XML Considered Harmful

[Jon Ribbens]

On 2021-09-25, Peter J. Holzer <hjp-python at hjp.at> wrote:
> On 2021-09-24 23:32:47 -0000, Jon Ribbens via Python-list wrote:
>> JSON Schema provides a way to denote composite types.
>
> I probably wasn't clear what I meant. In XML, every element has a tag,
> which is basically its type. So by looking at an XML file (without
> reference to a schema) you can tell what each element is. And a
> validator can say something like "expected a 'product' or 'service'
> element here but found a 'person'".
>
> In JSON everything is just an object or a list. You may guess that an
> object with a field "product_id" is a product, but is one with "name":
> "Billy" a person or a piece of furniture?
>
> I'm not familiar with JSON schema (I know that it exists and I've read a
> tutorial or two but I've never used it in a real project), but as far as
> I know it doesn't change that. It describes the structure of a JSON
> document but it doesn't add type information to that document. So a
> validator can at best guess what the malformed thing it just found was
> supposed to be.

JSON Schema absolutely does change that. You can create named types
and specify where they may appear in the document. With a well-defined
schema you do not need to make any guesses about what type something is.