Course · ← 0006 Choosing the Stack · capstone

Lesson 0007 · capstone · ~20 minutes

Model the System

Everything from lessons 0001–0006, collapsed into one schema you could defend in a design review. Do the sketch before you scroll — that is the whole exercise.

The brief

A defensible sketch

Not the only right answer — but every deviation from it should be a decision you can name.

-- everything below carries the temporal columns (lesson 0004)
--   begin_lifespan, end_lifespan          system time: when we believed it
--   begin_real_world, end_real_world      real-world time: when it was true
-- current state = WHERE end_lifespan IS NULL

party                        -- LA_Party
  id, type(natural|group|state), name, id_document, ...

party_member                 -- LA_PartyMember: who is in a group party
  group_party_id, party_id, share

spatial_unit                 -- LA_SpatialUnit
  id, label, geom(geometry, national grid CRS),
  capture_method(imagery|gnss|survey|sketch),   -- FFP: lesson 0002
  accuracy_class,
  boundary_type(general|fixed),
  predecessor_ids[]                              -- mutation lineage: lesson 0004

ba_unit                      -- LA_BAUnit: the seam (lesson 0001)
  id, label, type

ba_unit_spatial_unit         -- one BAUnit may bind several parcels
  ba_unit_id, spatial_unit_id

rrr                          -- LA_RRR: right | restriction | responsibility
  id, ba_unit_id, party_id, kind, type, share, status

source                       -- LA_AdministrativeSource / LA_SpatialSource
  id, kind(deed|court_order|survey_plan|photo|affidavit|testimony),
  document_ref, captured_at, submitted_by

rrr_source, spatial_unit_source     -- evidence links, many-to-many

-- systematic campaign machinery (lesson 0003)
adjudication_area   id, name, declared_on, display_from, display_to, status
claim               id, area_id, spatial_unit_id, party_id, asserted_rrr,
                    status(claimed|displayed|objected|adjudicated|registered|rejected)
objection           id, claim_id, objector_party_id, grounds, decided_on,
                    decision, decided_by

Why it is shaped that way

Rights never touch geometry. rrr points at ba_unit, never at spatial_unit. That one indirection is what lets a boundary be recorrected from better imagery without disturbing ownership, and lets one right cover three parcels — the payoff from lesson 0001 and 0004.

Claims are not rights. claim is a separate table with its own lifecycle, not a status flag on rrr. The authoritative register stays clean while 40,000 claims churn through display and objection — lesson 0003. Rows cross into rrr only on adjudication.

Geometry knows how it was made. capture_method, accuracy_class and boundary_type are what make incremental improvement possible and stop anyone treating an imagery trace as a survey — lesson 0002.

Evidence is a table, not an attachment. source is first-class and shared by both halves, because in a dispute the question is never just what does the register say but on what basis.

Group parties exist from day one. Customary holdings are the norm, not an edge case. Retrofitting party_member after launch means rewriting every ownership query you have.

Storage CRS: the national projected grid, so areas and distances are meaningful. Reproject at the service edge for web clients — lesson 0005.

Score your own sketch

• Rights attach to an administrative unit, not directly to a parcelIf ownership hangs off the parcel row, every resurvey becomes a rights event.
• Nothing is updated in place; versions open and closeNo UPDATE on a right, no DELETE on a parcel. Ever.
• Two clocks: when it was true, and when you learned itThe March deed lodged in September must record both.
• Parcels have predecessors and successorsSubdivision closes one and opens two; the old identifier is never reissued.
• Geometry carries capture method and accuracyOtherwise you cannot tell which of two disagreeing observations should win.
• Restrictions and responsibilities are siblings of rightsA mortgage is not a special kind of ownership.
• Group and customary holdings need no schema changeThe FFP continuum of tenure, in table form.
• Evidence is a first-class entity on both halvesDeeds and survey plans, same treatment, different kinds.
• Pending claims cannot leak into the authoritative registerSeparate table, explicit crossing point at adjudication.
• Areas and blocks are queryable entities with deadlines"What is in display until 14 March" must be one cheap query.
• Objections record who, against what, on what grounds, decided howThis is evidence, not a support ticket.
• Geometry is stored in a projected national CRSDegrees give meaningless areas; Web Mercator is for display only.

Nine or more, unprompted, and you can hold your own in a design review on this material. Fewer than six and the gap is worth a lesson of its own — say which boxes you missed.

Drill — the whole course, mixed

Where to go next

You now have the domain layer the mission asked for. The natural continuations, in order of usefulness to a build:

1. Read SOLA's actual schemaCompare it to your sketch above. Every difference is either something it knows that you don't, or a decision you can defend.
2. Get the LADM Part 1 textThe class diagram in full, including the packages this course only gestured at — survey, valuation, spatial plan.
3. Find a real donor RFP for a land systemReverse-engineer its requirements against these seven lessons. That is where wisdom starts.
4. Take one question to FIG Commission 7 or Land PortalPractitioners who have run these projects will tell you which of your assumptions is naive. No lesson can do that.