Hierarchical query

[Vadim Tropashko]

Reposting with more clarification (as Jan asked).

Suppose I have a BNFgrammar and a source text parsed into a tree. How
would I query an
identifier declaration?

All the XQuery tutorials (where I went to gather some ideas) start
with simpleminded examples like browsing all the descendants of /
bookstore/book (and the bookstore XML design is such wrong idea to
boot).

Perhaps some example is needed. A simplified grammar:

statement_block :
'declare'
declaration_ite m_list
'begin'
statements
'end'
;

statements:
(statement_bloc k | assignment) statements |
;

assignment:
identifier ':=' (identifier | number) ';'
;

declaration_ite m_list:
identifier 'integer' ';'
;

Suppose we parse the following text

declare -- token #1
i integer; -- tokens 2,3,4
begin
i := 1; -- tokens 6,7,8,9
end;

So that we get the derivation tree like this:

1 statement_block
1.1 'declare' (matches token #1)
1.2 declaration_ite m_list
1.2.1 identifier (matches token #2)
1.2.2 'integer' (matches token #3)
1.2.3 ';' (matches token #4)
1.3 'begin' (matches token #5)
1.4 statements
1.4.1 assignment
1.4.1.1 identifier
1.4.1.2 ':='
1.4.1.3 number
1.4.1.4 ';'
1.4.2 statements (matches empty token)
1.5 'end';
Now, given a derivation tree and the leaf node identifier 1.4.1.1
corresponding to the token #6 which is variable i, how do we find the
node 1.2.1 that declares it?

[Marshall]

On Jun 13, 4:47 pm, Marshall <marshall.spi.. [e-mail] e:

>
My hope is that this post will stimulate an educated and informative
discussion of the relative merits of different approaches to
tree traversal, not neglecting to differentiate among the needs
of diverse use cases.

Hey, it could happen.

Or, you know, not.
Marshall