5 XML library is used by several field 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 named Mono.Xml.MiniParser.
12 Basically System.XML.dll feature has finished, or almost finished, so
13 I write this page mainly for bugs and improvement hints.
16 ** System.Xml namespace
19 *** Document Object Model (Core)
21 DOM feature has already implemented. There is still missing feature.
24 * ID constraint support is problematic because W3C DOM does not
25 specify handling of ID attributes into non-adapted element.
26 (MS.NET also looks incomplete in this area).
27 * I think, event feature is not fully tested. There are no
28 concrete desctiption on which events are risen, so we have to
29 do some experiment on MS.NET.
34 Here XmlWriter almost equals to XmlTextWriter. If you want to see
35 another implementation, check XmlNodeWriter.cs used in monodoc.
37 XmlTextWriter is completed. However, it looks slower than MS.NET (I
38 tried 1.1). After some optimization, it became better, but maybe it can be
43 Currently XmlTextReader uses specified XmlResolver. If nothing was supplied,
44 then it uses XmlUrlResolver. XmlResolver is used to parse external DTD,
45 importing XSL stylesheets and schemas etc.
47 However, XmlUrlResolver is still buggy (mainly because System.Uri is also
48 incomplete yet) and this results in several loading error.
50 XmlSecureResolver, which is introduced in MS .NET Framework 1.1 is basically
51 implemented, but it requires CAS (code access security) feature. We need to
52 fixup this class after ongoing CAS effort works.
54 You might also be interested in an improved <a href="http://codeblogs.ximian.com/blogs/benm/archives/000039.html">XmlCachingResolver</a> by Ben Maurer.
58 XmlNameTable itself is implemented. However, it should be actually used in
59 several classes. Currently it makes sense if compared names are both in
60 the table, they should be simply compared using ReferenceEquals(). We
61 have partially done in XmlNamespaceManager (in .NET 1.2 methods; if the
62 build is not NET_1_2 then it is internal use only).
66 When we are using ASCII document, we don't care which encoding we are using.
67 However, XmlTextReader must be aware of the specified encoding in XML
68 declaration. So we have internal XmlStreamReader class (and currently
69 XmlInputStream class. This may disappear since XmlStreamReader is enough to
72 However, there seems some problems in these classes on reading network
73 stream (especially on Linux). This should be fixed soon, if we found the
78 XmlTextReader, XmlNodeReader and XmlValidatingReader are almost finished.
81 * All OASIS conformance test passes as Microsoft does. Some
82 W3C tests fail, but it looks better.
83 * Entity expansion and its well-formedness check is incomplete.
84 It incorrectly allows divided content models. It incorrectly
85 treats its Base URI, so some dtd fails.
86 * Unicode surrogate pair character is not supported yet.
87 * I won't add any XDR support on XmlValidatingReader. (I haven't
88 ever seen XDR used other than Microsoft's BizTalk Server 2000,
89 and Now they have 2002 with XML Schema support)
92 XmlTextReader and XmlValidatingReader should be faster than now. Currently
93 XmlTextReader looks nearly twice as slow as MS.NET, and XmlValidatingReader
94 (which uses this slow XmlTextReader) looks nearly three times slower. (Note
95 that XmlValidatingReader won't be slow as itself. It uses schema validating
96 reader and dtd validating reader.)
101 The design of Mono's XmlValidatingReader is radically different from
102 that of Microsoft's implementation. Under MS.NET, DTD content validation
103 engine is in fact simple replacement of XML Schema validation engine.
104 Mono's DTD validation is designed fully separate and does validation
105 as normal XML parser does. For example, Mono allows non-deterministic DTD.
107 Another advantage of this XmlValidatingReader is support for *any* XmlReader.
108 Microsoft supports only XmlTextReader.
110 I added extra support interface named "IHasXmlParserContext", which is
111 considered in XmlValidatingReader.ResolveEntity(). Microsoft failed to
112 design XmlReader to support pluggable use of XmlReader (i.e. wrapping use
113 of other XmlReader) since XmlParserContext is required to support both
114 entity resolution and namespace manager. (In .NET 1.2, Microsoft also
115 supported similar to IHasXmlParserContext, named IXmlNamespaceResolver,
116 but it still does not provide any DTD information.)
