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diff --git a/libjava/classpath/gnu/xml/aelfred2/package.html b/libjava/classpath/gnu/xml/aelfred2/package.html deleted file mode 100644 index e204258..0000000 --- a/libjava/classpath/gnu/xml/aelfred2/package.html +++ /dev/null @@ -1,506 +0,0 @@ -<!DOCTYPE html PUBLIC - '-//W3C//DTD XHTML 1.0 Transitional//EN' - 'http://www.w3.org/TR/xhtml1/DTD/transitional.dtd'> - -<html><head> - <title>package overview</title> -<!-- -/* - * Copyright (C) 1999,2000,2001 The Free Software Foundation, Inc. - */ ---> -</head><body> - -<p> This package contains Ælfred2, which includes an -enhanced SAX2-compatible version of the Ælfred -non-validating XML parser, a modular (and hence optional) -DTD validating parser, and modular (and hence optional) -JAXP glue to those. -Use these like any other SAX2 parsers. </p> - -<ul> - <li><a href="#about">About Ælfred</a><ul> - <li><a href="#principles">Design Principles</a></li> - <li><a href="#name">About the Name Ælfred</a></li> - <li><a href="#encodings">Character Encodings</a></li> - <li><a href="#violations">Known Conformance Violations</a></li> - <li><a href="#copyright">Licensing</a></li> - </ul></li> - - <li><a href="#changes">Changes Since the Last Microstar Release</a><ul> - <li><a href="#sax2">SAX2 Support</a></li> - <li><a href="#validation">Validation</a></li> - <li><a href="#smaller">You Want Smaller?</a></li> - <li><a href="#bugfixes">Bugs Fixed</a></li> - </ul></li> - -</ul> - -<h2><a name="about">About Ælfred</a></h2> - -<p>Ælfred is a XML parser written in the java programming language. - -<h3><a name="principles">Design Principles</a></h3> - -<p>In most Java applets and applications, XML should not be the central -feature; instead, XML is the means to another end, such as loading -configuration information, reading meta-data, or parsing transactions.</p> - -<p> When an XML parser is only a single component of a much larger -program, it cannot be large, slow, or resource-intensive. With Java -applets, in particular, code size is a significant issue. The standard -modem is still not operating at 56 Kbaud, or sometimes even with data -compression. Assuming an uncompressed 28.8 Kbaud modem, only about -3 KBytes can be downloaded in one second; compression often doubles -that speed, but a V.90 modem may not provide another doubling. When -used with embedded processors, similar size concerns apply. </p> - -<p> Ælfred is designed for easy and efficient use over the Internet, -based on the following principles: </p> <ol> - -<li> Ælfred must be as small as possible, so that it doesn't add too - much to an applet's download time. </li> - -<li> Ælfred must use as few class files as possible, to minimize the - number of HTTP connections necessary. (The use of JAR files has made this - be less of a concern.) </li> - -<li> Ælfred must be compatible with most or all Java implementations - and platforms. (Write once, run anywhere.) </li> - -<li> Ælfred must use as little memory as possible, so that it does - not take away resources from the rest of your program. (It doesn't force - you to use DOM or a similar costly data structure API.)</li> - -<li> Ælfred must run as fast as possible, so that it does not slow down - the rest of your program. </li> - -<li> Ælfred must produce correct output for well-formed and valid - documents, but need not reject every document that is not valid or - not well-formed. (In Ælfred2, correctness was a bigger concern - than in the original version; and a validation option is available.) </li> - -<li> Ælfred must provide full internationalization from the first - release. (Ælfred2 now automatically handles all encodings - supported by the underlying JVM; previous versions handled only - UTF-8, UTF_16, ASCII, and ISO-8859-1.)</li> - -</ol> - -<p>As you can see from this list, Ælfred is designed for production -use, but neither validation nor perfect conformance was a requirement. -Good validating parsers exist, including one in this package, -and you should use them as appropriate. (See conformance reviews -available at <a href="http://www.xml.com/">http://www.xml.com</a>) -</p> - -<p> One of the main goals of Ælfred2 was to significantly improve -conformance, while not significantly affecting the other goals stated above. -Since the only use of this parser is with SAX, some classes could be -removed, and so the overall size of Ælfred was actually reduced. -Subsequent performance work produced a notable speedup (over twenty -percent on larger files). That is, the tradeoffs between speed, size, and -conformance were re-targeted towards conformance and support of newer APIs -(SAX2), with a a positive performance impact. </p> - -<p> The role anticipated for this version of Ælfred is as a -lightweight Free Software SAX parser that can be used in essentially every -Java program where the handful of conformance violations (noted below) -are acceptable. -That certainly includes applets, and -nowadays one must also mention embedded systems as being even more -size-critical. -At this writing, all parsers that are more conformant are -significantly larger, even when counting the optional -validation support in this version of Ælfred. </p> - - -<h3><a name="name">About the Name <em>Ælfred</em></a></h3> - -<p>Ælfred the Great (AElfred in ASCII) was King of Wessex, and -some say of King of England, at the time of his death in 899 AD. -Ælfred introduced a wide-spread literacy program in the hope that -his people would learn to read English, at least, if Latin was too -difficult for them. This Ælfred hopes to bring another sort of -literacy to Java, using XML, at least, if full SGML is too difficult.