Existence periods

Most elements in 4HSE can have existence periods: they say when — for how long, and how often — that element was part of your safety project.

When they do not apply

Some elements are intrinsically tied to a date or a fixed interval, so a period would mean nothing: the edition of a course, a medical examination, a certificate.

The typical case: seasonal work

Take an employee, Mario Rossi, who worked in two distinct periods: from 1 October to 1 December 2019, and then from 1 January 2020 on an indefinite contract.

	Start	End
Period 1	01/10/2019	01/12/2019
Period 2	01/01/2020	+infinite

During his employment he was assigned to a work phase, attended two courses, and received a high-visibility vest. Those elements are children of the person, who is their parent:

+ Mario Rossi
  |_ Warehouse management
  |_ Forklift operator training
  |_ General training
  |_ High-visibility vest

This parent–child structure recurs throughout 4HSE, and it is what makes inheritance work.

Why inheritance matters

By default an element has an infinite lifespan. But an element with no period of its own implicitly inherits the periods of its parent.

So the courses Mario attended cannot exist outside the time he was employed, without anyone having to say so. If you never set a period on them, they last exactly as long as he does.

This is what keeps the data honest: a certificate cannot silently outlive the employment it belongs to, and a worker’s history does not have to be maintained in two places.

Say his four child elements have these periods:

Element	Start	End
Warehouse management	15/10/2019	30/11/2019
Forklift operator training	05/10/2019	15/11/2019
General training	inherited from Mario Rossi	inherited from Mario Rossi
High-visibility vest	10/10/2019	30/11/2019

Three of them have periods of their own. General training does not, so it inherits Mario’s — and any child added later will do the same.

The rules

Rule
Default	an element has an infinite lifespan, from minus infinity to plus infinity
Implicit inheritance	an element with no period of its own inherits its parent’s, when the parent has one
Containment, upwards	for every period of the current element there must be at least one parent period containing it
Containment, downwards	for every child period there must be at least one period of the current element containing it

4HSE enforces these constraints as you add or edit periods, so the hierarchy stays consistent.

What the chart shows

The chart shows the child periods in purple, all of them inside Period 1. An element that inherits its periods is not drawn: having no periods of its own, it has nothing to draw — which is why General training is missing from the chart above.

The parents of the person are not drawn either, because their lifespan is infinite.

Where each period is edited

Parent and child periods are not editable from this window: each is changed from the period window of its own element.

To change the period of Mario Rossi’s Forklift operator training, go to its detail form — Project / Office / Actions / Training / Courses / Forklift operator training / People / Mario Rossi — and click the period icon there.