118 We also have RELAX NG validating reader. See mcs/class/Commons.Xml.Relaxng.
125 Basically it is completed. We can compile complex and simple types, refer to
126 external schemas, extend or restrict other types, or use substitution groups.
127 You can test how current schema validation engine is (in)complete by using
128 standalone test module
129 (see mcs/class/System.XML/Test/System.Xml.Schema/standalone_tests).
130 At least in my box, msxsdtest fails only 30 cases with bugfixed catalog.
132 *** Schema Object Model
134 Completed, except for some things to be fixed:
137 * Complete facet support. Currently some of them is missing.
138 Recently David Sheldon is doing several fixes on them.
139 * ContentTypeParticle for pointless xs:choice is incomplete
140 (It is because fixing this arose another bugs in
141 compilation. Interestingly, MS.NET also fails around here,
142 so it might be nature of ContentTypeParticle design)
143 * Some derivation by restriction (DBR) handling is incorrect.
144 * Some simple type restriction handling is still incorrect.
147 *** Validating Reader
149 XML Schema validation feature is (currently) implemented on
150 Mono.Xml.Schema.XsdValidatingReader, which is internally used in
153 Basically this is implemented and actually its feature is almost complete,
154 but I have only did validation feature testing. So we have to write more
155 tests on properties, methods, and events (validation errors).
158 ** System.Xml.Serialization
162 Well, in fact XmlSerializer is almost finished and is on bugfix phase.
164 However, we appliciate more tests. Please try
167 * System.Web.Services to invoke SOAP services.
168 * xsd.exe and wsdl.exe to create classes.
171 And if any problems were found, please file it to bugzilla.
173 Lluis also built interesting standalone test system placed under
174 mcs/class/System.Web.Services/Test/standalone.
176 You might also interested in genxs, which enables you to create custom
177 XML serializer. This is not included in Microsoft.NET.
178 See mcs/tools/genxs for the details.
181 ** System.Xml.XPath and System.Xml.Xsl
183 There are two implementations for XSLT. One (and historical) implementation
184 is based on libxslt (aka Unmanaged XSLT). Now we uses fully implemented
185 managed XSLT. To use Unmanaged XSLT, set MONO_UNMANAGED_XSLT environment
186 value (any value is acceptable).
188 As for Managed XSLT, we support msxsl:script.
190 It would be nice if we can support <a href="http://www.exslt.org/">EXSLT</a>.
191 <a href="http://msdn.microsoft.com/WebServices/default.aspx?pull=/library/en-us/dnexxml/html/xml05192003.asp">Microsoft has already done it</a>, but it
192 is not good code since it depends on internal concrete derivatives of
193 XPathNodeIterator classes. In general, .NET's "extension objects" is not
194 usable to return node-sets, so if we support EXSLT, it has to be done
195 internally inside our System.XML.dll. Volunteers are welcome.
197 Our managed XSLT implementation is still inefficient. XslTransform.Load()
198 and .Transform() looks three times slower (However it depends on
199 XmlTextReader which is also slow, so we are starting optimization from
200 that class, not XSLT itself). These number are only for specific cases,
201 and there might be more critical point on XSLT engine (mainly
205 ** System.Xml and ADO.NET v2.0
207 Microsoft introduced the first beta version of .NET Framework 1.2 runtime
208 and sdk (and Visual Studio Whidbey). They are now available on MSDN
209 _subscriber_ download (i.e. it is not publicly downloadable yet). It
210 contains several new classes.
212 There are two assemblies related to System.Xml v2.0; System.Xml.dll and
213 System.Data.SqlXml.dll (here I treat sqlxml.dll as part of System.Xml v2.0,
214 but note that it is also one of the ADO.NET 2.0 feature). There are several
215 namespaces such as MS.Internal.Xml and System.Xml. Note that .NET Framework
216 is pre-release version and MS.Internal.Xml namespace apparently shows that
217 it is not in stable status as yet.
