Yes, this is a pretty readable code. I don't understand it deeply, but it's clear that it's a definition that defines some filter that I can call by its id. Wh

Yes, this is a pretty readable code. I don't understand it deeply, but it's clear that it's a definition that defines some filter that I can call by its id. What seems to be a hierarchy comes from the fact that this is a serialization of the data and the serialization has to be sequential and thus you cannot have a true graph here, only a tree with references. This would be true for any serialization format. Once you deserialize this into your internal format you can have back your graph and it can be as efficient as you'd like. As a serialization format, however, it's very good, because it's based on a good standard. What's especially good about it is that you can see through its structure and access parts of it using the same generic API as with other XML-based formats. For example, in the browser you can style SVG with the same styling you use for HTML or script it with JavaScript.