Software-Defined Defense & Interoperability: Enabling Modular, Secure & Agile Systems

Software-Defined Defense (SDD) is moving from concept to practice across Europe. German aerospace and defense engineers face the same challenges as their peers worldwide: deliver capability faster, keep systems certifiable, and avoid vendor lock-in. Yet tool silos slow down work. Data sits in different repositories. Models and code evolve on separate paths. Interoperability is no longer a “nice to have”; it is a requirement for mission readiness. 

This article outlines what SDD means. It also explains why interoperability is a central element of this approach, why it matters for the Bundeswehr context, and how to build a practical engineering backbone that supports modularity, reuse, and compliance, without throwing away your current toolchain. 

TABLE OF CONTENTS

1) What is Software-Defined Defense (SDD)?

2) Why SDD? 

3) SDD’s key foundations

4) The Benefits of SDD

5) Engineering the Foundations of Interoperability in SDD

6) Challenges in Implementing Software-Defined Defense

Final Thoughts

FAQ

1) What is Software-Defined Defense (SDD)?

Software-Defined Defense (SDD) describes a shift in defense systems architecture where functionality is primarily delivered and upgraded through software rather than hardware. It enables rapid and modular upgrades, deployment of new capabilities, cross-platform compatibility, and lifecycle agility.  

As software becomes more modular, hardware can be employed with greater flexibility, serving as a stable platform for diverse capabilities. This adaptability enables defense systems to be reconfigured for mission-specific needs without altering the underlying architecture. 

In practice, it means: 

• Hardware becomes a stable, well-defined execution platform, decoupled from specific software functions, so it can remain unchanged while the software evolves.
• Hardware can also be configured in a more flexible way, supporting new capabilities as modular software components are deployed. 
• Software components are modular, deployable, and updatable in short cycles. 
• Data is portable and accessible across tools, domains, and security enclaves. 
• Integration patterns are standards-based to reduce bespoke effort and vendor lock-in 
  

2) Why SDD?  

Geopolitical pressure and digital sovereignty make rapid capability development crucial for the Bundeswehr, the armed forces of the Federal Republic of Germany. Data volumes are rising, and computing capacity expands locally, on deployed platforms, and in secure clouds. At the same time, AI-assisted functions need fast integration and trustworthy data. And traditional platform cycles remain relevant, but speed now comes from software increments. 

In this environment, modular architectures and reusable components become the engine of SDD. Teams can deploy software updates in the field more rapidly, provided they comply with governance and certification requirements. They integrate analytics without breaking certification evidence, and avoid lock-in by standardizing interfaces rather than standardizing a single tool. 

 SDD as an answer to “Zeitenwende” 

Germany’s post‑2022 policy shift emphasizes readiness, agility, and digitally enabled forces. Software-Defined Defense provides a practical technical path. It supports faster fielding through modular software, enables joint and multinational interoperability, and reduces the long-term costs of maintaining and upgrading capabilities. The goal is not to discard legacy systems but to evolve them with a software-first approach. 

3) SDD’s key foundations

Three principles define the foundations of SDD.

1. Separation of software from hardware: the search for modularity and flexibility  

This principle allows defense systems to upgrade capabilities independently of physical platforms. For example, avionics software or mission-specific modules can be updated without redesigning hardware subsystems. It supports flexibility, lifecycle extension, and lower integration cost. 

A clear separation of software from hardware implies: 

• Platform layer: Provides the computing environment, handling processors, input/output operations, timing control, and core security mechanisms. 
• Service layer: Coordinates shared functions such as communication protocols, data handling, identity management, and logging functions. 
• Application layer: Implements mission-specific functions, analytics, and human-machine interface (HMI) logic. 

This architectural separation reduces the scope of impact during upgrades. Changes can be isolated to specific layers, which lowers re-certification effort and narrows the system’s attack surface. 

2. Separation of data from applications: real-time decision-making, data portability 

Separation of data applications means treating data as its own independent layer, decoupled from individual software systems, so it can be shared, reused, and processed consistently across multiple applications.  