219 System.Xml 2.0 contains several features such as:
222 * XPathNavigator2 and XPathDocument2
225 * XSLT IL generator (similar to Apache XSLTC) - it is
229 Tim Coleman started ADO.NET 2.0 related works. Currently I have no plan to
230 implement System.Xml v2.0 classes and won't touch with them immediately,
231 but will start in next some months. If any of you wants to try this
232 frontier, we welcome your effort.
236 System.Xml v2.0 implementation will be started from XPathDocument2 and
237 XPathNavigator2 implementations. Firstly, its document structure and
238 basic navigation feature will be implemented. And next, XPath2 engine
239 should be implemented (XPathNavigator2 looks very different from
240 XPathNavigator). Another requirement is schema based validation feature.
241 It needs some schema improvements, such like IXmlInfosetReader support.
242 (IXmlInfosetReader is in MS.Internal.Xml.)
246 XML Query is a new face XML data manipulation language (well, at least new
247 to .NET world). It is similar to SQL, but intended to manipulate and to
248 support XML. It is similar to XSLT, but extended to support new features
249 such as XML Schema based datatypes.
251 XML Query implementation can be found mainly in System.Xml.Query and
252 MS.Internal.Xml.Query namespaces. Note that they are in
253 System.Data.SqlXml.dll.
255 MSDN documentation says that there are two kind of API for XML Query: High
256 Level API and Low Level API. At the time of this beta version, the Low Level
257 API is described not released yet (though it may be MS.Internal.Xml.*
258 classes). However, to implement the High Level API, the Low Level API will
259 be used. They looks to have interesting class structures in MS.Internal.Xml
260 related stuff, so it would be nice (and I will) start to learn about them.
262 They looks to have IL generator classes, but it would be difficult to
265 *** System.Data.Mapping
267 System.Data.Mapping and System.Data.Mapping.RelationalSchema are the
268 namespaces for mapping support between database and xml. This is at
269 stubbing phase (incomplete as yet).
273 XmlAdapter is used to support XML based query and update using
274 XPathDocument2 and XPathNavigator2. This class is designed to synthesize
275 ADO.NET and System.Xml. It connects to databases, and querys data however
276 in XML shape into XPathDocument2, using Mapping schema above. This must be
277 done after several classes such as XPathDocument2 and MappingSchema.
280 ** Miscellaneous Class Libraries
284 I implemented an experimental RelaxngValidatingReader. It is far from
285 complete, especially simplification stuff (see RELAX NG spec chapter 4),
286 some constraints (in chapter 7), and datatype handling.
288 I am planning improvements (starts with renaming classes, giving more
289 kind error messages, supporting compact syntax and even object mapping),
290 but it is still my wishlist.
297 See <a href="ado-net.html">ADO.NET page</a>.
299 Microsoft has another inference class from XmlReader to XmlSchemaCollection
300 (Microsoft.XsdInference). It may be useful, but it won't be so easy.
305 Sometimes I hear complain about System.dll and System.Xml.dll mutual
306 dependency: System.dll references to System.Xml.dll (e.g.
307 System.Configuration.ConfigXmlDocument extended from XmlDocument), while
308 System.Xml.dll vice versa (e.g. XmlUrlResolver.ResolveUri takes System.Uri).
309 Since they are in public method signatures, so at least we cannot get rid
310 of these mutual references.
312 However, for those who really want to build System.Xml.dll without System.dll,
313 I created <a href="http://primates.ximian.com/~atsushi/System_DummyClasses.cs">dummy classes in System.dll</a>. To build System.Xml.dll in such way, remove
314 <code>/r:System.dll</code> from Makefile, and add this source to
315 System.Xml.dll.sources. Note that this is at the point of Mono 0.30 release.
317 Also note that you still need System.dll to run mcs.