DortDB - XQuery

This package is a language plugin for DortDB. It adds support for XQuery queries.

Data adapter

The default data adapter implementation allows queries against DOM and XML data structures. It also allows accessing JS object properties with the attribute axis (obj/@prop).

Differences between DortDB and XQuery

The DortDB XQuery implementation does not include any typing except cast expressions. This means that the following is not (and is not ever planned to be)
available:

- as keyword
- typeswitch expressions
- treat expressions
- instance of expressions
- castable expressions
- validate expressions
- any function types except function(*)
- function references containing arity information (fnname#arity)

The following is also not implemented, but may be added in the future:

- try catch expressions
- pragma expressions
- window FLWOR clause
- inline functions
- %private and %public modifiers
- any module prolog except namespace definition

Custom plan operators

XQuery specific operators

XQuery extends the DortDB unified algebra with the following operators:

| name | signature | schema | description |
| -------------- | ------------------------------------------------- | ------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| projectionSize | $\text{size}(\texttt{name}, \texttt{source})$ | source + (name) | Adds attribute name to each tuple from source containing the total count of tuples in source. |
| treeJoin | $\text{treeJoin}(\texttt{expr}, \texttt{source})$ | source + (dot, pos, len) | Similar to projectionConcat, but expr generates items instead of tuples. Also adds attributes for xquery context: current item, ordinal index and total item count. |