By treating data this way, systems can enable real-time processing, data fusion, and portability across applications. This is critical for battlefield awareness, sensor integration, and autonomous system behavior. 

Data should be treated as a core asset of the organization. This requires adopting common schemas, OSLC links, and data contracts to ensure consistency. It also means managing provenance and lineage to maintain trust and traceability. Finally, governed access must be enabled so teams can collaborate across projects and classification boundaries. 

The concrete outcomes: 

• Faster analytics: Add new dashboards, reports, or AI models without having to rework every system that produces or uses the data. 
• Stronger traceability: Achieve model-based traceability from requirements to tests through links, not redundant copies. 
• Simpler data federation: Enable collaboration across services and nations with shared semantics.
   

3. User-centricity and automation: faster implementation cycles, retained human command 

Software-Defined Defense architectures enable user-centric workflows, leveraging automation for rapid deployment and updates. This helps shorten implementation cycles while preserving human control whenever it is requested.  

So, SDD does not remove humans from the loop. It makes human judgment more effective. Routine development and testing tasks are automated where safe, while operators and certifiers remain in control through clear and transparent evidence. 

In practice, this means:  

• Secure pipelines that follow policies suited for sensitive environments. 
• Automatic checks to spot issues in designs, requirements, and tests. 
• Role-based views that give engineers, testers, and decision-makers the right information for their responsibilities.

4) The Benefits of SDD 

Engineering Lifecycle Efficiency 

Modularity and shorter update cycles are reshaping the pace of engineering projects. Instead of re-engineering entire systems, teams can deliver targeted features through agile updates. Security and reliability fixes are no longer tied to major upgrades. They can be applied continuously, even during deployment. 

This approach also speeds up releases by replacing long, end-to-end testing cycles with smaller, incremental checks that steadily build confidence in system quality. With standardized modules, lifecycle management becomes simpler, making it easier to adopt solutions consistently across air, land, sea, and space systems. 

Reusability and Scalability 

Software-Defined Defense enhances both reuse and scalability by allowing components to be designed once and deployed across multiple platforms. New capabilities can be added incrementally, and decoupled components can be updated independently, lowering obsolescence risks.  

This modular approach also eases AI integration, enabling data-driven models to be added without disrupting certified systems cores, as long as interfaces and assurance measures remain clear. 

Cross-System Integration and Mission Compatibility 

Interoperability lies at the core of SDD, accelerating integration and strengthening mission outcomes. By aligning data exchange across sensors, command systems, and logistics, SDD supports seamless cross-domain operations.  

Standards-based interfaces ensure multinational readiness and enable coalition efforts. With stable interfaces and strong traceability, commercial technologies can be adopted faster. Changes then become manageable rather than brittle, preserving control over architecture and data. 

Economic and Strategic Advantages 

Software-Defined Defense delivers both economic benefits and strategic flexibility. Modular upgrades and automated migration lower integration and lifecycle support costs, while standard interfaces reduce reliance on single vendors.  

Faster development cycles shorten the path from prototype to deployment. This modular, open approach supports broader SDD economic goals. It enables cost reduction, new business models, and fair intellectual property sharing across the ecosystem. 

Security and Compliance 

Security in SDD must be embedded from the outset. Applying Zero-Trust principles ensures every request is authenticated and networks are segmented for resilience. Supply chain transparency is strengthened through SBOMs (Software Bills of Materials), provenance tracking, and vulnerability management.  

For classified environments, strict domain separation and strong encryption protect sensitive data. Continuous compliance is achieved by automating evidence generation to meet evolving standards and regulatory guidance. 

5) Engineering the Foundations of Interoperability in SDD 

In SDD, interoperability is not a single product or feature. It is a disciplined set of practices that links tools, models, and people across domains. It is essential because SDD depends on software and data as the primary drivers of capability, which requires consistent semantics, traceability, and data exchange across heterogeneous toolchains and organizational boundaries.  

