>How do I know with the "id=200" that 200 is an int rather than a byte or string?
Field (of database) and attribute (of tag) are put into one-to-one
correspondence.
Thus datatype of attribute is datatype of field (which is specified
during "create table" or "alter table").
>how do we add the new table?
by DDL, of course.
TML don't create/alter/drop table/index.
>accesses to a database want to retrieve a simple tree
It's difficult to bring inverse example - when it's necessary to get
records of only one table. Really, in life (not in math problems).
>your alternative access method doesn't let me grab "nets" (directed graphs, possibly cyclic)
Yes.
You must inquere records of two tables (nodes and bonds) separately.
>> After that, look at source of server programs, servicing this databases.
>> These programs get part of net (not part of one table!, not part of
>> joined tables! not part of one view!) and put it into program-visualizer.
>Also not trees (necessarily)
No. Server program inqueries tree (as part of graph).
>why you just don't write this as a simple php/perl/ruby/whatever script?
Not me.
Not programmer.
I speak about appied specialists (physicists, biologists, etc), which
can NOT do that.
Join of SQL and php (using libraries) is problem for them.
>it's just an afternoon's work
Not for mentioned people.