AW: AW: [Objectbridge-developers] [Fwd: [objectbridge - Open Disc ussi on] New repository.xml/dtd proposal.]

[Mahler T. <tho...@it...>]

Hi Ivan,

I had a look at your dtd over the weekend I made some minor
corrections/additions. See attached dtd. I also modified the =
repository.xml
accordingly but could not finish it due to lack of time. but you will =
get an
impression...

> -----Urspr=FCngliche Nachricht-----
> Von: Ivan Toshkov [mailto:to...@cr...]
> Gesendet: Freitag, 31. August 2001 16:37
> An: Mahler Thomas
> Cc: objectbridge
> Betreff: Re: AW: [Objectbridge-developers] [Fwd: [objectbridge - Open
> Discussi on] New repository.xml/dtd proposal.]
>=20
>=20
> Hi all,
>=20
> Hopefully, I've changed everything as we discussed, added the missing
> `size' and `nullable' attributes and made the xml a little bit more
> readable.
>=20
> Please review it, to see if there is something wrong or missing.
> Especially with the `ref-id' elements, cause I'm not sure=20
> I've done them
> right.
>=20
> Is it correct that `ReferenceDescriptor/descriptor_ids'=20
> points to fields
> in the current class, and for `CollectionDescriptor/descriptor_ids' =
--
> to fields in the referenced class?
>

yes that's right. I tried to make this even clearer by calling the =
ref-ids
"foreignkey". The foreignkey attribute is always in the table on the =
N-side
of the 1-N relationship.

>=20
> Also, I see that the method
> ObjectReferenceDescriptor.getForeignKeyFields() returns a=20
> list of ids. I
> can preserve it's semantics, but I wonder if this is realy needed.
>=20

It's possible to have compound primary keys. Thus it's also possible to =
have
compound foreign keys.=20

See my changes to your DTD and my comments below

<?xml version=3D"1.0" encoding=3D"UTF-8" ?>

<!ELEMENT mapping-repository ( jdbc-connection+, table+, class+,
class-extent* ) >

<!ELEMENT jdbc-connection EMPTY >
<!ATTLIST jdbc-connection id          ID    #REQUIRED
                          name        CDATA #REQUIRED
                          driver      CDATA #REQUIRED
                          protocol    CDATA #REQUIRED
                          subprotocol CDATA #REQUIRED
                          dbalias     CDATA #REQUIRED
                          username    CDATA #IMPLIED
                          password    CDATA #IMPLIED >

<!ELEMENT table ( column+ ) >
<!ATTLIST table id       ID    #REQUIRED
                schema   CDATA #IMPLIED <!-- we had a schema sttribute =
with
the jdbc-connection,=20
                                             but it has to be assigned =
to
the table.-->
                name     CDATA #REQUIRED
                jdbc-ref IDREF #REQUIRED >

<!ELEMENT column EMPTY >
<!ATTLIST column id      ID    #REQUIRED  <!-- columns need an ID to be
referenced from field decriptors  -->
                 name    CDATA #REQUIRED
                 type ( BIT | TINYINT | SMALLINT | INTEGER | BIGINT | =
DOUBLE
                        | FLOAT | REAL | NUMERIC | DECIMAL | CHAR | =
VARCHAR
                        | LONGVARCHAR | DATE | TIME | TIMESTAMP | =
BINARY
                        | VARBINARY | LONGVARBINARY) #REQUIRED
                 primary-key ( yes | no ) "no"
                 nullable    ( yes | no ) "yes"
                 indexed     ( yes | no ) "no"
                 size CDATA #IMPLIED >

<!ELEMENT class ( extent*, field+, reference*, collection* ) > <!-- a
persistence class must=20
                                                                    =
have at
least one field descriptor -->
<!ATTLIST class name                ID    #REQUIRED
                table-ref           IDREF #REQUIRED
                orderby-field-ref   IDREF #IMPLIED <!-- you ommited the
orderby atribute. it's a reference=20
                                                        to a field
descriptor -->
                conversion-strategy CDATA #IMPLIED
                proxy               CDATA #IMPLIED >

<!ELEMENT extent EMPTY >
<!ATTLIST extent class-ref IDREF #REQUIRED > <!-- we only allow classes =
in
an extend definition that are=20
                                                  explained somewhere =
else
in the repository -->

<!ELEMENT field EMPTY >
<!ATTLIST field id 	ID	#REQUIRED            <!-- we need references
to fields in foreignkey-elements -->
                name 	CDATA 	#REQUIRED
                column-ref IDREF #REQUIRED           <!-- reference to
column element -->
                conversion-strategy CDATA #IMPLIED > <!-- I'd like to =
have a
conversion strategy possible=20
                                                          for =
attributes too
-->

<!ELEMENT reference (foreignkey+) > <!-- renamed the ref-id element -->
<!ATTLIST reference name          CDATA        #REQUIRED
                    class-ref     IDREF        #REQUIRED <!-- reference =
to a
class element -->
                    auto-retrieve ( yes | no ) "yes"
                    auto-update   ( yes | no ) "no"
                    auto-delete   ( yes | no ) "no" >

<!-- thma: renamed ref-id ->
<!ELEMENT foreignkey EMPTY >
<!ATTLIST foreignkey field-ref IDREF #REQUIRED > <!-- reference to a =
field
descriptor that contains a foreign key-->

<!ELEMENT collection ( foreignkey+ ) >  <!-- renamed the ref-id element =
-->
<!ATTLIST collection name             CDATA     #REQUIRED
                     item-class-ref   IDREF     #REQUIRED  <!-- this =
holds a
reference to the item class description -->                  =20
                     collection-class CDATA     #IMPLIED
                     auto-retrieve ( yes | no ) "yes"
                     auto-update   ( yes | no ) "no"
                     auto-delete   ( yes | no ) "no" >

<!ELEMENT class-extent ( extent+ ) >
<!ATTLIST class-extent name CDATA #REQUIRED >


I have a question: What is the scope of an XML ID? The whole xml =
document or
only the enclosing element?
As far as I know they have document scope. thus I had to use fully =
qualified
names in the ID fields (for example for fields and columns), which make =
the
repository quite verbose and redundant.

Do you see any solution to this?

Thomas



> --
> Ivan
>=20