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| The CPM Procedure |
| SUCCESSOR Statement |
- SUCCESSOR variables / lag options ;
- SUCC variables / lag options ;
The SUCCESSOR statement is required when data are input in an AON format. This statement specifies the variables that contain the names of the immediate successor nodes (activities) to the ACTIVITY node. These variables must be of the same type and length as those defined in the ACTIVITY statement.
If the project does not have any precedence relationships, it is not necessary to use the SUCCESSOR statement. Thus, you can specify only the ACTIVITY statement without an accompanying SUCCESSOR statement.
If the precedence constraints among the activities have some nonstandard relationships, you can specify these using the LAG options. The following is a list of LAG options.
- ALAGCAL=calname
specifies the name of the calendar to be used for all lags. The default value for this option is the DEFAULT calendar.
- LAG=variables
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 (finish-to-start) 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 finish-to-start. The other three values, SS, SF, and FF, denote relations of the type start-to-start, start-to-finish, and finish-to-finish, respectively. If there are no LAG variables, all relationships are assumed to be of the type finish-to-start with no lag duration. Table 4.19 contains some examples of lag specifications.
Table 4.19 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
- NLAGCAL=
calnum specifies the number of the calendar to be used for all lags. The default value for this option is the DEFAULT calendar.
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