</p> - -<p>The initial Æ ligature ("AE)" is also a reminder that XML is -not limited to ASCII.</p> - - -<h3><a name="encodings">Character Encodings</a></h3> - -<p> The Ælfred parser currently builds in support for a handful -of input encodings. Of course these include UTF-8 and UTF-16, which -all XML parsers are required to support:</p> <ul> - - <li> UTF-8 ... the standard eight bit encoding, used unless - you provide an encoding declaration or a MIME charset tag.</li> - - <li> US-ASCII ... an extremely common seven bit encoding, - which happens to be a subset of UTF-8 and ISO-8859-1 as well - as many other encodings. XHTML web pages using US-ASCII - (without an encoding declaration) are probably more - widely interoperable than those in any other encoding. </li> - - <li> ISO-8859-1 ... includes accented characters used in - much of western Europe (but excluding the Euro currency - symbol).</li> - - <li> UTF-16 ... with several variants, this encodes each - sixteen bit Unicode character in sixteen bits of output. - Variants include UTF-16BE (big endian, no byte order mark), - UTF-16LE (little endian, no byte order mark), and - ISO-10646-UCS-2 (an older and less used encoding, using a - version of Unicode without surrogate pairs). This is - essentially the native encoding used by Java. </li> - - <li> ISO-10646-UCS-4 ... a seldom-used four byte encoding, - also known as UTF-32BE. Four byte order variants are supported, - including one known as UTF-32LE. Some operating systems - standardized on UCS-4 despite its significant size penalty, - in anticipation that Unicode (even with surrogate pairs) - would eventually become limiting. UCS-4 permits encoding - of non-Unicode characters, which Java can't represent (and - XML doesn't allow). - </li> - - </ul> - -<p> If you use any encoding other than UTF-8 or UTF-16 you should -make sure to label your data appropriately: </p> - -<blockquote> -<?xml version="1.0" encoding="<b>ISO-8859-15</b>"?> -</blockquote> - -<p> Encodings accessed through <code>java.io.InputStreamReader</code> -are now fully supported for both external labels (such as MIME types) -and internal types (as shown above). -There is one limitation in the support for internal labels: -the encodings must be derived from the US-ASCII encoding, -the EBCDIC family of encodings is not recognized. -Note that Java defines its -own encoding names, which don't always correspond to the standard -Internet encoding names defined by the IETF/IANA, and that Java -may even <em>require</em> use of nonstandard encoding names. -Please report -such problems; some of them can be worked around in this parser, -and many can be worked around by using external labels. -</p> - -<p>Note that if you are using the Euro symbol with an fixed length -eight bit encoding, you should probably be using the encoding label -<em>iso-8859-15</em> or, with a Microsoft OS, <em>cp-1252</em>. -Of course, UTF-8 and UTF-16 handle the Euro symbol directly. -</p> - - -<h3><a name="violations">Known Conformance Violations</a></h3> - -<p>Known conformance issues should be of negligible importance for -most applications, and include: </p><ul> - - <li> Rather than following the voluminous "Appendix B" rules about - what characters may appear in names (and name tokens), the Unicode - rules embedded in <em>java.lang.Character</em> are used. - This means mostly that some names are inappropriately accepted, - though a few are inappropriately rejected. (It's much simpler - to avoid that much special case code. Recent OASIS/NIST test - cases may have these rules be realistically testable.) </li> - - <li> Text containing "]]>" is not rejected unless it fully resides - in an internal buffer ... which is, thankfully, the typical case. This - text is illegal, but sometimes appears in illegal attempts to - nest CDATA sections. (Not catching that boundary condition - substantially simplifies parsing text.) </li> - - <li> Surrogate characters that aren't correctly paired are ignored - rather than rejected, unless they were encoded using UTF-8. (This - simplifies parsing text.) Unicode 3.1 assigned the first characters - to those character codes, in early 2001, so few documents (or tools) - use such characters in any case. </li> - - <li> Declarations following references to an undefined parameter - entity reference are not ignored. (Not maintaining and using state - about this validity error simplifies declaration handling; few - XML parsers address this constraint in any case.) </li> - - <li> Well formedness constraints for general entity references - are not enforced. (The code to handle the "content" production - is merged with the element parsing code, making it hard to reuse - for this additional situation.) </li> - -</ul> - -<p> When tested against the July 12, 1999 version of the OASIS -XML Conformance test suite, an earlier version passed 1057 of 1067 