Restrict events, event sets and triggers to a single hazard process type

[duncandewhurst]

@matamadio @stufraser1 in the proposed 0.3 schema, the array-type Event.processes, Event_set.processes and Trigger.processes properties have been replaced by string .hazard_process properties, i.e. restricting events, event sets and triggers to a single hazard process type.

I can't see this change discussed anywhere in the issues. Please could you clarify the reason for the change?

For reference, the decision to make the properties arrays was originally taken in #91 based on input from @stufraser1 in #91 (comment):

(...) yes one hazard type can include >1 process type eg flood can include pluvial and fluvial data

There's no technical problem with the change to strings, but it wouldn't be possible to model the scenario described above under the proposed schema.

[matamadio]

The reasoning behind the choice:

In the majority of cases, an events_set is made of individual events (e.g. RP scenarios) sharing the same attributes.
It is time consuming and ultimately unnecessary for explaining the dataset to specify child properties if they are all the same as the parent set; that should be optional for those cases when events in a set cover different processes.

• If all events in the event set use the same hazard type and process, then user can specify those at event set level only.
• If events have different process, do not specify hazard process at event set level; specify a different process (1) for each event.

Aligned to this logic, hazard type and calculation method are not required attributes anymore for a individual event - becomes so only if those are not specified at the events_set level.
That restrics events and triggers to one process, but does not restrict an events_set as each event can specify a different process.

Example:

Before change:

            "hazard": {
                "event_sets": [
                    {
                        "id": "FL_RPs",
                        "analysis_type": "probabilistic",
                        "frequency_distribution": "generalized_extreme_value",
                        "calculation_method": "simulated",
                        "occurrence_range": "Return period 2 to 1,000 years",
                        "hazards": [
                            {
                                "id": "FLD",
                                "type": "flood",
                                "processes": [
                                    "fluvial_flood"
                                ],
                                "intensity_measure": "fl_wd:m"
                            }
                        ],
                        "events": [
                            {
                                "id": "2",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 2
                                    }
                                }
                            },
                            {
                                "id": "5",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 5
                                    }
                                }
                            },
                            {
                                "id": "10",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 10
                                    }
                                }
                            },
                            {
                                "id": "25",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 25
                                    }
                                }
                            },
                            {
                                "id": "50",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 50
                                    }
                                }
                            },
                            {
                                "id": "100",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 100
                                    }
                                }
                            },
                            {
                                "id": "200",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 200
                                    }
                                }
                            },
                            {
                                "id": "500",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 500
                                    }
                                }
                            },
                            {
                                "id": "1000",
                                "calculation_method": "simulated",
                                "hazard": {
                                    "id": "FLD",
                                    "type": "flood",
                                    "processes": [
                                        "fluvial_flood"
                                    ],
                                    "intensity_measure": "fl_wd:m"
                                },
                                "occurrence": {
                                    "probabilistic": {
                                        "return_period": 1000
                                    }
                                }
                            }
                        ]
                    },

After change:

      "hazard": {
        "event_sets": [
          {
            "id": "FL_RPs",
            "analysis_type": "probabilistic",
            "frequency_distribution": "generalized_extreme_value",
            "calculation_method": "simulated",
            "occurrence_range": "Return period 2 to 1,000 years",
            "hazards": [
              {
                "id": "FL",
                "type": "flood",
                "hazard_process": "fluvial_flood",
                "intensity_measure": "Wd:M"
              }
            ],
            "events": [
              {
                "id": "RP2",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 2
                  }
                }
              },
              {
                "id": "RP5",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 5
                  }
                }
              },
              {
                "id": "RP10",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 10
                  }
                }
              },
              {
                "id": "RP25",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 25
                  }
                }
              },
              {
                "id": "RP50",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 50
                  }
                }
              },
              {
                "id": "RP100",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 100
                  }
                }
              },
              {
                "id": "RP200",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 200
                  }
                }
              },
              {
                "id": "RP500",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 500
                  }
                }
              },
              {
                "id": "RP1000",
                "occurrence": {
                  "probabilistic": {
                    "return_period": 1000
                  }
                }
              }
            ]

[duncandewhurst]

Thanks, @matamadio. That all makes sense from a data modelling point of view.

I had perhaps misunderstood the previous discussions to mean that a single event with a single related hazard type could have more than one related hazard process. That is certainly a question about the domain, so more than happy to defer to you on it!

[duncandewhurst]

Moving to changes needed since the modelling is agreed.