Before XML became a standard and given all its shortcomings, what made XML so popular?
One of the major advantages it has over things like CSV files is that it can represent hierarchical data easily. To do this you either need a self-describing tree structure like XML, or a pre-defined format such as SWIFT or EDI (and if you've ever dealt with either of those, then you'll realise that XML is trivial to parse in comparison).
One of the reasons it's actually quite easy to parse is because it's 'bloated'. Those end tags mean that you can accurately match the end of elements to the start and work out when the tree has become unbalanced. You can't do that in the 'lightweight' alternatives such as JSON.
Another reason it's easy to parse is because it has had full support for Unicode encodings from the start, so you don't have to worry about what the default code page is on the target system, or how to encode multi-byte characters, because that information is all contained within the document.
And let's not forget about the other artefacts that came with it like the defined description and validation mechanism (XSD) and the powerful and declarative transformation mechanism (XSLT).
It was the late 90s and the internet was hot hot hot, but companies had systems that couldn't get anywhere near the internet. They had spent countless hours dealing with CORBA and were plotting using Enterprise JavaBeans to get these older systems communicating with their newer systems.
Along comes SGML, which is the precursor to almost all markup languages (I'm skipping GML). SGML was already used to define how to define HTML, but HTML had particular tags that HAD to be used in order for Netscape to properly display a given webpage.
But what if we had other data that needed to be explained? Ah ha!
So given that XML is structured, and you can feel free to define that structure, it naturally allows you to build interfaces (in a non-OO point of view). It doesn't really do anything that other interface languages already do, but it gave people the ability to design their own definitions.
Interface languages like X12 and HL7 existed for sure, but with XML people could tailor it to their individual AIX or AS/400 systems.
And with the predominance of tag language because of HTML, well it was just natural that XML would get pushed to the forefront because of its ease of use.
Straight from the horse's mouth, the design goals of XML were:
- XML shall be straightforwardly usable over the Internet.
- XML shall support a wide variety of applications.
- XML shall be compatible with SGML.
- It shall be easy to write programs which process XML documents.
- The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
- XML documents should be human-legible and reasonably clear.
- The XML design should be prepared quickly.
- The design of XML shall be formal and concise.
- XML documents shall be easy to create.
- Terseness in XML markup is of minimal importance.
The reason why it became popular was because people needed a standard for a cross-platform data exchange format. XML may be a bit bloated, but it is a very simple way to delimit text data and it was backwards compatible with the large body of existing SGML systems.
You really can't compare XML to CSV because CSV is an extremely limited way of representing data. CSV cannot handle anything outside of a basic row-column table and has no notion of hierarchy.
XML is not that hard to parse and once you write or find a decent XML utility it's not difficult to deal with in code either.