tests. -That contrasts with the original version, which passed 867. The -current parser is top-ranked in terms of conformance, as is its -validating sibling (which has some additional conformance violations -imposed on it by SAX2 API deficiencies as well as some of the more -curious SGML layering artifacts found in the XML specification). </p> - -<p> The XML 1.0 specification itself was not without problems, -and after some delays the W3C has come out with a revised -"second edition" specification. While that doesn't resolve all -the problems identified the XML specification, many of the most -egregious problems have been resolved. (You still need to drink -magic Kool-Aid before some DTD-related issues make sense.) -To the extent possible, this parser conforms to that second -edition specification, and does well against corrected versions -of the OASIS/NIST XML conformance test cases. See <a href= -"http://xmlconf.sourceforge.net">http://xmlconf.sourceforge.net</a> -for more information about SAX2/XML conformance testing. </p> - - -<h3><a name="copyright">Copyright and distribution terms</a></h3> - -<p> -The software in this package is distributed under the GNU General Public -License (with a special exception described below). -</p> - -<p> -A copy of GNU General Public License (GPL) is included in this distribution, -in the file COPYING. If you do not have the source code, it is available at: - - <a href="http://www.gnu.org/software/classpath/">http://www.gnu.org/software/classpath/</a> -</p> - -<pre> - Linking this library statically or dynamically with other modules is - making a combined work based on this library. Thus, the terms and - conditions of the GNU General Public License cover the whole - combination. - - As a special exception, the copyright holders of this library give you - permission to link this library with independent modules to produce an - executable, regardless of the license terms of these independent - modules, and to copy and distribute the resulting executable under - terms of your choice, provided that you also meet, for each linked - independent module, the terms and conditions of the license of that - module. An independent module is a module which is not derived from - or based on this library. If you modify this library, you may extend - this exception to your version of the library, but you are not - obligated to do so. If you do not wish to do so, delete this - exception statement from your version. - - Parts derived from code which carried the following notice: - - Copyright (c) 1997, 1998 by Microstar Software Ltd. - - AElfred is free for both commercial and non-commercial use and - redistribution, provided that Microstar's copyright and disclaimer are - retained intact. You are free to modify AElfred for your own use and - to redistribute AElfred with your modifications, provided that the - modifications are clearly documented. - - This program is distributed in the hope that it will be useful, but - WITHOUT ANY WARRANTY; without even the implied warranty of - merchantability or fitness for a particular purpose. Please use it AT - YOUR OWN RISK. -</pre> - -<p> Some of this documentation was modified from the original -Ælfred README.txt file. All of it has been updated. </p> - -</p> - - -<h2><a name="changes">Changes Since the last Microstar Release</a></h2> - -<p> As noted above, Microstar has not updated this parser since -the summer of 1998, when it released version 1.2a on its web site. -This release is intended to benefit the developer community by -refocusing the API on SAX2, and improving conformance to the extent -that most developers should not need to use another XML parser. </p> - -<p> The code has been cleaned up (referring to the XML 1.0 spec in -all the production numbers in -comments, rather than some preliminary draft, for one example) and -has been sped up a bit as well. -JAXP support has been added, although developers are still -strongly encouraged to use the SAX2 APIs directly. </p> - - -<h3><a name="sax2">SAX2 Support</a></h3> - -<p> The original version of Ælfred did not support the -SAX2 APIs. </p> - -<p> This version supports the SAX2 APIs, exposing the standard -boolean feature descriptors. It supports the "DeclHandler" property -to provide access to all DTD declarations not already exposed -through the SAX1 API. The "LexicalHandler" property is supported, -exposing entity boundaries (including the unnamed external subset) and -things like comments and CDATA boundaries. SAX1 compatibility is -currently provided.</p> - - -<h3><a name="validation">Validation</a></h3> - -<p> In the 'pipeline' package in this same software distribution is an -<a href="../pipeline/ValidationConsumer.html">XML Validation component</a> -using any full SAX2 event stream (including all document type declarations) -to validate. There is now a <a href="XmlReader.html">XmlReader</a> class -which combines that class and this enhanced Ælfred parser, creating -an optionally validating SAX2 parser. </p> - -<p> As noted in the documentation for that validating component, certain -validity constraints can't reliably be tested by a layered validator. -These include all constraints relying on -layering violations (exposing XML at the level of tokens or below, -required since XML isn't a context-free grammar), some that -SAX2 doesn't support, and a few others. The resulting validating -parser is conformant enough for most applications that aren't doing -strange SGML tricks with DTDs. -Moreover, that validating filter can be used without -a parser ... any application component that emits SAX event streams -can DTD-validate its output on demand. </p> - -<h3><a name="smaller">You want Smaller?