What is GEMMA?
GEMMA (Gemeentelijke Model Architectuur, Municipal Model Architecture) is the reference architecture for all Dutch municipalities: a coherent set of architecture products that describes how municipal processes, information, applications and infrastructure relate to each other. GEMMA is the municipal elaboration of NORA, the Dutch Government Reference Architecture, and is maintained by the Knowledge Centre for Architecture of VNG Realisatie (the implementation arm of the Association of Netherlands Municipalities) together with municipalities, suppliers and chain partners. Municipalities use GEMMA as a shared compass while keeping the freedom to make implementation choices that suit their own situation.
GEMMA translates the general principles of NORA into municipal practice: concrete, actionable and reusable.
🎯 What do municipalities use GEMMA for?
The Netherlands has 342 municipalities (as of 1 January 2026) that largely carry out the same statutory tasks, from civil registration and local taxes to the Environment and Planning Act and the social domain. Without a common reference framework, every municipality would reinvent the wheel. GEMMA serves three target groups:
| Target group | What they use GEMMA for |
|---|---|
| Municipalities | Designing business processes and information provision, writing project start architectures, procuring and replacing applications |
| Suppliers | Building software that fits municipal reference components and standards |
| VNG | A framework when representing municipalities in government-wide programmes and chains |
The main objectives are:
- Coherence and structure - alignment between processes, applications and data, within and between municipalities
- Reuse of standards - better interoperability and less dependence on a single supplier
- Local realisation of national frameworks - alignment with legislation and with NORA
- Accelerating digitalisation - a shared language for municipalities, suppliers and chain partners
🧱 How is GEMMA structured?
GEMMA is not a single document but a wiki-based knowledge base, GEMMA Online, with models in ArchiMate (version 3.1). Exchange between architecture tools uses the ArchiMate Model Exchange File Format.
| Component | Contents |
|---|---|
| Base architecture | Architecture principles and vision, business architecture (business functions and reference processes), information architecture and technical architecture |
| Theme architectures | Elaborations for case-oriented working, Common Ground, data, working with APIs, event-driven working, and privacy and information security, among others |
| Reference components | Vendor-neutral application types (such as a case registration component) with their functions, forming the basis of the application architecture |
| Standards | The GEMMA standards list, API standards, StUF messaging standards, information models such as RGBZ (case data), and the connection to base registers such as the BRP (personal records) and BAG (addresses and buildings) and to national standards such as Digikoppeling |
| Glossary | Unambiguous definitions so municipalities and suppliers speak the same language |
| Software catalogue | An overview of which packages support which reference components and standards, plus the application landscapes of municipalities |
GEMMA is also the framework for the quality norms in GIBIT, the municipal procurement conditions for ICT. That way, architecture agreements end up directly in contracts.
🕰️ How did GEMMA originate and evolve?
GEMMA was set up by the i-teams of the EGEM programme (Electronic Municipality), hosted by ICTU. When EGEM ended on 1 January 2010, the Quality Institute for Dutch Municipalities (KING) took over the work; those tasks were later absorbed into VNG Realisatie. Because the architecture had grown too large for a book, the wiki form of GEMMA Online was developed together with ArchiXL.
| Period | Development |
|---|---|
| EGEM period (until 2010) | GEMMA emerges as the reference architecture for municipal information provision |
| KING period | Further development, standards such as StUF and RGBZ for case-oriented working |
| Nov/Dec 2017 | Common Ground information architecture principles drafted (published January 2018) |
| 14 November 2023 | Renewed Common Ground five-layer model, now modelled in ArchiMate; FSC replaces NLX as the connectivity standard and an intermediary role is added |
| February 2025 | Publication of best practices on GEMMA Online begins |
Whereas GEMMA originally supported mainly the internal information provision of an individual municipality, it now also targets collective, fundamental improvement of municipal information provision.
🔄 What is Common Ground and how does it relate to GEMMA?
Common Ground is the municipal movement to decouple data from applications: data stays at the source and is exposed through standardised APIs instead of being copied into every package. Its five-layer model is included in GEMMA as a theme architecture:
- Interaction - portals and apps for residents, businesses and staff
- Process - process design and case handling
- Integration - one standardised connectivity facility, based since 2023 on the FSC standard (Federated Service Connectivity) as the successor to NLX
- Services - APIs that provide data
- Data - data sources following a standard information model
This separation of data and applications is also relevant to OT: sensor data from public spaces can be exposed through the same API approach, without every system keeping its own copy.
