XML is not human readable

Over the last couple of weeks I've heard the same phrase said by about five different people

The advantage of XML is that its human readable, this is why Web Services are better than previous technologies.

Now I'm not going to get in a readability of WSDL v IDL (hint: the winner isn't WSDL). But I think its worth examining the whole concept of XML and whether it should be human readable, particularly when it comes to business processes, service descriptions and service contracts.

So should a "good" Web Service description be human readable? Lets examine the purpose of that description

1. To enable consumers to call the service correctly
   
2. errr... that is pretty much it
   

So given that goal what is the best way to show this to both systems and to people? The answer is of course to have a common technical language that enables accurate exchange, and then have this rendered for different types of people and systems, so Java code turns into "Java", C# turns it into C# and for people it gets rendered into a nice picture that shows the methods and the constraints.

WSDL and BPEL (especially BPEL) are examples of that technical language. There was never a goal for them to be human readable, they are aiming to be machine readable. The Geo Ripping wsdl is a very simple self contained example as to why XML isn't designed for humans to read.

Sure when it comes to debugging you can print out the XML and a skilled person can spot some of the errors, but then you could do this with RMI, CORBA, DCOM and even C (using a hex editor in the later case) but the idea of "human readable" is that anyone could read the SOAP messages or BPEL process context, and this 100% isn't true.

Or to look at it another way....

XML is not human readable, its not designed to be human readable and you shouldn't try and make it human readable. Just because something is in Unicode doesn't mean that anyone can read it. French, Chinese, Klingon (WTF?), Japanese, German, English, Urdu and many other languages can be written in Unicode, and XML should be viewed in the same way but as a language with lots of unrequired syntax, no real semantics and pretty random grammar in general.

Think of XML as being English spoken by a sulky French teenager, lots and lots of grunts that mean nothing to anyone and the occasional fragment of something that no-one actually properly understands.

Reading BPEL is like trying to understand a conversation between a sulky French teenager and a sulky American teenager... in Chinese when they've only had two lessons and you don't speak Chinese.

XML is as hum

Technorati Tags: SOA, XML,Service Architecture