[Exist-open] Collations

[Wolfgang M. <sb...@we...>]

Hi,

eXist finally supports collations! Sorting and all string comparison operat=
ors=20
have been modified to use a default collation if specified in the XQuery.=20
Also, a specific collation can be defined for each order spec in an "order=
=20
by" clause. The optional collation parameter allowed by most of the string=
=20
functions is not implemented yet, but the default collation will be observe=
d.

I would be happy if users with knowledge in other languages could help to t=
est=20
the functionality. I guess, the languages I speak have rather simple=20
rules ;-) Please have a look at the current CVS or today's snapshot.

The syntax to set the default collation is:

declare default collation collation-uri;

eXist recognizes the following URIs:

1) http://www.w3.org/2004/07/xpath-functions/collation/codepoint

Selects the unicode codepoint collation. This is the default if no collatio=
n=20
is specified. Basically, it means that only the standard Java implementatio=
ns=20
of the comparison and string search functions are used.

2) http://exist-db.org/collation?lang=3Dxxx&strength=3Dxxx&decomposition=3D=
xxx

or just

?lang=3Dxxx&strength=3Dxxx&decomposition=3Dxxx

lang selects a locale. The parameter should have the same form as in xml:la=
ng,=20
for example: "de" or "de-DE" to select a german locale.

strength (optional): value should be one of "primary", "secondary", "tertia=
ry"=20
or "identical".

decomposition (optional): one of "none", "full" or "standard".

I don't really know all the implications of these parameters. Please check =
the=20
Java documentation for java.text.Collator.

Examples:

1) the collation can be specified for each of sort expression in an FLWR:

for $w in=20
("das", "da=DF", "Buch", "B=FCcher", "Bauer", "B=E4uerin", "Jagen", "J=E4ge=
r")
order by $w collation "?lang=3Dde-DE"
return $w

returns:

Bauer, B=E4uerin, Buch, B=FCcher, das, da=DF, Jagen, J=E4ger

Without specifying the collation, it returns:

Bauer, Buch, B=E4uerin, B=FCcher, Jagen, J=E4ger, das, da=DF

2) but it also changes the behaviour of string comparisons:

declare default collation "?lang=3Dde-DE";

"B=E4uerin" < "Bier"

returns "true". If you just use the default codepoint collation, it returns=
=20
"false".

Wolfgang