XML or own-format file?

Question

When is a good idea to save information in a XML file and when in a own-format file?

For XML (or other standard) I see:

• (+) Standard format.
• (-) It's tedious to hand modify.

For own-format files I see:

• (-) We need to build a own-parser (non-standard).
• (+) It can be easy to hand modify the files.

Answer 1

Use XML when it's a good fit in various ways:

• Need to share between different applications which are all capable of handling XML
• Natural tree-like structure
• Primarily data easily represented as text (binary data is a bit of a kludge in text-based formats)
• Extensibility is important
• Performance isn't critical (parsing XML isn't exactly blazingly fast - although if performance is important and you go for XML, shop around for a fast parser, as there's a wide difference between fastest and slowest)
• Schema can be pre-defined and documents can be verified against it
• Simpler formats (e.g. name=value pairs) don't cut it

Basically if there's a pretty natural representation of your data model in XML, that may well be the easiest way of handling it. If you'd end up having to mess around a lot to fit it in with XML, think about other formats. Note that there are plenty of other standard (or "somewhat standard" - e.g. supported by tools on multiple platforms) formats available beyond just XML.

Answer 2

For XML I see:

• (+) Standard format.

• (-) It's tedious to hand modify.

  I only use XML when the API requires it.

For JSON/YAML I see:

• (+) Standard format.

• (+) It's easy to hand-modify.

  I use JSON/YAML for almost everything. Except when an interface requires something else.

For CSV I see:

• (+) Standard format.
• (+) It's easy to hand-modify.

• (-) It's a little murky when the column names are screwy or data isn't in simple first-nromal form.

  I use CSV whenever possible.

For Language Serializers I see:

• (+) Standard format for the given language.

• (-) nearly impossible to hand-modify.

  I use serialized files once in a while to pass data among processes when I'm sure both sides are in the same language.

For own-format files I see:

• (-) We need to build a own-parser (non-standard).

• (+) It can be easy to hand modify the files.

  I avoid inventing my own file format. Haven't invented my own file format in years.