Welcome!

Microsoft Cloud Authors: Andreas Grabner, Stackify Blog, Liz McMillan, David H Deans, Automic Blog

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

An Architect's Guide to DSLs

Adding domain-specific languages to applications

You are an architect on your company's new flagship application. The app encompasses several business and technical domains that are, in your opinion, well suited to domain-specific languages (DSL). In years past, you would have turned to XML as the solution for all your DSL needs. With or without schemas, you would specify configuration files and scripts in files foul with angle brackets. Thankfully, for the discerning .NET architect, DSL implementation options are now plentiful.

For each DSL you create, you need to identify the target user for that DSL. Is she a non-developer subject matter expert, a particular kind of developer, or an end user? This choice will drive the kinds of tools you make available to support the DSL. It will also influence choices such as whether your DSL is interpreted or when it is compiled.

Before selecting DSL implementation strategies or tools, you need to decide the application layer in which each DSL will live. Some are intended to support run-time configuration and initialization. Others may be part of well-defined and reasonably confined components. Still other DSLs might be used to script together your application at the macro scenario level. Even particular idiomatic coding styles are essentially DSLs. Martin Fowler calls these "internal DSLs." These choices influence other architectural decisions. We'll begin our examination of the implication of some of these decisions with a brief description of DSLs in general. Then we'll look at different techniques for including DSLs in a larger architecture.

DSLs have several advantages over general-purpose programming languages (GPLs). DSLs directly support high-level concepts from the business domain with program constructs (services, classes, interfaces, and libraries, whatever is appropriate to the target technology and the business requirement). The language takes responsibility for transforming, compiling, or interpreting those business concepts into a working system. When the business domain and technology expertise are encapsulated in a DSL, users of the language boost productivity while also improving quality.

It's useful to point out that the boundaries between GPLs and DSLs are fuzzy, if they exist at all. For example, C was originally created for the purpose of system programming. Perl was originally created for text processing (which is still its best domain). Java was an environment meant for set top boxes and then Web applications. Lisp was originally created for AI research. Now it's used in an operating system masquerading as a text editor. Even COBOL and Fortran are DSLs, although not Business DSLs (BDSLs). Many people say DSL when they mean BDSL, where business is used in the same sense as business logic. For purposes of this article, I would like to include business domain and non-business DSLs. In many IT shops, the non-business DSLs outnumber the BDSLs.

Whether business-specific or not, each DSL should provide the ability to say useful things over a well-defined domain. This implies the ability to describe a domain and the ability to specify the grammar and semantics of statements or expressions ranging over the selected domain. A BDSL should be created only where an organization has a clearly defined domain with well-understood semantics, and then it should mimic the normal forms of communication used when discussing the domain. From an architectural perspective, what we're really thinking about is providing points in an application architecture where domain concepts are expressed in more natural forms.

When it comes to including DSLs in an architecture, how you implement a DSL and where it fits in your architecture are closely related. There are many approaches to implementing DSLs, from literate (sometimes called intentional, although there are other meanings for intentional) programming to fully compiled custom languages. We'll start with the most prominent DSL creation tool in the .NET sphere and work down toward simple code-style implementations.

A typical enterprise component architecture like the one shown in Figure 1 presents many opportunities for serving domain expert users with DSLs. Any one of the components might include a DSL for configura-tion purposes or as part of its public interface. In addition, a DSL could be used to wire together or orchestrate interactions between multiple components in a single module or subsystem.

In September, Microsoft released another CTP of the Domain-Specific Language Tools (http://lab.msdn.microsoft.com/teamsystem/workshop/dsltools/default.aspx). The final release of the DSL Tools, planned to come on the heels of the Visual Studio 2005 RTM, will provide everything necessary to create visual domain language editors that can be used to generate code or for other DSL-related purposes. Microsoft provides tutorials for the current DSL Tools release. I won't rehash them here. The key to understanding the role Microsoft's DSL Tools play in architecture is that they give you the ability to create graphical editors for DSLs. The graphical notation maps to some other form, most commonly a textual representation. In this sense, the DSL Tools can be applied in the exact same way as textual DSLs.

