https://github.com/cran/XML
Tip revision: 7c44787d022ce63fc21b058c61d11590cd125781 authored by Duncan Temple Lang on 03 May 2017, 09:28:58 UTC
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Tip revision: 7c44787
Todo-orig.html
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<title>Todo list for R-level XML Parser</title>
<link rel=stylesheet href="../../../Docs/OmegaTech.css" >
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<h1>Todo list for R-level XML Parser</h1>
<dl>
<dt>
<li> insert into a node at a particular position
<dd>
<dt>
<li> creation of internal entities, PIs, etc.
<dd> PIs done.
<dt>
<li> Connect the memory management with R's.
<dd>
<dt>
<li> Tidy up interface for add and remove nodes.
<dd>
<dl>
<dt>
<li> Add/append child to an XMLInternalNode
<dd> addChildren() - document.
<dt>
<li> Ability to remove a node from the children of a node.
<dd>
</dl>
<dt>
<li> Add support for the pull data source for xmlTreeParse and htmlTreeParse.
<dd> Not particularly important as efficiency shouldn't be that
important.
<dt>
<li> Switch to putting the namespace as the name of the element name
at the S level.
<dd>
<dt>
<li> Avoid the handler functions having names that could conflict
with tag names.
<dd> i.e. use .text, etc.
<dt>
<li> Fix the attributes in the event parsing.
<dd> They should have a method for xmlGetAttr.
There is a trailing "" element with no name.
And they have no class.
<dt>
<li> Strategies and actions
<dd> ???
<dt> "xmlValidNode" class
that "guarantees" children are valid XML nodes.
<dd> xmlTreeParse uses this if no handlers.
Otherwise, general non-validated XML node.
No constraint on children.
<dt>
<li> S-level Exceptions from XML.
<dd> Errors, warnings, etc. collected and available
after parsing for structured/programmatic access.
<dt>
<li> Add the base, etc. information to the Input buffer
when using a connection or function in the event parsing.
<dd>
<dt>
<li> Allow connections to be used when generating
an XML tree via libxml.
<dd> Works for SAX. Not likely to do it for DOM since
one can effectively read the entire document in
via a connection to a string and go from there.
It is not the same thing, but that's the way it is.
<dt>
<li> When parsing a DTD as raw text (i.e. not from a file),
getting warnings about subsets, etc.
<dd> lists
This happens in libxml 2 2.4.13, etc. but not 2.5.4
<dt>
<dd> Add DOCTYPE and DTD to <code>xmlTree()</code>
<dt>
<dt>
<li> Add handlers for different namespaces to <code>xmlTree()</code>
<dd>
A user can do this with an S-level handler
that maintains a list of lists of handler
functions grouped by namespace.
<dt>
<li> Finalizers for libxml nodes/docs.
<dd>
<li>
<pre>
dtdFile <- system.file("data/foo.dtd", pkg="XML")
> foo.dtd <- parseDTD(dtdFile)
> tmp <- dtdElement("variable", foo.dtd)
Error in dtd$elements[[name]] : object is not subsettable
> foo.dtd$elements
""ExternalDTD""
</pre>
<dd>
<dt>
<li> Appears to be an oddity on Solaris with the event driven
parsing.
<dd>
<pre>
source("dataFrameHandler.R")
z <- xmlEventParse("../DTDs/Examples/mtcars.xml", handler=handler())
</pre>
causes problems with an incorrect number of elements in the
third record. It reads the 22.8 as 2 and then 2.8
Removing some of the spaces before the 22.8 at the beginning of
the record makes this go away. Need to investigate further.
<br>
Looks like simply multiple text fragments being passed in separate calls.
<dt>
<li> Develop DTDs for basic types.
<dd>
<dt>
<li> Additional chapter/package to write XML
<dd> Handle standard types such as data frame, time series, factors,
graphics/plots, etc.
<p>
Can <code>cat()</code> output or <code>paste()</code>, but
can do more to ensure well-formed documents relative to a DTD.
Have a filter that knows what DTD, or collection of DTDs, to use
and how to ensure that individual calls do the correct thing in
the context. So basically keep a cursor.
<br>
Can read DTDs within this one. The filter can be built from this.
See <a href="WritingXML.html">Writing XML</a>.
<dt>
<li> Facility for dynamically modifying the user-level handler functions
for a parser from the body of one of these handlers.
<dd> For example, the document may contain its own functions for a
particular
language and we would see these in the preamble and switch to
using them.
<dt>
<li> Add facility for stopping the parsing mid-way through via a
call to stop() or whatever, but that doesn't cause an error.
<dd> Exceptions may work when Robert finishes these.
<dt>
<li> We can make this significantly more class-based,
i.e. object oriented.
<dd>
<dt>
<li> Process external entities.
<dd> These are not currently being seen by the event
mechanism. Probably a switch needs to be turned on.
<br>
Fixed now!
<br>
At present, internal references are substituted directly.
See test.xml in Docs directory.
<code>h <- .Call("R_XMLParse", "Docs/test.xml",xmlHandler(), F, F)</code>
<br>
See replaceEntities in <code>xmlTreeParse()</code>.
<dt>
<li> We could kill off the children element in a node
if there aren't any.
<dd>
<dt>
<li> <code>[</code> and <code>[<-</code> methods for the different types of nodes.
And also functions such as those in the w3c spec
for nodes, getElementsByTagName, etc.
<dd>
<dt>
<li> Also add the <code>[[</code> for accessing children, avoiding
the need for <code>$children[[]]</code>.
<dd> Done.
<dt>
<li> Could kill off the attributes and/or children for certain node types
such as comment, text node.
<dd>
<dt>
<li> Handle the namespaces.
<dd> Done, for libxml. Added a field to the XMLNode.
<dt>
<li> Support S, at least for the document/tree parser without the
callbacks.
<dd> The callbacks require the driver mechanism used in the CORBA
and Java interfaces to provide mutable state.
<br>
All done, except mutable state. See the interface drivers in S4.
<dt>
<li> Add the contextual information to the function calls.
<dd> Depth, last node, node path, etc
</dl>
<h2>Done</h2>
<dl>
<dt>
<li> Facilities in the XML package to create internal nodes
<dd> PI, comment, etc.
<dt>
<li> as(XMLInternalNode, "character") method
<dd> saveXML() but don't have a document object!
Can we put these into a document and then save and the undo
this document reference.
<br>
Done using xmlNodeDumpOutput()
<dt>
<li> Closing connections from a function or connection argument.
<dd>
Done in R.
<dt>
<li> Allow XML text to be specified rather than treating it as a file.
<dd> Done for libxml parser.
Done for Expat.
<dt>
<li> Call the user level functions in the document parser.
<dd> Done.
<br>
If return <code>NULL</code>, remove from tree (or actually don't
add it).
<br>
Pass in additional information.
<dt>
</dl>
<hr>
<address><a href="http://www.stat.ucdavis.edu/~duncan">Duncan Temple Lang</a>
<a href=mailto:duncan@wald.ucdavis.edu><duncan@wald.ucdavis.edu></a></address>
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Last modified: Thu Jan 31 09:33:05 NZDT 2008
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