Serialize functions: consistency

[ChristianGruen]

We should be more ambitious about ensuring consistency when serializing data back to its original representation, and how to achieve it. This is the status quo:

Format	Serialize Function	Parse Function
XML	fn:serialize($input)	fn:parse-xml
JSON	fn:serialize($input, map { 'method': 'json' })	fn:parse-json
JSON	fn:xml-to-json($input)	fn:json-to-xml
XHTML	fn:serialize($input, map { 'method': 'xhtml' })	fn:parse-html
HTML	fn:serialize($input, map { 'method': 'html' })	fn:parse-html
CSV	still missing	fn:parse-csv and variants

In BaseX, the XML created by fn:json-to-xml can already be serialized back to JSON as follows (related: #759):

serialize(
  <map xmlns="http://www.w3.org/2005/xpath-functions">
    <number key="A">1</number>
  </map>,
  map { 'method': 'json', 'json': map { 'format': 'basic' }
})

For CSV, we’ve introduced a CSV serialization method that supports all CSV flavors we support (see CSV Module for more details):

serialize(
  <map xmlns="http://www.w3.org/2005/xpath-functions">
    <number key="A">1</number>
  </map>,
  map { 'method': 'csv', 'csv': map { 'format': 'direct' }
})

Related (parse functions): #748

[ndw]

What is the actual proposal?

[ChristianGruen]

Greetings to Prague… The proposal could be twofold:

1. introduce a csv serialization method;
2. add a serialization parameter for the existing json method to serialize the result of fn:json-to-xml back to JSON.