ECS Mass, Trait purpose and instantiating entity

Development Programming & Scripting C++
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1

Hi
Currently I am trying to learn Mass system, I understand concepts like Fragment, Tag, Processor, Subsystem, but I am having truble understanding what purpose has Trait. Is some way to encapsulete multiple fragments and tag?
Given code below Trait just encapsulates Fragments and Tag.

void UMoverMassTrait::BuildTemplate(FMassEntityTemplateBuildContext& BuildContext, const UWorld& World) const
{
	BuildContext.RequireFragment<FTransformFragment>();
	BuildContext.RequireFragment<FMassVelocityFragment>();
	BuildContext.AddFragment_GetRef<FMassForceFragment>().Value = StartingForce;

	BuildContext.AddTag<FMSBasicMovement>();

}

I can create manualy Entety by this simple code

		FMassEntityHandle ReserverdEntity = EntityManager->ReserveEntity();
		FLocationFragment location;
		location.position = FVector(Index * 100, 0, 120);
		location.rotation = FVector::ZeroVector;
		EntityManager->Defer().PushCommand<FMassCommandBuildEntity>(ReserverdEntity, location);

In this given example I define entety that has only FLocationFragment and then create it, but what i can do is in simillar fashon add moree Fragments and Tags to given entity.
Can I do simillar thing with traits?
like

UMoverMassTrait.FTransformFragment = FVector();
UMoverMassTrait.FMassVelocityFragment = FVEctor();
EntityManager->Defer().PushCommand<FMassCommandBuildEntity>(ReserverdEntity, UMoverMassTrait);
2

Traits is a way to group related fragments and add dependencies,
for instance if you want to make a Navigation System in Mass, you may depend on the existence of TransformFragment, and also to define your own Fragments etc.

so you Need Traits for that, to let it add Fragments in your entities and to ensure related fragments exists in your Mass Entity, it will give you cool warning to let you that you are missing required fragment if you forgot to add it