Comparison Date

It is only by comparing a drawing at two states or sessions that it is possible to determine what has changed. Using the current state of the drawing as one state we must then reference an earlier state in order to make the comparison. We do this by specifying a Comparison Date (COMPDATE), that is, the drawing state at a time that we wish to use as a baseline or datum.

The Comparison Date can be set in one of two ways:

• By specifying an actual time and date.

• By referencing a Stamp.For example:

  Example:
  SETCOMPDATE 31 March 2002 SETCOMPDATE STAMP /Prelim-Milestone

The current Comparison Date can be queried by:

Q COMPDATE DATE

Q COMPDATE STAMP

A Stamp is a way of referencing combinations of databases and sessions at specified instances. Stamps are created by the Marine Administrator. For further information on Stamps and how they are created and used refer to the Administrator Command Reference Manual and the Administrator User Guide.

The Comparison Date can be used in queries on any attributes, using the syntax OLD. For example:

Q OLD XLEN

will output the value of attribute XLEN of the current element at the Comparison Date.

Q OLD REF OF /OLDPIPE

will output the reference of deleted element /OLDPIPE at the Comparison Date.

for further information on the Comparison Date functionality refer to the Admin User Guide.