The Tessera data contract
Tessera enforces a platform-level data contract that project-scoped tools structurally cannot match. It produces coded, comparable, current data at the point of capture, not after months of post-hoc harmonisation.
Three pillars, six surfaces
The contract is enforced at the platform layer rather than the project layer. At a glance it has three pillars; underneath them sit six surfaces.
Governed concepts
Concept, value, and validation governance.
- Every variable carries a stable definitionId and a stable linkId. Question text can be reworded, translated, or clinically revised without the variable identifier changing.
- Retired questions are deprecated, never deleted, so historical data using a retired question stays valid and queryable.
- Inputs are coded against standard terminologies (ICD-10, SNOMED, LOINC, trauma codes). Where an authority maintains the codes, Tessera integrates live with the authority’s API.
- Ranges, conditional logic, dependency rules, and required-field rules are enforced at the point of capture, not at export time. Bad data does not enter the platform.
Governed lineage
Provenance and audit.
- Every data point carries its source system, source organisation, capturing user, form version, and capture date. The chain of custody is complete and queryable.
- Tessera maintains full user audit and full modification audit. Nothing is overwritten silently, and every change is traceable.
Governed analysis
Time, location, and reproducibility.
- Observations are date-stamped at the point of capture, so point-in-time queries are the default rather than a special feature.
- Geographic, organisational, and site dimensions are structurally present and queryable.
- The outcome is reproducibility: the same query against the same point-in-time anchor returns the same result regardless of subsequent schema or value-list changes.
A worked example: value governance
The TMS team's BC Trauma registry codes injuries, procedures, and outcomes against the Trauma Quality Improvement Program (TQIP), pulled live from the TQIP API rather than imported as a static list at project setup. As TQIP coding updates, the registry's code definitions update in step, and analytical comparability across reporting periods is preserved.
This is the value-governance pillar of the data contract in practice: the same concept maps to the same identifier across every record, and the value vocabulary stays current with the authoritative source rather than drifting against it.
Same query, same point-in-time anchor, same result. Analysts get coded, comparable, current data at the point of capture. Schema and value lists can evolve underneath without breaking historical analysis.
Where schema authority lives: the project, or the platform.
Project-scoped registry tools centre the project as the unit of schema and value-list authority. Each project builds its own variable names, value lists, and validation rules. At health-authority or provincial scale this produces schema fragmentation: the same clinical concept (INR level, NYHA class, a post-operative complication) has a different variable name, a different value vocabulary, and a different missing-value convention in every project. Cross-programme analysis requires manual harmonisation downstream, every time.
Tessera centres the platform as the unit of authority. Concepts have stable definitionIds and linkIds; values come from platform-managed terminologies that can be sourced live from authoritative APIs; validation runs at capture against the platform's contract. The same concept maps to the same identifier across every programme and every site, so cross-programme analysis is possible by default rather than after months of harmonisation.
REDCap and similar project-scoped tools put schema and value-list authority in each project; Tessera puts it in the platform. At provincial scale, that is what keeps cross-programme analysis possible without months of harmonisation.
Analytics-ready data at provincial scale
See how the data contract underpins registry management, or talk to us about your programme.