Achieving this level of interoperability requires foundations that link information, preserve trust in evolving systems, and define clear rules for integration across domains. Without robust interoperability, modular upgrades, certification reuse, and coalition-level collaboration cannot be achieved, limiting SDD to isolated prototypes instead of scalable defense capabilities. 

Traceability, Migration, Reuse, and Collaboration 

➡️ Traceability – In SDD, interoperability relies on robust traceability, ensuring requirements, architectures, safety analyses, and tests remain linked across domains, tools, and versions. Standards like OSLC (Open Services for Lifecycle Collaboration) preserve semantics, automate coverage and impact analysis, and maintain lineage during migration.  

➡️ Migration – Legacy models must also be transformed into future-ready formats, with structure, semantics, layout, and identifiers preserved to retain certification evidence. Automated migration lowers risk and enables staged transitions where legacy and new repositories coexist.  

➡️ Reuse – Modular architectures, model libraries, open interfaces, and certification reuse accelerate approvals and simplify adaptation, allowing defense programs to evolve efficiently without re-engineering entire systems. Effective reuse also depends on managing versions and variants consistently. These valuable capabilities are supported by advanced practices such as Global Configuration Management, which keep complex system evolutions coherent over time. 

➡️ Collaboration and reviews – Interoperability is not only about data and tools but also about the coordination between people behind them. For instance, reviews must cross tool and organizational boundaries, aligning engineers, certifiers, and partners while preserving traceability and regulatory evidence.  

Beyond organizational alignment, interoperability also depends on technical precision at component boundaries, where contracts help define how independently developed modules can work together without ambiguity. 

Contract-Based Design: Specifying Interfaces to Manage Complexity 

Contract-Based Design is a paradigm for developing complex systems in which each component is associated with a contract, a precise description of its expected behavior. A contract specifies the guarantees a component provides, given that its environment satisfies defined assumptions. This approach enables compositional reasoning, stepwise refinement, and principled reuse of independently designed components. 

For Software-Defined Defense, Contract-Based Design strengthens interoperability by ensuring that modular components can be integrated with confidence. Formal contracts reduce integration risk, preserve certification evidence, and provide a clear basis for collaboration across domains, making them a natural complement to SDD’s modular and traceable architectures. 

6) Challenges in Implementing Software-Defined Defense 

Implementing SDD is complex. It requires shifting from traditional defense practices to a modular, data-driven approach. Interoperability, flexibility, and security must be ensured across evolving ecosystems. 

Legacy Tools and Data Silos 

Many defense programs still rely on monolithic toolchains, where data is shuffled around through document exports and emails. This makes cross-platform traceability fragile and error-prone. Progress usually comes not from replacing everything at once but by: 

• Linking existing tools instead of starting from scratch. 
• Preserving data integrity during synchronization. 
• Piloting a small scope (one capability or interface) before scaling up.

Measuring outcomes such as fewer defects, faster reviews, and less rework helps demonstrate real value. 

Contracting Models 

Contracting models, more specifically, frameworks that define how governments and industry structure agreements, can also be a source of slow progression. Traditional contracts give control to a single prime contractor and penalize change, which runs counter to modularity and iteration.  

A shift in mindset is needed, focusing on: 

• Procuring interfaces and data, not just deliverables. 
• Requiring open, testable specifications. 
• Rewarding reuse through shared model libraries. 

These practices create incentives for collaboration rather than lock-in. 

Security  

Security must evolve with modular and open systems. As more partners, tools, and data streams connect, the attack surface grows, and even small weaknesses can ripple across entire programs. Distributed collaboration brings these risks to the forefront, making it essential to apply “Zero-Trust” principles, where every user and service is verified at each step.  

Progress comes from: 

• Maintaining clear inventories of components and tracking vulnerabilities in the supply chain. 
• Compartmentalizing classified content while allowing redacted views for wider collaboration. 
• Weaving security evidence directly into the digital thread so audits can run continuously, not just as one-time checks. 

