You can add comments to data links
and lookup links.
Comments can also be flagged as important, emphasizing them to anyone
reviewing the DTS.
For example, when links contain complex business logic, it may be helpful
to document this logic directly in the Workbench. Comments provide this
capability.
You can add a comment from the Target pane, the Links tab, the Data
Formulas tab, or the Edit Formula dialog box.
To add a comment to a link:
Select a link on the tab.
Right-click the selected link and select either Edit Data Comment or Edit
Lookup Comment.
The Link Comment dialog box appears.
Note: In the Data Formulas tab, you can also double-click
in the Comments column on each link on which you want to comment.
Type your comment text.
To flag the comment as being
important, check the Flag as important box.
Click OK
to add your comment to the selected link.
In the Comment column of the Data Formulas tab, comments are identified
as one of:
an "ordinary"
comment
flagged as important
To
add a comment to a link from the Edit Formula dialog box
Select a link in the Data Formulas
tab.
Double-click the link. The Edit Formula dialog box appears.
Click Edit
Link Comment. The Link Comment dialog box appears.
Type your comment text.
To flag the comment as being important, check the Flag
as important box.
Click OK to
add your comment to the selected link.
To edit an existing comment
On the Data Formulas tab, double-click
a comment icon in the Comments column.
Edit the comment and click OK when you are finished.
an "ordinary"
comment 
flagged as important