specifies the variables in the Activity data set used to identify the lag relationship (lag type, duration, and calendar)
between the activity and its successor. The LAG variables must be character variables. You can specify as many LAG variables
as there are SUCCESSOR variables; each SUCCESSOR variable is matched with the corresponding LAG variable. You must specify
the LAG variables enclosed in parentheses. In a given observation, the ith LAG variable specifies the type of relation between the current activity (as specified by the ACTIVITY variable) and the
activity specified by the ith SUCCESSOR variable. If there are more LAG variables than SUCCESSOR variables, the extra LAG variables are ignored; conversely,
if there are fewer LAG variables, the extra SUCCESSOR variables are all assumed to indicate successors with a standard (finishtostart) relationship.
In addition to the type of relation, you can also specify a lag duration and a lag calendar in the same variable. The relation_lag_calendar
information is expected to be specified as
keyword _ duration _ calendar
where keyword is one of ' ', FS, SS, SF, or FF, duration is a number specifying the duration of the lag (in interval units), and calendar is either a calendar name or number identifying the calendar followed by the lag duration. A missing value for the keyword is assumed to mean the same as FS, which is the standard relation of finishtostart. The other three values, SS, SF, and FF, denote relations of the type starttostart, starttofinish, and finishtofinish, respectively. If there are no LAG variables, all relationships are assumed to be of the type finishtostart with no lag duration. Table 4.3 contains some examples of lag specifications.
Table 4.3: Lag Specifications
Activity

Successor

LAG

Interpretation

A

B

SS_3

Start to start lag of 3 units

A

B

_5.5

Finish to start lag of 5.5 units

A

B

FF_4

Finish to finish lag of 4 units

A

B

_SS

Invalid and ignored (with warning)

A


SS_3

Ignored

A

B

SS_3_1

Start to start lag of 3 units w.r.t. calendar 1
