Dependencies are used in different ways in a schedule, depending on the type of resources that are assigned to your scenario. Click on the relevant resource type below for further information on how they use dependencies.

Input path - production rate resources

For resources that have the mining sequence set to an Input Path and the resource capacity set to Production Rate, the dependencies are only used if you specifically request it. This request is made by ticking the option called Obey Dependencies and Precedences, which is on the Production Details item in the schedule setup tree for each resource.

Obey dependencies and precedences

If this option is not ticked, then the input path for the resource will be followed without regard for the dependencies or the precedences. The dependencies and precedences may therefore not be obeyed in the schedule. A report can be generated to indicate when and where these rules have been broken and this is called the Schedule Checker report.

If this option is ticked, then the resource will try to follow the input path, however it will also obey the dependencies and precedences. For example, if the next record to schedule in the input path is not available (ie. its dependencies have not been satisfied), then it will not be mined. Another user-defined option is used to determine what happens in this situation. This option is also on the Production Details item in the schedule setup tree for each resource and it is called Enable Look Ahead.

Enable look ahead

If this option is not ticked, then a delay will be inserted in the output path until that record is available for scheduling. This delay is a non-productive activity that is selected from a drop down list, also on the Production Details item. It is called the Delay Activity. Each time another record is scheduled (eg. by another resource), the record in the input path will be assessed to see if it is available yet. As soon as it becomes available, the delay will be finished and the record swill be scheduled.

If this option is ticked, then the unavailable record will be left and XPAC will look ahead to the following record in the input path and assess its mining potential. If it is found that there are no records in the input path which are available, then the Delay Activity will be inserted. Each time another record is scheduled (eg. by another resource), the records in the input path will be assessed (in order) to see if they are available yet.

Input path - target resources

For resources that have the mining sequence set to an Input Path and the resource capacity set to Target, dependencies and precedences cannot be used to control the schedule sequence. The dependencies and precedences that you set up may therefore not be obeyed in such schedules. However, a report can be generated to indicate when and where these rules have been broken and this is called the Schedule Checker report.

Autoscheduler resources

For resources that have the mining sequence set to AutoScheduler and the resource capacity set to either Production Rate or Target, the dependencies are used to specify unacceptable mining sequences. Schedules generated by the AutoScheduler will always obey the dependency and precedence rules.

The AutoScheduler uses the Available Block List (ABL) to ensure each record in the database is not scheduled until it has become available. If a block does not have any dependencies it is immediately available for mining and all such blocks are placed in the ABL before scheduling begins.

Blocks that have at least one dependency are not placed in the available block list at the start of the schedule, preventing them from being selected. However, they are re-evaluated every time an available block is scheduled and are added to the ABL once all of their dependencies have been satisfied.

Because a block has been placed in the available block list does not mean it can actually be scheduled; another scheduling rule, such as a period or capacity constraints may have temporarily made it unavailable for mining. As the AutoScheduler will only select blocks from the available block list, the dependency rules are always honoured for these types of resources.