Xml – Representing a graph in XML

graphxml

Hi what will the best possible way to represent a graph in XML, where a node can be the child of a parent node and may be the parent of another child node. It can refer to itself, and multiple nodes can have same parent. And a node can have multiple parents.
All nodes are from same class. I want to build it efficiently, so that if I can learn about a child node from a parent node I can go to the specific child tag without having to iterate all the nodes. Is it possible?
for example here is an overview,

A->B,C,D

B->C,D

it may look like

<Node name=A>
 <childNode name=B>
 <childNode name=C>
 <childNode name=D>
</Node>

<Node name=B>
 <childNode name=C>
 <childNode name=D>
</Node>

So are there any better approaches than this? Whenever I get a child from A i.e. B, than I will have to basically iterate through all Nodes and match there name attribute with B to find the Node that represents B. Can I somehow do it faster?

Best Answer

Since you have a graph, and not a tree as you first thought, why not use GraphML?

GraphML is a comprehensive and easy-to-use file format for graphs. It consists of a language core to describe the structural properties of a graph and a flexible extension mechanism to add application-specific data.

Unlike many other file formats for graphs, GraphML does not use a custom syntax. Instead, it is based on XML and hence ideally suited as a common denominator for all kinds of services generating, archiving, or processing graphs.

XML escape characters

There are only five:

"   &quot;
'   &apos;
<   &lt;
>   &gt;
&   &amp;

Escaping characters depends on where the special character is used.

The examples can be validated at the W3C Markup Validation Service.

Text

The safe way is to escape all five characters in text. However, the three characters ", ' and > needn't be escaped in text:

<?xml version="1.0"?>
<valid>"'></valid>

Attributes

The safe way is to escape all five characters in attributes. However, the > character needn't be escaped in attributes:

<?xml version="1.0"?>
<valid attribute=">"/>

The ' character needn't be escaped in attributes if the quotes are ":

<?xml version="1.0"?>
<valid attribute="'"/>

Likewise, the " needn't be escaped in attributes if the quotes are ':

<?xml version="1.0"?>
<valid attribute='"'/>

Comments

All five special characters must not be escaped in comments:

<?xml version="1.0"?>
<valid>
<!-- "'<>& -->
</valid>

CDATA

All five special characters must not be escaped in CDATA sections:

<?xml version="1.0"?>
<valid>
<![CDATA["'<>&]]>
</valid>

Processing instructions

All five special characters must not be escaped in XML processing instructions:

<?xml version="1.0"?>
<?process <"'&> ?>
<valid/>

XML vs. HTML

HTML has its own set of escape codes which cover a lot more characters.

Python – How to parse XML and count instances of a particular node attribute

I suggest ElementTree. There are other compatible implementations of the same API, such as lxml, and cElementTree in the Python standard library itself; but, in this context, what they chiefly add is even more speed -- the ease of programming part depends on the API, which ElementTree defines.

First build an Element instance root from the XML, e.g. with the XML function, or by parsing a file with something like:

import xml.etree.ElementTree as ET
root = ET.parse('thefile.xml').getroot()

Or any of the many other ways shown at ElementTree. Then do something like:

for type_tag in root.findall('bar/type'):
    value = type_tag.get('foobar')
    print(value)

And similar, usually pretty simple, code patterns.