1 * XML Classes Status and Tasks
5 XML library is used by several areas of Mono such as ADO.NET and XML
6 Digital Signature (xmldsig). Here I write about System.Xml.dll and
7 related tools. This page won't include any classes which are in other
8 assemblies such as XmlDataDocument.
10 Note that current corlib has its own XML parser class (Mono.Xml.MiniParser).
12 Basically System.XML.dll feature is almost finished, so I write this
13 document mainly for bugs and improvement hints.
17 *** System.Xml namespace
20 **** Document Object Model (Core)
22 DOM implementation has finished and our DOM implementation scores better
23 than MS.NET as to the NIST DOM test results (it is ported by Mainsoft
24 hackers and in our unit tests).
28 Here XmlWriter almost equals to XmlTextWriter. If you want to see
29 another implementation, check XmlNodeWriter.cs and DTMXPathDocumentWriter.cs
30 in System.XML sources.
32 XmlTextWriter is completed, though it looks a bit slower than MS.NET (I
37 XmlUrlResolver is implemented.
39 XmlSecureResolver, which is introduced in MS .NET Framework 1.1 is basically
40 implemented, but it requires CAS (code access security) feature. We need to
41 fixup this class after ongoing CAS effort works.
43 You might also be interested in an improved <a href="http://codeblogs.ximian.com/blogs/benm/archives/000039.html">XmlCachingResolver</a> by Ben Maurer.
44 If even one time download is not acceptable, you can use <a href="http://primates.ximian.com/~atsushi/XmlStoredResolver.cs">this one</a>.
46 [2.0] XmlDataSourceResolver is not implemented as yet.
50 NameTable is implemented, but also needs performance improvement.
51 It affects on the whole XML processing performance so much.
52 Optimization hackings are welcome. There is also a <a
53 href="http://bugzilla.ximian.com/show_bug.cgi?id=59537">bugzilla entry</a>
58 XmlTextReader, XmlNodeReader and XmlValidatingReader are almost finished.
61 * All OASIS conformance test passes as Microsoft does. Some
62 W3C tests fail, but it looks better.
63 * Entity expansion and its well-formedness check is incomplete.
64 It incorrectly allows divided content models. It incorrectly
65 treats its Base URI, so some dtd parse fails.
66 * I won't add any XDR support on XmlValidatingReader. (I haven't
67 ever seen XDR used other than Microsoft's BizTalk Server 2000,
68 and Now they have 2002 with XML Schema support). If anyone
69 contributes an implementation, it would be still nice.
72 XmlTextReader and XmlValidatingReader should be faster than now. Currently
73 XmlTextReader looks nearly twice as slow as MS.NET, and XmlValidatingReader
74 (which uses this slow XmlTextReader) looks nearly three times slower. (Note
75 that XmlValidatingReader wouldn't be so slow as itself. It uses schema
76 validating reader and dtd validating reader.)
81 The design of Mono's XmlValidatingReader is radically different from
82 that of Microsoft's implementation. Under MS.NET, DTD content validation
83 engine is in fact simple replacement of XML Schema validation engine.
84 Mono's DTD validation is designed fully separate and does validation
85 as normal XML parser does. For example, Mono allows non-deterministic DTD.
87 Another advantage of this XmlValidatingReader is support for *any* XmlReader.
88 Microsoft supports only XmlTextReader (this bug is fixed in .NET 2.0 beta,
89 taking shape of XmlReader.Create()).
91 <del>I added extra support interface named "IHasXmlParserContext", which is
92 considered in XmlValidatingReader.ResolveEntity(). </del><ins>This is now
93 made as internal interface.</ins> Microsoft failed to design XmlReader
94 so that XmlReader cannot be subtree-pluggable (i.e. wrapping use of other
95 XmlReader) since XmlParserContext shoud be supplied for DTD information
96 support (e.g. entity references cannot be expanded) and namespace manager.
97 (In .NET 2.0, Microsoft also supported similar to IHasXmlParserContext,
98 named IXmlNamespaceResolver, but it still does not provide DTD information.)
100 We also have RELAX NG validating reader (described later).
103 *** System.Xml.Schema
107 Basically it is completed. You can test how current schema validation engine
108 is complete (incomplete) by using standalone test module (see
109 mcs/class/System.XML/Test/System.Xml.Schema/standalone_tests).
110 At least in my box, msxsdtest fails only 30 cases with bugfixed catalog -
111 this score is better than that of Microsoft implementation. But instead,
112 we need performance boost. There should be many points to improve
113 schema compilation and validation.
