Preferred Method - Parent Referenced by Children vs Parent Containing Children

[Jake Arkinstall]

Hey guys. I'm just wondering about the preferred method in the following situation.

Say I have a set of categories, with indefinite sub-category levels, for example:

Main Category
    - SubCategory 1
        - SubCategory 1.1
            - SubCategory 1.1.1
            - SubCategory 1.1.2
        - SubCategory 1.2
            - SubCategory 1.2.1
        - SubCategory 1.3
    - SubCategory 2
        - SubCategory 2.1
            - SubCategory 2.1.1
        - SubCategory 2.2
    - SubCategory 3
        - SubCategory 3.1
        - SubCategory 3.2

Each category has a parent and a name, so in a standard database I would have three columns: ID, Name, Parent

However, I know XML is used differently, for example the ability to place an element inside a parent element.

So, which of the following methods would be preferred?

<Categories>
    <Category Name="Main Category" ID="1" Parent="-1" />
    <Category Name="SubCategory 1" ID="2" Parent="1" />
    <Category Name="SubCategory 1.1" ID="3" Parent="2" />
    <Category Name="SubCategory 1.1.1" ID="4" Parent="3" />
    <Category Name="SubCategory 1.1.2" ID="5" Parent="3" />
    <Category Name="SubCategory 1.2" ID="6" Parent="2" />
    <Category Name="SubCategory 1.2.1" ID="7" Parent="6" />
    <Category Name="SubCategory 1.3" ID="8" Parent="2" />
    <Category Name="SubCategory 2" ID="9" Parent="1" />
    <Category Name="SubCategory 2.1" ID="10" Parent="9" />
    <Category Name="SubCategory 2.1.1" ID="11" Parent="10" />
    <Category Name="SubCategory 2.2" ID="12" Parent="9" />
    <Category Name="SubCategory 3" ID="13" Parent="1" />
    <Category Name="SubCategory 3.1" ID="14" Parent="13" />
    <Category Name="SubCategory 3.2" ID="15" Parent="13" />
</Categories>

<Category Name="Main Category">
    <Category Name="SubCategory 1">
        <Category Name="SubCategory 1.1">
            <Category Name="SubCategory 1.1.1" />
            <Category Name="SubCategory 1.1.2" />
        </Category>
        <Category Name="SubCategory 1.2">
            <Category Name="SubCategory 1.2.1" />
        </Category>
        <Category Name="SubCategory 1.3" />
    </Category>
    <Category Name="SubCategory 2">
        <Category Name="SubCategory 2.1">
            <Category Name="SubCategory 2.1.1" />
        </Category>
        <Category Name="SubCategory 2.2" />
    </Category>
    <Category Name="SubCategory 3">
        <Category Name="SubCategory 3.1" />
        <Category Name="SubCategory 3.2" />
    </Category>
</Category>

Thanks,
Jake

[Jake Arkinstall]

Ok, so I take it that both are valid approaches, that the one I'd choose will depend on the situation?

I can see benefits of the latter:

• Grabbing all children of an element should be more efficient.
• Easier for a person to navigate the file
• Searching for an element that has a certain name match and that is under another element would be MUCH easier.

But, with the former, I can't think of that many benefits. So, I suppose I'll be going with the latter!

[cooper.semantics]

With the latter you will also have more control, which is probably what you want

What do you think about this?

<Category Name="Main Category">
    <Category Name="SubCategory 1">
		<Category Name="SubCategory 1.1" />
		<Category Name="SubCategory 1.1.1" />
		<Category Name="SubCategory 1.1.2" />
		<Category Name="SubCategory 1.2.1" />
		<Category Name="SubCategory 1.3" />
    </Category>
    <Category Name="SubCategory 2">
        <Category Name="SubCategory 2.1" />
        <Category Name="SubCategory 2.1.1" />
        <Category Name="SubCategory 2.2" />
    </Category>
    <Category Name="SubCategory 3">
        <Category Name="SubCategory 3.1" />
        <Category Name="SubCategory 3.2" />
    </Category>
</Category>