ansaurus

Question

How to make an XML document which contains relationships?

Answer 1

+2 A:

You're missing a root element, such as:

<?xml version="1.0"?>
<companies>
    <company>...</company>
    <company>...</company>
</companies>

Otherwise I think this structure is fine for representing a one-to-many relationship of companies' employees.

In response to the USGS feed you posted, it does have a root element, feed.

Ben James 2010-01-26 09:57:42

updated my question... are you sure about that root element thing? Apple's XML doesn't have it and works... confusing

openfrog 2010-01-26 10:20:23

There is a root element, it is `feed`

Ben James 2010-01-26 10:36:22

I see... so the root element has nothing to do with "there are many companies, so they need a root"...because then this would also apply to employee inside companies, and so on...

openfrog 2010-01-26 11:45:55

Answer 2

+1 A:

You might also consider combing the previous example while having name as an attribute, like so:

<?xml version="1.0"?>
<companies>
    <company name="Apple">
        <employee>Steve</employee>
        <employee>Bill</employee>
    </company>
    <company name="Banana">
        <employee>John</employee>
        <employee>Luke</employee>
    </company>
</companies>

PatrickJ 2010-01-26 10:05:34

Answer 3

A:

You should NOT rely on naming. You should give each employee an id (the same for the company). Because otherwise you cannot have two employees with the identical name.

Example:

<data>
    <company id="0">
      <name>Apple</name>
      <employee>0</employee>
      <employee>1</employee>
    </company>
    <company id="1">
      <name>Banana</name>
      <employee>2</employee>
      <employee>3</employee>
    </company>
    <employee id="0" name="Steve"/>
    <employee id="1" name="Bill"/>
    <employee id="2" name="John"/>
    <employee id="3" name="Luke"/>
  </data>

Karussell 2010-01-26 10:08:19

Answer 4

+1 A:

XML wasn't really made for data modeling. It was made for data serialization. It's better to model using ER diagrams and think of the XML representation only after you've decided on the data model.

Generally, when your relationships form a tree, you can model them with subelements. When they don't, you may prefer to introduce references of some kind. For instance, in this case, including employee elements into company elements will suffice as long as every employee is associated with exactly one company. But if the same employee has to be listed for multiple companies you'll start duplicating data. To avoid that, including references from one element to another may be preferable.

XML technology has some support for references (e.g. you can use IDs and IDREF attributes and verify their correct use with a DTD) but not much, and it certainly doesn't tell to you how and where to use such references.

reinierpost 2010-01-26 10:34:32

ansaurus

tags:

views:

answers:

How to make an XML document which contains relationships?

related questions