Prioritizing Tasks

Tasks within a challenge can be prioritized by challenge managers as high, medium, or low priority. Available higher priority tasks will generally be served to mappers ahead of lower priority tasks. (See below for details about how rules are applied.)

Tasks are prioritized using priority rules that match against either task feature properties (such as OSM tags) or their geographic location. The rules are setup during challenge creation, and can be updated by editing the challenge. Updated rules are immediately reapplied when the edited challenge is saved, but it can take several minutes for that reprioritization process to finish on the server.

In addition, MapRoulette offers an editable “default” priority that will be applied to any task that does not explicitly match any priority rule group. That is, tasks that match neither the configured high, medium, nor low priority rule groups will receive the default priority. If no priority rules are setup, then all tasks will receive the default priority.

Each property-based priority rule is setup with a data type, the name of the property to check, a comparison operator, and a desired property value. For example, a rule setup using string building equals yes would match tasks with a building tag set to yes. The available comparison operators will change depending on the type. For example, an integer type will have numeric operators like > and < whereas a string type will have textual operators like equals and contains.

It is important that the data type on the rule is set correctly for the type of data found on the property.

IntegerWhole numbers
DoubleDecimal numbers
LongReally big whole numbers (> 4 billion)

Multiple rules can be setup as a group for a given priority. Those rules are then either ANDed together (all rules in the group must positively match a task’s properties for the task to be considered a match) or ORed together (any rule in the group must positively match a task’s properties for the task to be considered a match). Furthermore, rules can be nested for greater granularity by choosing the “nested rule” type for a rule.

Note that if a task matches multiple priority groups, it will be assigned the highest matching priority. For example, if it matches both the high-priority and medium-priority rules, it will be assigned high priority

Matching Multiple Tag Values with a Single Rule

If you want to match a single tag against multiple possible values (such as highway equal to either trunk or primary), one option is to setup a separate rule for each value and then OR them together. But MapRoulette offers a shortcut whereby you can include multiple values separated by commas (e.g. string highway equals trunk,primary). When using “positive” operators like equals or contains, the comma-separated values will be OR’d together; when using “negative” operators like doesn't equal or doesn't contain they will be AND’d together (if you require different behavior, then you’ll need to fall back to manually setting up separate rules for each value).

Location Rules

MapRoulette also supports location rules, whereby a task can be prioritized based on whether it falls inside or outside of a bounding box/rectangle. Simply choose location rule for the type, either inside or outside, and then either provide the bounding box explicitly as West,South,East,North or else click the Map button and draw the desired rectangle.

How Rules Are Applied

In general, higher priority tasks will be served to mappers ahead of lower priority tasks. So, until there are no high priority tasks left, mappers working on this challenge will only be served high priority tasks. Then, until there are no normal priority tasks left, mappers will only be served normal priority tasks. Finally, mappers will be served the low priority tasks, until the Challenge’s tasks are exhausted.

Please note that tasks that are marked “Too Hard” with higher priority will still be served before any lower priority tasks. The underlying assumption is that a more experienced mapper will still be able to resolve a task that is marked by someone else as “Too Hard”. We are revisiting this assumption and considering implementing a feature that lets the Challenge author set the number of times a task that is marked “Too Hard” is recycled.

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