One approach to including DSLs in an architecture is to use modular design to encapsulate DSLs in specific pieces of an application. A component or module might be configured by or execute logic provided by a DSL. Common examples of DSLs of this type are template engines, database access layers (using SQL as a language), and rules engines. In this approach, the DSL is part of the public API of the component. DSLs used in this fashion are often formally defined or documented textual languages. This is the approach commonly described for external DSLs. The architectural challenges are relatively simple in this case. Each DSL is implemented in a well-defined component.

The example in Figure 1 includes a business rules engine that interprets business rules defined in a visual or graphical DSL. The Data Adapter's interface gives dependent components the ability to provide SQL for specific operations not supported by the underlying mapping technology.

Finally, the Template Engine uses templates stored in the file system. The templates may be defined using XML, a graphical editor, or some other notation. The purpose for using DSLs in each of these components is to provide a more natural or efficient expression of logic in the domains - in this case business rules, data access, and templates - than is provided by a GPL like C# or VB.Net.

When providing documentation for a component that uses one or more DSLs, it is good practice to provide, along with standard interface documentation, a guide to the DSLs supported with several nontrivial examples. DSLs may provide a better way of communicating or capturing ideas in particular domains, but they can add to the surface area and complexity of components. It's important to weigh the benefits of creating and implementing a DSL against any additional learning curve that comes with it. Microsoft's DSL Tools will make language construction more accessible for application developers, but they won't eliminate the need to properly document DSLs.

There are other approaches to DSLs that involve using the internal capabilities of a language or platform to support a DSL-like experience for developers. UML provides one way to define an internal DSL. A domain model such as the one shown in Figure 2 describes a business domain in a formal notation. The domain class diagram captures part of one possible description of the business domain of libraries. For space reasons, it includes only those elements that are critical to the examples. The approach to the domain model class diagram in Figure 2 is based on color modeling (see the first entry in the References section). As with the other topics addressed in this article, there are several good choices when it comes to approaches to domain modeling (see second and third entries). As you will see from the references, the topic of domain modeling has been around for a long time. Microsoft's DSL Tools, Model Driven Architecture (MDA) solutions such as Borland's Together Architect 2006, and the emergence of what Martin Fowler has called "language workbenches" are generating new interest in domain modeling and DSLs (see the fourth entry).

More Stories By Dan Massey

Dan Massey is chief technical architect at Borland, where he works on Borland's Software Delivery Optimization (SDO) solutions. Prior to joining Borland, Dan was a TogetherSoft mentor and JEE architect and developer.

Comments (3) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
realworldsa.dotnetdevelopersjournal.com 01/02/06 12:45:16 AM EST

Trackback Added: VSTS 2005, DSL, and Software Architecture; Microsoft needs to get on the ball as to what Software Architecture is and what we need to be successful, so far VSTS 2005 is greatly lacking.

Tad Anderson 01/02/06 12:37:18 AM EST

This is the danger I see in DSL tools from MS...

I think every yahoo in the world who likes to re-invent the wheel will be putting out their own designers.
Full Read... http://realworldsa.dotnetdevelopersjournal.com/dsl.htm

Tad Anderson 12/20/05 07:08:14 PM EST

My thoughts on DSL:
http://realworldsa.blogspot.com/2005/12/vsts2005-dsl-and-software-archit...

@ThingsExpo Stories
The Internet giants are fully embracing AI. All the services they offer to their customers are aimed at drawing a map of the world with the data they get. The AIs from these companies are used to build disruptive approaches that cannot be used by established enterprises, which are threatened by these disruptions. However, most leaders underestimate the effect this will have on their businesses. In his session at 21st Cloud Expo, Rene Buest, Director Market Research & Technology Evangelism at Ara...
"When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
In this presentation, Striim CTO and founder Steve Wilkes will discuss practical strategies for counteracting fraud and cyberattacks by leveraging real-time streaming analytics. In his session at @ThingsExpo, Steve Wilkes, Founder and Chief Technology Officer at Striim, will provide a detailed look into leveraging streaming data management to correlate events in real time, and identify potential breaches across IoT and non-IoT systems throughout the enterprise. Strategies for processing massive ...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists looked at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deliver...
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...