With normal dependencies, a successor will not become available until 100% of all its predecessors have been scheduled. But there are situations when a successor should become available after only a portion of its predecessors has been scheduled.

An example is in an open cut coal mine, where coal mining can begin as soon as coal is exposed, regardless of whether the block has been fully stripped or not. Release profiles are normally used for short term scheduling, but are also useful for projects that contain large blocks (for example, an open pit subdivided into whole benches).

Release profiles specify the relationship between the quantity of the predecessor that has been mined and the quantity of the successor that has become available (has been released). Usually a certain proportion of the predecessor must be mined before the successor becomes available and thereafter, the quantity of the successor released is proportional to the amount predecessor that has been scheduled.

To allow these complex rules to be established in Autoscheduler projects, each dependency rule set can be assigned a release profile that defines the relationship between the percentage of the predecessor scheduled and the percentage of the successor released.

To assign a release profile to a dependency rule set, the appropriate release profile must be selected from the Release Profile drop down list when the dependency rule sets is being edited. Four pre-defined release profiles have been provided as examples, but user defined release profiles can also be added.

To edit an existing release profile or create a new release profile, the browse button beside the Release Profile drop down list should be pressed. This will display a window containing a list of available release profiles, with buttons to create new profiles or edit, delete and rename existing profiles.

To edit an existing rule, select it in the list and click Edit.

The table on the left of the window lists the data points in the release profile and this is represented graphically on the right. The two columns in the table contain the percentage of the predecessor mined at each point in the profile and the percentage of the successor that will be released (ie become available) at these points. Before the data in the table can be edited, the Allow Modification checkbox must be ticked.

The properties of release profiles are quite straightforward, but they do take some practice to interpret correctly. The graphical representation of the release profile greatly assists with this.

The example shown above (20% Lag Proportional) contains four data points. This profile should be interpreted as follows.

In most situations, records in the database will have several dependencies and some or all of these may have release profiles associated with them. In these situations, the dependency that has released the smallest amount of the successor will be applied.

As an example, consider a record that has two predecessors, both of which have the 20% Lag Proportional release profile described above.

If 50% of one predecessor has been scheduled, but none of the second predecessor, none of the successor will be released. Even though the first dependency will allow 30% of the successor to be mined, the second rule has not released any material and the smallest released quantity is always used.

If 100% of the second predecessor is now scheduled, 30% of the successor will become available. Even though the second predecessor has now released 100% of the successor, the first predecessor will not release more than 30% of the successor.

Even though the many possible interactions between dependencies with and without release profiles may appear complex at first, their application is quite logical. Furthermore, the user is sheltered from the complexities of the interaction between different rules.

Release profiles with upper level dependencies

When release profiles are applied to standard dependency rules, the behaviour of the rules are fairly straightforward. But they can become quite complex when release profiles are assigned to dependency rules that to refer to upper level records.

By default, XPAC will always rationalise dependency rules applied to upper level records to the fewest possible lower level dependencies that would achieve the same outcome.

If a standard release profile is applied to an upper level rule, the release profile will be assigned to each of the lowest level dependencies. The correct trigger quantity must therefore be scheduled from each of the lower level predecessors before any quantity of the successor becomes available. Thereafter, the quantity of the successor that is available will equal the smallest quantity released by the various predecessors.

In the following example, an upper level rule ensure that as an upper level predecessor (containing children A and B) is scheduled, it will release material from the upper level successor (containing children C and D). This rule uses the 25% Lag Proportional release profile. For simplicity we will assume all 4 records contains the same ore quantity.

Because the release profile is applied to each lower level dependency the upper level rule generates, each dependencies release profile will be evaluated independently of the others.

In the example, 60% of record B has been mined which releases 35% of records C and D. But only 40% of record A has been mined and this only releases 15% of records C and D. XPAC will always apply the rule that has released least material when determining how much of the successor record can be scheduled (in this example 15%).

Whilst this approach can be very useful, there are situations where the accumulations of quantity mined and quantity released must be applied directly to the upper level records, rather than to their children individually. The mined quantity would now be considered as the total quantity mined from all the children of the upper predecessor record. The quantity released would also be allocated to the upper level successor, to be shared between all its children in any combination.

When the release profile must be applied in this manner, you can open the advanced Release Profiles dialog box clicking Advanced from the Coordinates tab of any dependency rules sets pane.

Select the Use Upper Level Profiles check box and complete the accumulation fields for each activity the release profile applies to. XPAC applies these profiles independently of one another.

In this example, the material mined from all of the predecessors children is 50% of the total. This value is now used to determine the total quantity of the successors that has been released (25%).

Although the total quantity of the successor is only 25%, this can be shared between the children of the successor in any combination. 50% of record C could be scheduled without any material scheduled from record D. Conversely, 50% of D could be scheduled with C remaining unscheduled. Any combination of threes two extremes could also apply.