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   RE: SQL Schema to XML Schema generator [any out there?]

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  • 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

Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h

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