> ## Documentation Index
> Fetch the complete documentation index at: https://docs.activeviam.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Level Configuration
This guide aims at providing the basic configuration tips to start defining levels with the fluent builder.
## Introduction
Hierarchies categorize data into levels for aggregation and visualization. For more info about hierarchies,
see [here](../concepts/dimensions_and_hierarchies).
* The levels in a hierarchy are organized with parent-child relationships.
* All non-slicing hierarchies have a parent level, called "AllMember", to aggregate data across all members of all
levels. It is created and configured automatically.
* The level is often based on a column of the database from which they inherit a data type, a formatter and a
comparator.
## Basic configuration
For a hierarchy, use:
* `withDimension("dimensionName")` to define the dimension
* `withHierarchy("hierarchy)` to define a hierarchy
* `withLevel("levelName")` to define the levels.
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
builder.withDimension("Time").withHierarchy("Time").withLevel("year").withLevel("month");
```
Here the order is important : the level "year" is defined first so it will be the parent of the level "month".
Several shortcuts are provided by the builder.
For example, define a dimension, with one hierarchy and one level, all with the same name, with
`withSingleLevelDimension("dimensionName")`:
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
StartBuilding.cube()
.withName("Cube")
.withDimensions(builder -> builder.withSingleLevelDimension("Currency"));
```
The level is based on the first reachable field, with the same name, in the database. The level inherits the data type
and other properties from the field.
Specify a field name after the level name to:
* Create a level with a different name to the selection field
* Create a level that is based on a specific selection field (i.e. not the first reachable field with the same name as
the level)
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
builder.withDimension("Trader").withHierarchy("Trader").withLevel("Trader", "Trader_id");
```
## Defining the time levels
### Level types
There are mainly three level types:
* `ALL` the type of the "AllMember" level that exists as the first level of all [non-slicing hierarchies](./hierarchy_configuration#hierarchy-members-allmember-vs-slicing-members)
* `TIME` for time levels (with specific subtypes for the different time units)
* `REGULAR` for the other levels (it is the type defined by default).
The level type is different from the data type of the selection field the level is based on. The data type is the type
of the members of the level: double, string, date...
Use `withLevelType(ILevelInfo.LevelType.TIME)` to define the type of the levels representing time so that they are
correctly handled by time measures (for example, finding the first month of a quarter).
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
builder
.withDimension("Time")
.withType(IDimension.DimensionType.TIME)
.withHierarchyOfSameName()
.withLevel("Time")
.withType(ILevelInfo.LevelType.TIME);
```
### Formatter
By default, each data type has a formatter to define how to display the level members:
* add a comma to group thousands in numbers
* format dates
Simple formatter can be used with their string representation:
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
builder
.withDimension("Time")
.withType(IDimension.DimensionType.TIME)
.withHierarchyOfSameName()
.withLevel("year")
.withFormatter("DATE[MM-DD-YY]");
```
To define a custom formatter, see [this page](../configuration/internationalization#formatter-factory).
## Ordering level members
By default, members of a hierarchy are ordered:
* Alphanumerically for data with type string
* Chronologically for dates
The order of the level members affects
* the order in which the members are displayed on the dashboard.
* the level member selected for some commutations (such as lag and lead measures).
### First objects
To fix the first objects so they always appear on top, use `withFirstObjects`:
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
builder.withSingleLevelDimension("Currency").withFirstObjects("USD", "EUR", "GBP");
```
### Custom comparator
To define the comparator of a specific level, use `withComparator(key)` where `key` is one of the following:
* the plugin key of a built-in comparator provided by Atoti Server, see constants defined in `IComparator`.
* the plugin key of a custom comparator implementation.
Comparator classes should implement the `IComparator` interface which wraps a `java.util.Comparator` into a plugin
value for easier configuration.
Custom comparators are typically defined as follows:
```java theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
@AtotiExtendedPluginValue(key = MyComparator.PLUGIN_KEY, intf = IComparator.class)
public static class MyComparator implements IComparator