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Re: What is this thing that is called a "Data Dictionary?"

From: "Jasbinder Singh Bali" <jsbali(at)gmail(dot)com>
To: "Jim Stalewski" <JStalewski(at)visalighting(dot)com>
Cc: "Richard Broersma Jr" <rabroersma(at)yahoo(dot)com>, "Novice Postgresql-list" <pgsql-novice(at)postgresql(dot)org>
Subject: Re: What is this thing that is called a "Data Dictionary?"
Date: 2007-05-02 21:19:02
Message-ID: a47902760705021419w56cee5f9ka695faf451fa4c80@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-novice
pg_catalog is a system SCHEMA where in you can add your own functions,
operators and types.
However, you can't add your own tables to it. Funny, don't know why though
but that how it is. :)
pg_catalog is indeed a part of PG data dictionary implementation.

~Jas

On 5/2/07, Jim Stalewski <JStalewski(at)visalighting(dot)com> wrote:
>
>
> I think you're right.
>
> I also think that the equivalent in PGSQL may be the information_schema.
> That's what MySQL is trumpeting that they've added to their structure
> that is the same thing as a data dictionary.
>
> It makes sense - information_schema is a standard SQL thing, that was
> introduced back with SQL92.  Oracle uses information_schema too but has
> their own set of "data dictionary" views that apparently are more
> comprehensive ways to access the database's metadata.
>
> Looking at PGSQL's information_schema schema, it does have a lot of that
> kind of thing.
>
> I wonder if pg_catalog and pg_toast also are part of the PGSQL "data
> dictionary" implementation...
>
> ________________________________
>
> From: Jasbinder Singh Bali [mailto:jsbali(at)gmail(dot)com]
> Sent: Wednesday, May 02, 2007 4:00 PM
> To: Jim Stalewski
> Cc: Richard Broersma Jr; Novice Postgresql-list
> Subject: Re: [NOVICE] What is this thing that is called a "Data
> Dictionary?"
>
>
> I think data dictionary is automatically build by the DB.
> Don't think that its a manual task.
> Meta data is always build up automatically by the system intelligently.
> Correct me if I'm wrong.
>
> ~Jas
>
>
> On 5/2/07, Jim Stalewski <JStalewski(at)visalighting(dot)com> wrote:
>
>         I just went to wikipedia.  That's what they say - a data
> dictionary is
>         metadata, and they say that within a DBMS it's represented as a
> set of
>         read-only tables and views.
>         http://en.wikipedia.org/wiki/Data_dictionary
>
>         They seem to indicate it's something that you build, though, not
>         something generated by the RDBMS.
>
>         Innnteresting...
>
>         -----Original Message-----
>         From: pgsql-novice-owner(at)postgresql(dot)org
>         [mailto:pgsql-novice-owner(at)postgresql(dot)org] On Behalf Of Richard
> Broersma
>         Jr
>         Sent: Wednesday, May 02, 2007 3:29 PM
>         To: Jasbinder Singh Bali
>         Cc: Novice Postgresql-list
>         Subject: Re: [NOVICE] What is this thing that is called a "Data
>         Dictionary?"
>
>         Thanks Jas for the description,  it is very helpful.
>
>         Regards,
>         Richard Broersma Jr.
>
>         --- Jasbinder Singh Bali <jsbali(at)gmail(dot)com> wrote:
>
>         > AFAIK, data dictionary is just the metadata (read only set)
> that
>         > contains the definitions of data elements like tables, views,
>         > trigggers, SPs, roles, general DB structuring, space
> allocation
>         > methodology of the DB etc (i mean any data element inside the
> DB).
>         >
>         > It can be viewed as a simple read only file defining the basic
>         > structure of the database actually, in lay men terms.
>         >
>         > Also most of the times, i've observed that its hidden from the
> users
>         > even though its read only. Only DBA should have access to such
> kind of
>
>         > file in secured systems. Thats how we implement it in our
> projects out
>         here.
>         >
>         > Bookkeeping is just synonymous to a data dictionary that would
> not
>         > contain the actual data but would essentially explain the way
> data
>         > would be managed and how.
>         >
>         > I hope this helps.
>         >
>         > Thanks,
>         > ~Jas
>         >
>         > On 5/2/07, Richard Broersma Jr < rabroersma(at)yahoo(dot)com> wrote:
>         > >
>         > > Many of the ERD and SQL books that have have read refer to a
> data
>         > > dictionary.  However, I seem to be missing the point of what
> it
>         > > acuatally is.  IIRC, some books refer to it as a kind of
> document
>         > > created by a DB designer, and other suggest that it is a
> kind of
>         > > RBDMS created metadata.
>         > >
>         > > Can anyone please offer a consise description or provide a
> link to
>         > > that describes what it is?
>         > > Also, how is this information useful to a DBA?
>         > >
>         > > Thanks for the help!
>         > >
>         > > Regards,
>         > > Richard Broersma Jr.
>         > >
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