David -
I think Mike's question is not being understood - I think he is referring to
a .dbf file which is part of a MapInfo table (layer) structure, not a
standalone .dbf file.
Background:
MapInfo supports two table (layer) formats which are fully read-writeable on
all operations, one MI native (.dat) and one dBase III+ (.dbf) (accessible
through File, Save Copy As, Save as Type, dBase DBF (*.tab)). This makes a
MapInfo's table's component files one of the following:
MI NATIVE: MI DBF:
.tab .tab (describes structure of the table, e.g. fields, etc)
.dat OR .dbf (stores the tabular data of the table)
.map .map (stores the graphic objects)
.id .id (cross reference linking the .dat/.dbf to the .map
file)
.ind .ind (if present, index file for fields indexed in
.dat/.dbf)
We have heard from MapInfo support (and others) that their .dat file is
basically a modified .dbf file, so the question is - "why did MapInfo Corp
modify the .dbf into a .dat - why not just use a universally recognized .dbf
file for the tabular data which makes up a table/layer?" Said another way,
what does the .dat do that the .dbf can't?
(I have heard possibilities of the "way" that the .dbf stores integers is
not as efficient as the .dat, but is that the only drawback - the advantages
of a .dbf file format that other software can read (e.g. VB grid controls
can read .dbf) would seam to outway this disadvantage...)
Thanks
Randy
-----Original Message-----
From: David Bruce [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, November 09, 1999 6:32 AM
To: Perry, Mike; [EMAIL PROTECTED]
Subject: Re: MI Native vs. dbf
Mike,
The linkage of database records to map objects is integral
to the GIS
functions in MapInfo [or any other GIS software]. The way
in which
MapInfo implements the linkage - enabling creation,
modifying, and
deleting of object attributes, as well as maintaining
logical database
links to graphic objects which can be created, modified, or
deleted as
well - is a proprietary expansion of the published .dbf file
format.
David Bruce
Pflum, Klausmeier & Gehrum Consultants, Inc.
[EMAIL PROTECTED]
"Perry, Mike" wrote:
>
> If a .DAT is just a slightly modified .DBF that happens to
be larger in file
> size, why does MI use it? What is different about the
native files that
> makes them superior for MapInfo's use?
>
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