Question

Which convention would be preferred and why (include some pros and cons of one over the other)?

This:

<company>
    <employees>
        <employee />
        <employee />
        <employee />
    </employees>
    <buildings>
        <building />
        <building />
    </building>
</company>

or this:

<company>
    <employee />
    <employee />
    <employee />
    <building />
    <building />
</company>

Answer 1

There are no semantic reasons to have explicit representation of the collection through a specific element. In the end, both documents have the same meaning – they represent a company with all of its employees and buildings.

However, there are additional benefits the first example offers:

• it is more readable and can benefit from outlining in editors.
• you can create more strict schema
• it’s easier to serialize to strongly typed collections
• you can specify attributes on the collection element that apply to all elements inside

On the flip side, the second example also has some benefits of its own (though I do find these dubious at least):

• is less chatty/uses less memory
• is easier to process through non-XML tools