115 **** Schema Object Model
117 Completed, except for some things to be fixed:
120 * Complete facet support. Currently some of them is missing.
121 Recently David Sheldon is doing several fixes on them.
122 * ContentTypeParticle for pointless xs:choice is incomplete
123 (fixing this arose another bugs in compilation.
124 Interestingly, MS.NET also fails around here, so it might
125 be nature of ContentTypeParticle design)
126 * Some derivation by restriction (DBR) handling is incorrect.
129 **** Validating Reader
131 Basically this is implemented and actually its feature is complete,
132 but I have only did validation feature testing. So we have to write more
133 tests on properties, methods, and events (validation errors).
136 *** System.Xml.Serialization
140 Well, in fact XmlSerializer is almost finished and is on bugfix phase.
142 However, we appliciate more tests. Please try
145 * System.Web.Services to invoke SOAP services.
146 * xsd.exe and wsdl.exe to create classes.
149 And if any problems were found, please file it to bugzilla.
151 Lluis also built interesting standalone test system placed under
152 mcs/class/System.Web.Services/Test/standalone.
154 You might also interested in "genxs", which enables you to create custom
155 XML serializer. This is not included in Microsoft.NET.
157 href="http://primates.ximian.com/~lluis/blog/archives/000120.html">here</a>
158 and manpages for details. Code files are in mcs/tools/genxs.
160 Lluis also created "sgen", that based on XmlSerializer.GenerateSerializer().
161 Code files are in mcs/tools/sgen.
163 *** System.Xml.XPath and System.Xml.Xsl
165 There are two XSLT implementations. One and historical implementation is
166 based on libxslt (aka Unmanaged XSLT). Now we uses fully implemented and
167 managed XSLT by default. To use Unmanaged XSLT, set MONO_UNMANAGED_XSLT
168 environment value (any value is acceptable).
170 As for Managed XSLT, we support msxsl:script.
172 It would be nice if we can support <a href="http://www.exslt.org/">EXSLT</a>.
173 <a href="http://msdn.microsoft.com/WebServices/default.aspx?pull=/library/en-us/dnexxml/html/xml05192003.asp">Microsoft has tried to do some of them</a>,
174 but it is not successful because of System.Xml.Xsl design problem:
177 * In general, .NET's "extension objects" (including
178 msxsl:script) is not useful to return node-sets (MS XSLT
179 implementation rejects just overriden XPathNodeIterator,
180 but accepts only their hidden classes. And are the same
181 in Mono though classes are different)
183 * In .NET's extension object design, extension function name
184 is a valid method name that cannot contain some characters
185 such as '-'. That is, implementing EXSLT in C# is impossible.
188 So if we support EXSLT, it has to be done inside our System.XML.dll.
189 Microsoft developers are also aware of this problem and some of them wish
190 to have EXSLT support in WinFX (not whidbey). If anyone is interested
191 in it, it would be nice.
193 Our managed XSLT implementation is slower than MS XSLT for some kind of
194 stylesheets, and faster for some.
199 I implemented an experimental RelaxngValidatingReader. It is still not
200 complete, for example some simplification stuff (see RELAX NG spec
201 chapter 4; especially 4.17-19) and some constraints (especially 7.3).
202 See mcs/class/Commons.Xml.Relaxng/README for details.
207 * Custom datatype support. Right now, you can use XML schema
208 datatypes ( http://www.w3.org/2001/XMLSchema-datatypes )
209 as well as RELAX NG default datatypes (as used in relaxng.rng).
211 * RELAX NG Compact Syntax support, though not yet stable.
212 See Commons.Xml.Relaxng.Rnc.RncParser class.
220 Microsoft released the first public beta version of .NET Framework 2.0,
221 available from <a href="http://www.microsoft.com/downloads/details.aspx?familyid=916EC067-8BDC-4737-9430-6CEC9667655C&displaylang=en">MSDN</a>.
222 It contains several new classes.
224 There are two assemblies related to System.Xml v2.0; System.Xml.dll and
225 System.Data.SqlXml.dll. Most of the important part are in System.Xml.dll
226 (you will find that the core part of XQuery is in System.Xml.dll; see some
227 classes in MS.Internal.Xml namespace), so I'll still spot only on
230 Note that .NET Framework is pre-release version so that they are subject
233 System.Xml 2.0 contains several features such as:
236 * new XPathNavigator and XPathDocument
237 * Factory method based and strongly-typed XmlReader
238 * XML Schema design changes
240 * XQuery implementation
241 * Well-documented and improved XmlSerializer.
