Evaluation level and evaluation type

When defining principal fields in XECUTE, you can choose how and when expressions are evaluated during reserving calculations. These settings—Evaluation Level and Evaluation Type—determine whether calculations occur at the block level or after aggregation into slices, and whether they apply to the entire slice or per material.

Choosing the right configuration depends on the level of detail you need for reserving, scheduling, and reporting.

Evaluation level

The Evaluation Level specifies the stage at which an expression is applied:

Block (default): The expression is evaluated for each block in the block model. Results are then aggregated according to the field’s Aggregation Type (e.g., Sum, Weighted Average).

Use case: When you need precise block-by-block calculations, such as adjusting grades or densities before aggregation.
Slice: The expression is applied after blocks are aggregated into slices. This allows calculations to use slice-level attributes, such as PlanArea or AvgThk, which are not available at the block level.

Use case: When calculating drill metres or applying logic based on slice geometry.

Evaluation type (slice-level only)

When Evaluation Level is set to Slice, you can refine how the expression is applied:

Slice Total Expression: The expression is applied once per slice, using aggregated values for all materials in that slice.

Example: Calculating a value based on PlanArea and AvgThk for the entire slice.
Material-Based Expression: The expression is applied separately for each material within the slice.

Example: Applying different drill spacing for waste vs ore materials.

How evaluation level and type affect results (example)

To understand how Evaluation Level and Evaluation Type work, let’s look at an example using a custom field called auTest. This field uses an expression that simply returns the value of the Au (gold grade) field. The Aggregation Type is set to Max so it returns the maximum value.

We’ll compare how the result changes depending on the evaluation settings.

Principal Field (Au)
Code	Au
Description	Gold Grade
Category	Dig
Units	ppm
Field Type	Number
Aggregation Type	Max
Decimal	2
Default Value	1
Expression	No (value derives from block model)

The original Au principal field configuration

Principal Field (AuTest)
Code	2.66
Description	Gold Grade Test
Category	Dig
Units	ppm
Field Type	Number
Aggregation Type	Max
Decimal	2
Default Value	1
Expression	[Will change depending on each scenario below]
Evaluation Level
Evaluation Type

The AuTest principal field configuration

Block level

Principal Field (AuTest)
Expression	Au (gets the original Au value)
Evaluation Level	Block
Evaluation Type	N/A

At the Block evaluation level, the expression is applied to each individual block in the block model. (The expression gets the original weight averaged Au value of each block). After that, the aggregation type (in this case, Max) is applied across all blocks in the activity area. This means the result will be the highest single block value in the area.

The image below highlights the block within the activity area with the highest grade. The activity area’s AuTest field inherits that value.

Viewing the attributes of a single block (at the green arrow) within an activity area. The highlighted block and tooltip are of the block with the highest gold grade.

Activity Area	Activity	Pit	Au	auTest	Mining Level
DIG_010	Mining	East Pit	0.48	0.86	10m Benches - 1110

Various fields of the activity area. The auTest field is 0.86: it gets the maximum Au value of a block within the activity area – because it’s aggregated at the block level.

Slice level – Material-based

Scenario: although material-based, each material uses the same expression

Principal Field (AuTest)
Evaluation Level	Slice
Evaluation Type	Material-based
Material Expressions
HGOx Expression	Au (gets the original Au value)
HGSx Expression	Au
LGOx Expression	Au
LGSx Expression	Au
NAG Expression	Au
PAG Expression	Au

When using Slice level with Material-Based evaluation, the blocks are first grouped into slices. Within each slice, the expression is applied separately for each material. Then, the aggregation type is applied across all slices. Because values are averaged within slices before aggregation, the result is usually lower than the block-level result.

In this example, to determine an AuTest value, the software gets the Au value of blocks, for each material in each slice, then does the Max aggregation (returning the maximum value of the slices). The slice highlighted below (red) has the highest weight average Au – but it’s less than the block evaluation example because it’s evaluated over two blocks.

The highlighted slice has the highest weight average Au grade of all slices in the activity area.

