Data integrity in shape/dbf files

[Marc JACQUIN - GEOSYS Inc - Minneapolis]

Hi everyone,

Seems to be a great deal to be able to have concurrent updates on shape
files (and dbf).

In an application only using point shapes, I tried to implement record
locking on DBF. I am only using MapServer functions calls to generate
GIF files (from a map file) and embed it into my own CGI. Seems to work
on Win32 with lock functions. On Unix there is an equivalent through
fnctl. I added those functions to the shapelib. Of course, it is only
valid for attributes. Must be careful about dead-locking.

Due to Web browsing, we cannot assure that the end user has an updated
view of the database. There is no way with CGI to know if a page needs
to be reloaded, but when an update is done the CGI can reload the main
page after the post, so the end user sees the changes he did.

Changing shapes cannot really be done with the ismap capabilities. Using
some Java is required. My idea is that shape files and objects can be
stored into a DBMS as BLOB (like SDE does I guess).

Marc
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