</a></h3> - -<p> You'll have noticed that the original version of Ælfred -had small size as a top goal. Ælfred2 normally includes a -DTD validation layer, but you can package without that. -Similarly, JAXP factory support is available but optional. -Then the main added cost due to this revision are for -supporting the SAX2 API itself; DTD validation is as -cleanly layered as allowed by SAX2.</p> - -<h3><a name="bugfixes">Bugs Fixed</a></h3> - -<p> Bugs fixed in Ælfred2 include: </p> - -<ol> - <li> Originally Ælfred didn't close file descriptors, which - led to file descriptor leakage on programs which ran for any - length of time. </li> - - <li> NOTATION declarations without system identifiers are - now handled correctly. </li> - - <li> DTD events are now reported for all invocations of a - given parser, not just the first one. </li> - - <li> More correct character handling: <ul> - - <li> Rejects out-of-range characters, both in text and in - character references. </li> - - <li> Correctly handles character references that expand to - surrogate pairs. </li> - - <li> Correctly handles UTF-8 encodings of surrogate pairs. </li> - - <li> Correctly handles Unicode 3.1 rules about illegal UTF-8 - encodings: there is only one legal encoding per character. </li> - - <li> PUBLIC identifiers are now rejected if they have illegal - characters. </li> - - <li> The parser is more correct about what characters are allowed - in names and name tokens. Uses Unicode rules (built in to Java) - rather than the voluminous XML rules, although some extensions - have been made to match XML rules more closely.</li> - - <li> Line ends are now normalized to newlines in all known - cases. </li> - - </ul></li> - - <li> Certain validity errors were previously treated as well - formedness violations. <ul> - - <li> Repeated declarations of an element type are no - longer fatal errors. </li> - - <li> Undeclared parameter entity references are no longer - fatal errors. </li> - - </ul></li> - - <li> Attribute handling is improved: <ul> - - <li> Whitespace must exist between attributes. </li> - - <li> Only one value for a given attribute is permitted. </li> - - <li> ATTLIST declarations don't need to declare attributes. </li> - - <li> Attribute values are normalized when required. </li> - - <li> Tabs in attribute values are normalized to spaces. </li> - - <li> Attribute values containing a literal "<" are rejected. </li> - - </ul></li> - - <li> More correct entity handling: <ul> - - <li> Whitespace must precede NDATA when declaring unparsed - entities.</li> - - <li> Parameter entity declarations may not have NDATA annotations. </li> - - <li> The XML specification has a bug in that it doesn't specify - that certain contexts exist within which parameter entity - expansion must not be performed. Lacking an offical erratum, - this parser now disables such expansion inside comments, - processing instructions, ignored sections, public identifiers, - and parts of entity declarations. </li> - - <li> Entity expansions that include quote characters no longer - confuse parsing of strings using such expansions. </li> - - <li> Whitespace in the values of internal entities is not mapped - to space characters. </li> - - <li> General Entity references in attribute defaults within the - DTD now cause fatal errors when the entity is not defined at the - time it is referenced. </li> - - <li> Malformed general entity references in entity declarations are - now detected. </li> - - </ul></li> - - <li> Neither conditional sections - nor parameter entity references within markup declarations - are permitted in the internal subset. </li> - - <li> Processing instructions whose target names are "XML" - (ignoring case) are now rejected. </li> - - <li> Comments may not include "--".</li> - - <li> Most "]]>" sequences in text are rejected. </li> - - <li> Correct syntax for standalone declarations is enforced. </li> - - <li> Setting a locale for diagnostics only produces an exception - if the language of that locale isn't English. </li> - - <li> Some more encoding names are recognized. These include the - Unicode 3.0 variants of UTF-16 (UTF-16BE, UTF-16LE) as well as - US-ASCII and a few commonly seen synonyms. </li> - - <li> Text (from character content, PIs, or comments) large enough - not to fit into internal buffers is now handled correctly even in - some cases which were originally handled incorrectly.</li> - - <li> Content is now reported for element types for which attributes - have been declared, but no content model is known. (Such documents - are invalid, but may still be well formed.) </li> - -</ol> - -<p> Other bugs may also have been fixed. </p> - -<p> For better overall validation support, some of the validity -constraints that can't be verified using the SAX2 event stream -are now reported directly by Ælfred2. </p> - -</body></html> - |