Attributes are absolutely one of the reasons for XML's failure. They seem so innocuous, until you encounter a schema where the developer created:
<Entity ID="12345" Type="Person">
<Property Name="FirstName" Value="Harry" Type="String" />
<Property Name="LastName" Value="Potter" Type="String" />
<Property Name="DateOfBirth" Value="1/1/1980" Type="DateTime" />
</Entity>
Nevermind if you've ever encountered XML with mixed namespaces. Then again, reading the article the bit at the end is exactly the same sort of nastiness.
I imagine if there was discipline around attributes being only used for meta-data and maybe explicit (de-normalized) references (which is arguably meta data, happy to discuss), then XML would be semantically richer by default. However like this we are left guessing the semantics if we encounter some XML.
Somewhat in contrast, HTML is generally, but not consistently, better at making this distinction, which enables clearer semantics around accessibility, HATEOAS and so on. Ironically we are kicking that value proposition into the can when driving web application rendering with JSON (like popular SPA frameworks do), so we have to re-invent meta data and communicate that with JSON-schema.
DTD however, let us not talk about that. Let us just forget it.
I think the drama in XML usage was basically that a simple RPC (or resource query) had at least a dozen namespaces, standards and very long element names. But that is not the fault of XML but of SOAP/WS-*. XML itself can be very beautiful and simple.
Oh, and horrible DOM Apis ;). When working in semi-modern .NET parsing XML/JSON is super easy. Doing the same in JavaScript (out-of-the-box) is a drama.
I see this json schema thing also seems to use long intricate URLs that you can only copy-paste to identify things... at least in this day and age if one does ID with unwieldy blobs, it'd be good to at least use some hash to get the benefits of content addressing.
It even might not matter whether you parse it programmatically or not in some cases. Typically when looking at a given XML (or other data structure text representations) you can pattern match the semantics of what you see, but that is not always true, because everyone uses it in a different way, relying almost completely on schema and documentation to convey semantics, which in turn makes the format strictly inferior to JSON, which also doesn't have rich semantics but is simpler.
As a consequence, JSON in JavaScript is super easy. Using XML is medium-hard.
In .NET using XML or JSON is easy (not super easy).
In C++ using XML or JSON is medium-hard.
Do not know the state of the art for Go, Rust, Java, ...
As a consequence, JSON is - from a JavaScript developer perspective - the holy grail. From a .NET/Java/C++ developer perspective it is just another format.
In Java, there's the JAXB ”parser“ which translates an XML schema into (mostly) straightforward classes. Correct initial setup is the only hard part.
In XML you have to decide if you want DTD or schema enabled (which could provide default values, and could be a security risk) and where abs how you resolve the DTDs from etc. Do you resolve references? And many option options.
So JSON benefits not just from a simpler structure, but also from less optionality.
Basically, in a static typed language you decide for schema checking or not - like for Json -, serializing in structures or access in an API - like for Json.
It is just that JavaScript maps json directly in their dynamic object, array and native types. For xml that is an mismatch. For static languages both are an mismatch.
My understanding is that that's not the case. XML parsers are Pull or SAX based and it's weird as fuck.
You can abstract that out, but parser complexity isn't something to sneeze out. For one thing, parsing XML is notoriously dangerous - tons of vulns both at a design and memory management level.
What about:
- verbosity
- complexity of writing a parser
- complexity of dumping data
- DTDs
- data model which doesn't map directly to a scalar/array/associative array
... and so many other XML features that are either useless or painful just for RPC.
Parser writing and dumping of data is equally complex for both JSON and XML. The only difference is that in JavaScript JSON is so much simpler due to the dynamic nature of the language and the core library. Out-of-the-box XML parsing in JS is just stone-age. Compare that to .NET System.Xml.XDocument and Newtonsoft.Json, then you can see the simplicity how an API could look (in a static type system ;))
No one needs DTDs. No modern contract is every spec'ed in DTDs. XSDSchema has superseeded that 20 years ago. The only issue with it, is that some entry level tutorials are still mentioning it.
The data model mapping depends a lot on the target language. In JavaScript XML is not a match but JSON is. Working with JSON in C++ is equally stupid as working with XML is.
The only stupid feature in XML is namespaces. Without that, it is simple.
Strongly disagree. Sure, you can make XML which is easy to parse, but parsing arbitrary XML is hard. Namespaces (and their short prefixes), and custom entities are something that fly in my face any time I use XML but simply do not exist in JSON.
Dumping is usually OK but again, I've seen XML libraries replace short namespace prefixes with full URLs when dumping, making simple documents unreadable.
JSON however is supported in the language spec
Parsing and walking a JSON structure is much easier and less ambiguous. It's often very clear how to represent/deserialize/serialize JSON (as-is).
The benefits of using schema are clear, you can add validation and semantics to parse (JSON) into a richer and more consistent data structure.
JSON-schema is in large parts a well designed and clear language that is meant to be read and written by humans. Compare that to DTD, XML schema.
I think in terms of raw functionality, there are very strong parallels. And even though I'm not an XML hater, I find JSON simply more pleasant to work with.
The only fundamental advantage that I would give XML over JSON is the fact that you can encode meta data in XML in a more idiomatic, standard way via attributes. But we all know that is not how XML is being used. If the ecosystem around XML wasn't abusing attributes to encode core/primary data, then there would be a stronger argument for the language IMO.