M Coding & Open Sovereignty: Dev Guide

M coding refers to the MUMPS programming language, a compact, multi-user language originally designed for medical records, while open sovereignty in this context means maintaining control over your code and data by using open standards and avoiding vendor lock-in. This article explains what developers need to know about M’s unique characteristics, its role in legacy systems, and how to approach it with modern open-source principles.

Background: The M Language and Its Ecosystem

M, also known as MUMPS (Massachusetts General Hospital Utility Multi-Programming System), was created in 1966 by Neil Pappalardo and colleagues at Massachusetts General Hospital. It was designed for managing large, hierarchical databases in multi-user environments, which made it a natural fit for healthcare applications. Today, M is still used in electronic health records (EHR) systems like VistA (the Veterans Health Administration’s system) and in many commercial healthcare products. The language is standardized by ANSI (American National Standards Institute) and ISO, with the latest standard being M21 (ISO 9899:2021).

Open sovereignty for M developers means using open-source implementations, such as YottaDB or GT.M, and adhering to open standards to ensure data portability and interoperability. This is crucial because many M-based systems contain decades of patient data that must remain accessible and under the control of the owning organization, not a single vendor.

How M Coding Works: Key Features

M is a procedural language with a unique syntax that can be challenging for developers coming from C-like languages. Its core features include:

Hierarchical Data Structures: M uses global arrays (persistent, multi-dimensional arrays) that are stored on disk and can be accessed by multiple users simultaneously. These are not like SQL tables; they are tree-like structures with string subscripts.
Compact Syntax: Commands are often abbreviated (e.g., s for SET, w for WRITE), and there are no explicit variable declarations. This makes code dense and fast to write, but also harder to read.
Multi-User and Multi-Tasking: M is designed for concurrent access, with built-in locking mechanisms for data integrity.
Interpreted and Compiled: M code is typically interpreted at runtime, but some implementations offer compilation for performance.

Here is a simple example of M code that sets a global variable and writes it to the console:

s ^patient("123")="John Doe"
w ^patient("123")

This sets the global ^patient with subscript “123” to the string “John Doe”, then writes it out.

Why M Still Matters: The Legacy and Modern Use

Despite its age, M is not obsolete. It powers critical systems in healthcare, banking, and other sectors. For example, the U.S. Department of Veterans Affairs’ VistA system, which manages medical records for millions of veterans, is built on M. Many commercial EHR systems, like Epic and Cerner (now Oracle Health), have roots in M or still use it for some back-end functions. In addition, M is used in some financial applications for its fast, reliable transaction processing.

For developers, understanding M is valuable for maintaining and modernizing these systems. Many organizations are looking to integrate M with modern web services, APIs, and cloud platforms, which requires a new generation of developers who can bridge the gap.

Open Sovereignty: What It Means for M Developers

Open sovereignty in the M context is about ensuring that your code and data are not locked into a proprietary vendor. This is achieved by:

Using Open-Source Implementations: YottaDB and GT.M are open-source M implementations that run on Linux and other platforms. They are compatible with the ANSI standard and can be used freely.
Following Open Standards: The M standard itself is open, so code written to the standard should be portable across implementations.
Data Portability: Since M globals are stored in a well-documented format, it is possible to export data to other systems, such as relational databases, using tools like M to SQL converters.
Community and Licensing: Open-source M projects are often licensed under AGPL or similar licenses, which ensure that modifications remain open and that users have the freedom to inspect and modify the code.

For developers, this means you can build new features on top of M without worrying that the underlying platform will be discontinued or that your data will become inaccessible. It also means you can contribute back to the community, improving the ecosystem for everyone.

How to Choose an M Implementation

When selecting an M environment for a new project or to modernize an existing one, consider the following factors:

Operating System: Most open-source M implementations run on Linux, but some also support Windows or macOS. Ensure your infrastructure can support it.
Performance and Scalability: Look for benchmarks and case studies that show how the implementation handles large databases and high concurrency.
Community and Support: A vibrant community means better documentation, more libraries, and faster bug fixes. Check forums, mailing lists, and GitHub activity.
Licensing: Understand the license (e.g., AGPL, BSD) and whether it fits your organization’s compliance requirements.
Integration Capabilities: Does the implementation offer APIs for calling M routines from other languages (e.g., C, Python, Java)? This is crucial for building modern interfaces.