Activity Area	Activity	Pit	Au	auTest	Mining Level
DIG_010	Mining	East Pit	0.48	0.8193	10m Benches - 1110

Because there are fewer slices in the activity area, each one covers a larger area and includes more blocks. This often brings in blocks with lower Au values (like the green block in the upper left), which reduces the overall value after aggregation (the maximum in this case)

Activity Area	Activity	Pit	Au	auTest	Mining Level
DIG_010	Mining	East Pit	0.48	0.7885	10m Benches - 1110

Scenario: Each material uses a different expression

In this other scenario, each material within a slice uses its own expression.

Principal Field (AuTest)
Evaluation Level	Slice
Evaluation Type	Material-based
Material Expressions
HGOx Expression	1
HGSx Expression	2
LGOx Expression	3
LGSx Expression	4
NAG Expression	5
PAG Expression	6

For example, PAG is assigned a value of 6, while other materials have different constants. The expression is evaluated per material in each slice, and then the Max aggregation is applied across all slices.

Because PAG appears in at least one slice, its value (6) becomes the maximum for the entire activity area even if other slices contain lower values.

Activity Area	Activity	Pit	Au	auTest	Mining Level
DIG_010	Mining	East Pit	0.48	6.0000	10m Benches - 1110

Slice level – Slice total

When you choose Slice Total, the blocks are grouped into slices, and your expression (for example, referencing the original Au field) is applied once per slice using all blocks in that slice. It does not calculate separately for each material. After that, the chosen aggregation type (such as Max) is applied across all slices.

Examples

Pincipal Fields \ Au

Principal Field (AuTest)
Expression	Au
Evaluation Level	Slice
Evaluation Type	Slice Total

The expression returns the weight-averaged Au value for all blocks in each slice, then aggregates the slices using Max.

Material Fields \ LGSx_Au

Principal Field (AuTest)
Expression	LGSx_Au
Evaluation Level	Slice
Evaluation Type	Slice Total

The expression returns the weight-averaged Au value for all blocks of the LGSx material in each slice, then aggregates using Max. As expected, the maximum Au is lower because it only considers the lower-grade material.

Area Fields \ Area_Total_Au

Principal Field (AuTest)
Expression	Area_Total_Au
Evaluation Level	Slice
Evaluation Type	Slice Total

The expression returns the weight-averaged Au value for all blocks in the entire activity area. This is effectively the same as the block-level aggregation for the Au field.

Summary of expression field availability

This table and quick list below explain which field categories you can reference when building expressions for principal fields, based on the field’s configuration. They shows how Aggregation Type, Evaluation Level, and Evaluation Type affect the availability of different field categories (such as Principal Fields, Name Fields, Material Fields, and Area Fields) and whether spatial fields (like PlanArea or AvgThk) can be used.

Quick guide

Block level (any aggregation)

You can use Principal Fields and Name Fields.
Spatial fields (PlanArea, AvgThk, etc.) are not available.

Slice level – Slice total expression

You can use Principal Fields, Name Fields, Material Fields, and Area Fields.
Spatial fields are available.

Slice level – Material-based expression

You can use Principal Fields and Name Fields.
Spatial fields are not available.

Aggregate

You can use Principal Fields and Name Fields.
Spatial fields are not available.
Cannot be used in objectives or Product Optimiser.

Full table

Aggregation Type	Evaluation Level	Evaluation Type	Field Category Available	Spatial Fields Available?	Notes
None, Sum, Min, Max, Weight Average	Block	N/A	Principal Fields, Name Fields	N/A	Only Sum and Weight Average types can be used in objectives.
None, Sum, Min, Max, Weight Average	Slice	Material-Based and Slice Total expression	Principal Fields	Only for Slice Total Expression evaluation type	Slice evaluation level fields are not available for use in objectives.
None, Sum, Min, Max, Weight Average	Slice	Material-Based and Slice Total expression	Name Fields	N/A
None, Sum, Min, Max, Weight Average	Slice	Slice Total expression	Material Fields	N/A
None, Sum, Min, Max, Weight Average	Slice	Slice Total expression	Area Fields	N/A
Aggregated Evaluation	(Evaluated at level used)	N/A	Principal Fields, Name Fields	No	Aggregated Evaluation fields are not available for use in objectives.