We must finish reading of this subset before we return (or must call skip-internal-subset if we aren't interested in reading it). The port at exit must be at the first symbol after the whole DOCTYPE declaration. The handler-procedure must generate four values: ELEMS ENTITIES NAMESPACES SEED See xml-decl::elems for ELEMS. It may be #f to switch off the validation. NAMESPACES will typically contain USER-PREFIXes for selected URI-SYMBs. The default handler-procedure skips the internal subset, if any, and returns (values #f '() '() seed)
where ELEM-GI is an UNRES-NAME of the root element. This procedure is called when an XML document under parsing contains no DOCTYPE declaration. The handler-procedure, as a DOCTYPE handler procedure above, must generate four values: ELEMS ENTITIES NAMESPACES SEED The default handler-procedure returns (values #f '() '() seed)
where ELEM-GI is an UNRES-NAME of the root element. This procedure is called when an XML document under parsing does contains the DOCTYPE declaration. The handler-procedure must generate a new SEED (and verify that the name of the root element matches the doctype, if the handler so wishes). The default handler-procedure is the identity function.
see ssax:make-elem-parser, my-new-level-seed
see ssax:make-elem-parser, my-finish-element
see ssax:make-elem-parser, my-char-data-handler
see ssax:make-pi-parserThe default value is '()
The generated parser is a
procedure PORT SEED
This procedure parses the document prolog and then exits to
an element parser (created by ssax:make-elem-parser) to handle
the rest.
[1] document ::= prolog element Misc*
[22] prolog ::= XMLDecl? Misc* (doctypedec | Misc*)?
[27] Misc ::= Comment | PI | S
[28] doctypedecl ::= '<!DOCTYPE' S Name (S ExternalID)? S?
('[' (markupdecl | PEReference | S)* ']' S?)? '>'
[29] markupdecl ::= elementdecl | AttlistDecl
| EntityDecl
| NotationDecl | PI
| Comment
First, a few utility procedures that turned out useful
given the list of fragments (some of which are text strings) reverse the list and concatenate adjacent text strings. We can prove from the general case below that if LIST-OF-FRAGS has zero or one element, the result of the procedure is equal? to its argument. This fact justifies the shortcut evaluation below.
given the list of fragments (some of which are text strings)
reverse the list and concatenate adjacent text strings.
We also drop "unsignificant" whitespace, that is, whitespace
in front, behind and between elements. The whitespace that
is included in character data is not affected.
We use this procedure to "intelligently" drop "insignificant"
whitespace in the parsed SXML. If the strict compliance with
the XML Recommendation regarding the whitespace is desired, please
use the ssax:reverse-collect-str procedure instead.
This is an instance of a SSAX parser above that returns an SXML representation of the XML document to be read from PORT. NAMESPACE-PREFIX-ASSIG is a list of (USER-PREFIX . URI-STRING) that assigns USER-PREFIXes to certain namespaces identified by particular URI-STRINGs. It may be an empty list. The procedure returns an SXML tree. The port points out to the first character after the root element.