Common Problems and How to Avoid Them

Developers new to M often face these pitfalls:

Syntax Shock: The lack of braces and the use of abbreviations can be confusing. Take time to learn the standard commands and their abbreviations.
Global vs. Local Variables: Globals are persistent and shared, while locals are process-specific. Mixing them up can lead to data corruption or unexpected behavior.
Concurrency Issues: M’s multi-user capabilities require careful use of locks (LOCK command) to prevent race conditions. Always lock before modifying shared globals.
String vs. Numeric Data: M treats numbers and strings interchangeably in many contexts, which can lead to subtle bugs. Use explicit functions like + to convert to numeric.
Error Handling: M uses ZTRAP or TRY/CATCH (in newer standard) for error handling. Not using them can result in cryptic errors and data corruption.

Comparing M to Modern Languages

M is often compared to other languages used for data-intensive applications:

M vs. SQL: SQL is declarative and set-based, while M is procedural and tree-based. M is better for complex, hierarchical data and transactional logic, but SQL is more familiar and has richer reporting tools.
M vs. Python: Python is more versatile and has a huge ecosystem, but it lacks M’s built-in multi-user persistence. You can combine them by using M as a back-end database and Python for data analysis or web services.
M vs. NoSQL: M’s globals are similar to NoSQL document stores, but with more powerful indexing and transaction support. M is often faster for certain workloads, but NoSQL systems like MongoDB are more widely used and have better tooling.

For most new projects, a modern language is a better choice. M is best suited for extending and maintaining existing systems where the data model is already in M.

Cost and Licensing Considerations

The cost of using M varies widely:

Open-Source Implementations: YottaDB and GT.M are free to use, even for commercial purposes, under the AGPL license. This eliminates licensing fees, but you must comply with the license terms if you modify the source.
Commercial Implementations: Some vendors offer proprietary M implementations with support and additional features, but they come with licensing costs. These are often used in large enterprises that need guaranteed support.
Training and Hiring: M developers are rare, so hiring or training can be expensive. However, the language is simple enough that experienced developers can pick it up quickly.

For organizations looking to maintain long-term sovereignty, open-source M is the most cost-effective option, but it requires in-house expertise.

Safety and Data Integrity

When working with M, data integrity is paramount, especially in healthcare. Key practices include:

Use Transactions: M supports transactions with TSTART and TCOMMIT to ensure atomic updates. Always wrap multi-step updates in transactions.
Backup Globals: Regularly back up the database files. Many M implementations offer online backup tools.
Validate Input: M is vulnerable to injection attacks if you concatenate user input into commands. Use parameterized queries or escape input.
Test Thoroughly: M code can be hard to debug, so write unit tests and use version control.

Alternatives to M for New Projects

If you are starting a new project, consider alternatives that offer similar benefits without the legacy baggage:

Relational Databases with ACID Transactions: PostgreSQL or MySQL with a language like Python or Java.
NoSQL Databases: MongoDB for flexible schemas, or Cassandra for high write throughput.
NewSQL: CockroachDB or TiDB for distributed SQL with strong consistency.

However, if you need to integrate with existing M systems, learning M is unavoidable. It is a niche skill that can be a career advantage.

Frequently Asked Questions

Is M programming language still used?

Yes, M is still used extensively in healthcare, especially in the VA and many commercial EHR systems. It is also used in some financial and other high-availability applications. Its longevity is due to its robustness and the massive investment in existing M-based systems.

How hard is it to learn M?

M is relatively easy to learn for basic tasks because the syntax is simple, but mastering its advanced features like globals, concurrency, and error handling takes time. Developers with experience in procedural languages will find it familiar, but the lack of modern features like objects (in older standards) and the unusual syntax can be challenging.

What is the difference between M and MUMPS?

M and MUMPS are the same language. MUMPS is the original name, while M is the official name used in the ANSI standard since 1990. Many people still use the term MUMPS, but M is the preferred name in professional contexts.

Can I use M with modern web technologies?

Yes, you can. There are tools like the EWD.js framework that allow you to build web applications using M as the back-end. Additionally, you can expose M routines as RESTful APIs using C or Python wrappers, and then use any modern front-end framework like React or Angular.

What are the main risks of using open-source M?

The main risks are a smaller community compared to mainstream languages, limited documentation, and the need for in-house expertise. However, the open-source implementations are mature and used in production in many hospitals, so reliability is proven. You also need to ensure compliance with AGPL if you modify the source.

How do I migrate from M to a modern database?

Migration is complex because the data model is hierarchical. You need to map globals to relational tables or document collections. There are tools that can help, but it often requires custom scripting. It’s a significant project that should be planned carefully, with data validation and testing.

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