[
Lists Home |
Date Index |
Thread Index
]
- From: "Bullard, Claude L (Len)" <clbullar@ingr.com>
- To: xml-dev@xml.org
- Date: Fri, 23 Jun 2000 15:24:01 -0500
By the way, just as an addendum. When you use
tools that enable you to generate schemas from
say, relational dbs, tools that reverse engineer
instances can only get you so far. For example,
XML-Spy has a great feature for doing this using
ODBC to connect and get you the table layouts.
However, if a table has no data, it can't, of course,
generate that so it doesn't kick out an instance.
So when you try to generate a schema, you are stuck.
1. Use a test database with sufficient data to
generate the instance. Otherwise, it can't
do anything for that table.
2. Remember that this still won't find key
relationships (primary/foreign).
3. It won't detect duplicates for leaf types
that may be shared across tables. This is a
namespace design decision (tables vs the whole
enchilada in one tree).
4. It makes a good guess about your datatypes,
but for example, where you may have a string
datatype, but in reality, it is an enumeration
(say, a list of states, state codes, etc), you
have to find these and choose your means of
defining these (eg, attribute or elements).
5. It can't really do much about the cardinality
or sequencing. Roughly, these are the required
fields a forms demands be entered and filled
before you can save a record (integrity constraints).
In other words, it can't find what you
are handling semantically in code although
there are other sources (eg, making the forms
dump out information to detect required fields).
If you generate your current relational
schema documents from a database (say into
HTML tables for publication), you may want to
explore using that as a source since it may
have description fields in it that can be
automatically inserted into the new schema
and may contain keywords in the description
that you can use to mark constructs for later
inspection and adjustment.
Len Bullard
Intergraph Public Safety
clbullar@ingr.com
http://fly.hiwaay.net/~cbullard/lensongs.ram
Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h
***************************************************************************
This is xml-dev, the mailing list for XML developers.
To unsubscribe, mailto:majordomo@xml.org&BODY=unsubscribe%20xml-dev
List archives are available at http://xml.org/archives/xml-dev/
***************************************************************************
|