🔗 How does GEMMA relate to other government architectures?
| Architecture | Target group | Relation to GEMMA |
|---|---|---|
| NORA | The entire Dutch government | Parent architecture; GEMMA is the municipal elaboration |
| WILMA | Water authorities | Sister architecture, overlaps with GEMMA on water and sewerage |
| PETRA | Provinces | Sister architecture, overlaps with GEMMA on environmental policy and mobility |
| MARIJ | Central government | Government-wide variant for ministries and executive agencies |
| TOGAF | Generic enterprise architecture framework | A method that can be used alongside GEMMA for the architecture process |
🔐 How does GEMMA support information security and privacy?
GEMMA has its own theme architecture for privacy and information security. It makes traceable how municipal processes and applications comply with the BIO (Baseline Information Security for Government), the mandatory framework for all tiers of Dutch government, and with the AVG (the Dutch name for the GDPR). For municipalities, ENSIA is also relevant: the annual accountability system for information security, while the VNG’s Information Security Service (IBD) supports municipalities operationally.
In architectural terms this means:
- Security by Design and Privacy by Design - requirements are addressed per reference component, not afterwards
- Logging and records of processing - captured in GEMMA projects on logging of processing activities
- Governance - clear accountability for components and data, linked to the municipality’s information security policy
🏙️ Where does GEMMA touch operational technology (OT)?
GEMMA focuses mainly on IT, but municipalities also manage a lot of OT. This is exactly where OT convergence is well under way:
| Municipal task | OT component | Point of attention |
|---|---|---|
| Sewerage | Sewage pumping stations and measurement points, often via telemetry or SCADA | Alignment with water authorities (WILMA) and the lessons from Water Sector OT Security |
| Traffic | Traffic control installations, movable bridges, parking guidance | Availability and safety come first; strict network segmentation |
| Public space | Street lighting, smart sensors via LoRaWAN or other IoT networks | Expose street data according to Common Ground principles |
| Enforcement | Number-plate recognition cameras for low-emission zones, parking sensors | Personal data from the street: AVG, purpose limitation and logging of processing |
| Municipal buildings | Building automation in offices, swimming pools and sports halls | Maintenance by third parties; restrict remote access |
Practical approach: giving OT a place in the GEMMA architecture
- Inventory OT assets per municipal task and record them as components in the OT architecture, alongside the GEMMA application landscape.
- Model the interfaces between OT and IT in ArchiMate, so it becomes visible which data flows from the street to which case or asset management system.
- Define zones and conduits in line with IEC 62443 and apply Zero Trust principles to remote access by suppliers.
- Expose data through APIs rather than direct database links, in line with the five-layer model.
- Anchor ownership in risk management and architecture governance, so OT does not stay out of sight of the CISO.
❓ Frequently asked questions
What does the abbreviation GEMMA stand for?
GEMMA stands for Gemeentelijke Model Architectuur, Dutch for Municipal Model Architecture. It is the reference architecture for Dutch municipalities and builds on the Dutch Government Reference Architecture (NORA).
Who maintains GEMMA?
GEMMA is developed and maintained by the Knowledge Centre for Architecture of VNG Realisatie, in cooperation with municipalities, suppliers and chain partners. The architecture is published on GEMMA Online, where anyone can consult the models and views.
Is GEMMA mandatory for municipalities?
GEMMA is not a law but a reference architecture, so municipalities are not legally required to follow it. In practice GEMMA takes effect through procurement conditions such as GIBIT, through standards and through the Software Catalogue, which is why most municipalities and suppliers work with it.
What is the GEMMA Software Catalogue?
The GEMMA Software Catalogue is a public overview of software packages for municipalities, linked to the GEMMA reference components and standards. Municipalities use the catalogue for replacement and investment decisions and to compare their application landscape with that of other municipalities.
Which language is GEMMA modelled in?
GEMMA is modelled in ArchiMate, the open architecture language of The Open Group. The renewed Common Ground five-layer model from November 2023 is also expressed in ArchiMate, so municipalities can reuse the models in their own architecture tools.
Is this the same GEMMA as in machine building?
No, in the French-speaking automation world GEMMA stands for Guide d’Étude des Modes de Marches et d’Arrêts, a graphical method for describing the operating and stop modes of a machine, often used with GRAFCET (SFC). That GEMMA has nothing to do with municipalities; you will find comparable state models in PackML and ISA-88.
📌 In summary
GEMMA provides municipalities with a practical and coherent framework for structuring digital service delivery and data exchange.
GEMMA is the municipal elaboration of NORA, maintained by VNG Realisatie and captured in ArchiMate. With its base architecture, theme architectures such as Common Ground, standards and the Software Catalogue, GEMMA gives municipalities and suppliers a single shared language. Where OT and IT meet in public spaces, from sewage pumping station to traffic light, it pays to model and secure those OT assets explicitly alongside the GEMMA landscape.