242 * XSLT IL generator (similar to Apache XSLTC) - it is
246 **** XmlReader.Create() and ReadValueAsXxx()
248 In .NET 2.0, XmlTextReader, XmlNodeReader, XmlValidatingReader are
249 obsolete and XmlReader.Create() is recommended (there is however no
250 alternative way to create XmlNodeReader).
252 As for typed XmlReader support, we need something like XQueryConvert that
253 is like XmlConvert but based on XQuery 1.0 and XPath 2.0 data model.
255 **** XML Schema design changes
257 Since .NET 1.x is not so compliant with W3C XML Schema specification,
258 Microsoft had to redesign System.Xml.Schema classes. We also have to
263 In .NET 2.0, there is an XML Schema inference implementation. Once
264 XmlSchemaSet is implemented, it can be separately done by anyone.
265 Volunteer efforts are welcome here.
267 **** New XPathNavigator
269 System.Xml v2.0 implementation will be started from new XPathNavigator
270 implementation. First, its document structure and basic navigation feature
271 will be implemented. And next, XPath2 engine should be implemented
272 (XPathNavigator2 looks very different from XPathNavigator).
274 My current plan is to implement editable interface for XmlDocumentNavigator
275 (XPathNavigator from XmlDocument). Our XPathDocument is index-based
276 implementation, and thus it cannot be modified to be editable as it is.
278 There are some trivial tasks such as schema validation (we have
279 <a href="http://www24.brinkster.com/ginga/XPathDocumentReader.cs.txt">
280 XPathDocumentReader</a> that just wraps XPathNavigator, and our
281 XmlValidatingReader can accept any XmlReader).
285 XQuery is a new face XML data manipulation language (well, at least new
286 face in .NET world). It is similar to SQL, but intended to manipulate and to
287 support XML. It is similar to XPath, but extended to support new features
288 such as XML Schema based datatypes.
290 XQuery implementation can be found mainly in System.Xml.Query and
291 MS.Internal.Xml.Query namespaces. <del>Note that they are in
292 System.Data.SqlXml.dll</del><ins> The implementation is mostly
293 in System.Xml.dll</ins>.
295 XQuery implementation will be done in these steps:
298 * XQuery syntax parser that parses xquery string to AST
299 (abstract syntax tree).
301 * XQuery AST compiler into runnable query command (not done yet)
303 * XQuery (dynamic context) runtime = XQuery expression evaluator
306 * Applied expression classes for XQuery/XPath 2.0 functions and
309 * XQuery data model and (mainly) conversion support.
312 **** Relax NG and DSDL in Mono 1.2
314 Currently we support only RELAX NG as one part of ISO DSDL effort. There
315 is existing Schematron implementation (NMatrix Project: <a
316 href="http://sourceforge.net/projects/dotnetopensrc/">
317 http://sourceforge.net/projects/dotnetopensrc/</a>). With a few changes,
318 it can be used with mono.
320 We also don't have multi-language based validation, namely Namespace-based
321 Validation Dispatch Language (NVDL). To support unwrapping, one special
322 XmlReader implementation is required. Note that we had seen RELAX Namespace,
323 Modular Namespace (MNS) and Namespace Routing Language (NRL) - that is,
324 standardization effort is still ongoing (though NVDL looks mostly the same
327 In Mono 1.2, there might be improvements on Commons.Xml.Relaxng.
330 * Currently RelaxngPattern.Compile() provides cheap compilation
331 error information. At least it can provide error location.
332 Also, the type of error should be kind of
333 RelaxngGrammarException.
335 * Right now there is no ambiguity detection implementation that
336 would be useful for RelaxngPattern based xml serialization (if
345 See <a href="ado-net.html">ADO.NET page</a>.
347 Microsoft has another inference class from XmlReader to XmlSchemaCollection
348 (Microsoft.XsdInference). It may be useful, but it won't be so easy.
353 *** Mutual assembly dependency
355 Sometimes I hear complain about System.dll and System.Xml.dll mutual
356 dependency: System.dll references to System.Xml.dll (e.g.
357 System.Configuration.ConfigXmlDocument extended from XmlDocument), while
358 System.Xml.dll vice versa (e.g. XmlUrlResolver.ResolveUri takes System.Uri).
359 Since they are in public method signatures, so at least we cannot get rid
360 of these mutual references.
362 Nowadays System.Xml.dll is built using incomplete System.dll (lacking
363 System.Xml dependent classes such as ConfigXmlDocument). Full System.dll
364 is built after System.Xml.dll is done.
366 Note that you still need System.dll to run mcs.
369 Atsushi Eno <asushi@ximian.com>
370 last updated 07/11/2004