7) SodiusWillert’s Role in Enabling SDD 

At the heart of SDD is interoperability: the ability for tools, teams, and disciplines to work together without losing information or context. This is where SodiusWillert contributes. Instead of replacing entire toolchains, our solutions provide interoperability layers that connect tools, share data, and maintain traceability across the lifecycle. 

With OSLC Connectors, teams can link requirements, tests, issues, and models across ALM and PLM platforms while keeping data in its system of record. 

➡️ Explore OSLC Connectors

SECollab builds on this by enabling cross-discipline reviews, with clear dashboards and traceable feedback. 

➡️ Explore SECollab

For complex migrations, the Publisher Suite and Model-to-Model Transformation for Rhapsody (M2M) transformations automate safe transfers of models, documents, and frameworks, preserving structure and relationships so nothing is lost, and certification deliverables remain consistent. 

➡️ Explore Publisher Suite

SodiusWillert also supports Software-Defined Defense through its long-standing expertise in IBM Engineering Lifecycle Management (ELM) tools. For instance, requirements management tools such as IBM DOORS Next and system modeling tools like IBM Rhapsody play a central role in establishing disciplined, model-based engineering practices.

IBM DOORS Next ensures end-to-end traceability and powerful requirements governance, a fundamental prerequisite for the modularity and certification mandated by Software-Defined Defense programs.

➡️ Explore IBM DOORS Next

IBM Rhapsody enables the design and validation of modular architectures capable of supporting the separation of software and hardware layers, as defined by SDD principles.

➡️ Explore IBM Rhapsody

The combination of both requirements management and model-based systems engineering tools provides the foundation for consistency across the lifecycle. Requirements are directly linked to their architectural and behavioral representations, ensuring traceability from intent to implementation.

SodiusWillert's new AI extension for IBM Rhapsody, AI Modeling Assistant for IBM Rhapsody, further enhances these capabilities by automating the most repetitive modeling tasks and assisting engineering teams in building consistent, traceable, high-quality system models.

SDD is an engineering approach that makes software and data the primary drivers of capability. Realizing this vision in the Bundeswehr context depends on a strong interoperability layer, which connects diverse tools, disciplines, and data sources into a coherent and traceable engineering environment. 

Traceability must be established across domains and tools. Legacy models need to be migrated with their structure, semantics, and layout preserved. Cross-domain reviews should capture feedback as evidence within the engineering process. Reusable modules, clear data contracts, and versioned interfaces form the foundation for scalable and sustainable development. These are practical steps among many others. They fit real programs and real constraints. They also build a foundation for faster, safer, and more economical capability growth. 

FAQ

What exactly does “interoperability” mean in the context of Software-Defined  Defense? 
Interoperability means systems, tools, and teams can work together without reformatting or duplicating data. In engineering terms, it means artifacts are linked across tools with preserved semantics, interfaces are clear and testable, and evidence can be reproduced for any baseline. It is the opposite of brittle point‑to‑point file transfers. 

How is Software‑Defined Defense different from traditional digitization efforts in the Bundeswehr? 
Traditional digitization often put documents and workflows online but remained project‑ or tool‑centric. SDD is architecture‑centric and module‑centric. It separates software from hardware, and data from applications. It standardizes interfaces so that capability can evolve incrementally across platforms and partners. 

How can we test or validate interoperability when tools and models come from different vendors? 
Define interface and link conformance tests. Use OSLC to validate link types and coverage. Run end‑to‑end scenarios where requirements, models, and tests across tools are exercised together. Verify that IDs, semantics, and layout survive transformations. Treat these tests as part of your CI pipeline.

 
Do I need to change my entire toolchain to adopt SDD principles? 
No. Start by linking existing tools and establishing traceability. Introduce automated checks. Migrate selectively where models or frameworks block reuse. Replace tools only when there is a clear benefit. The goal is to reduce friction, not to restart the program. 

Can SDD be applied to legacy weapon systems, or is it only for new projects? 
SDD applies to both. Legacy systems benefit from interface stabilization, model migration, and traceability improvements. You can wrap legacy functions with clearer contracts and reuse common services. New projects can adopt modular patterns from the start.