Home > Articles > Software Development & Management > Architecture and Design

Introduction to Model Driven Architecture

There have been significant improvements in the ways in which we build software over the last fifty years, two of which are worthy of note in the attempt to make software an asset: we've raised the level of abstraction of the languages we use to express behavior, and we've sought to increase the level of reuse in system construction. MDA takes the ideas of raising the levels of abstraction and reuse up a notch. It also introduces a new idea that ties these ideas together into a greater whole: design-time interoperability. Want to learn the basics? Start right here.
This chapter is from the book

This chapter is from the book

There's no doubt about it: Software is expensive. The United States alone devotes at least $250 billion each year to application development of approximately 175,000 projects involving several million people. For all of this investment of time and money, though, software's customers continue to be disappointed, because over 30 percent of the projects will be canceled before they're completed, and more than half of the projects will cost nearly twice their original estimates.1

The demand for software also continues to rise. The developed economies rely to a large extent on software for telecommunications, inventory control, payroll, word processing and typesetting, and an ever-widening set of applications. Only a decade ago, the Internet was text-based, known only to a relatively few scientists connected using DARPAnet and email. Nowadays, it seems as if everyone has his or her own website. Certainly, it's become difficult to conduct even non-computer-related business without email.

There's no end in sight. A Star Trek world of tiny communications devices, voice-recognition software, vast searchable databases of human (for the moment, anyway) knowledge, sophisticated computer-controlled sensing devices, and intelligent display are now imaginable. (As software professionals, however, we know just how much ingenuity will be required to deliver these new technologies.)

Software practitioners, industrial experts, and academics have not been idle in the face of this need to improve productivity. There have been significant improvements in the ways in which we build software over the last fifty years, two of which are worthy of note in our attempts to make software an asset. First, we've raised the level of abstraction of the languages we use to express behavior; second, we've sought to increase the level of reuse in system construction.

These techniques have undoubtedly improved productivity, but as we bring more powerful tools to bear to solve more difficult problems, the size of each problem we're expected to tackle increases to the point at which we could, once again, barely solve it.

MDA takes the ideas of raising the levels of abstraction and reuse up a notch. It also introduces a new idea that ties these ideas together into a greater whole: design-time interoperability.

Raising the Level of Abstraction2

The history of software development is a history of raising the level of abstraction. Our industry used to build systems by soldering wires together to form hard-wired programs. Machine code let us store programs by manipulating switches to enter each instruction. Data was stored on drums whose rotation time had to be taken into account so that the head would be able to read the next instruction at exactly the right time. Later, assemblers took on the tedious task of generating sequences of ones and zeroes from a set of mnemonics designed for each hardware platform.

At some point, programming languages, such as FORTRAN, were born and "formula translation" became a reality. Standards for COBOL and C enabled portability among hardware platforms, and the profession developed techniques for structuring programs so that they were easier to write, understand, and maintain. We now have languages like Smalltalk, C++, Eiffel, and Java, each with the notion of object-orientation, an approach for structuring data and behavior together into classes and objects.

As we moved from one language to another, generally we increased the level of abstraction at which the developer operates, which required the developer to learn a new, higher-level language that could then be mapped into lower-level ones, from C++ to C to assembly code to machine code and the hardware. At first, each higher layer of abstraction was introduced only as a concept. The first assembly languages were no doubt invented without the benefit of an (automated) assembler to turn mnemonics into bits, and developers were grouping functions together with the data they encapsulated long before there was any automatic enforcement of the concept. Similarly, the concepts of structured programming were taught before there were structured programming languages in widespread industrial use (for instance, Pascal).

Over time, however, the new layers of abstraction became formalized, and tools such as assemblers, preprocessors, and compilers were constructed to support the concepts. This had the effect of hiding the details of the lower layers so that only a few experts (compiler writers, for example) needed to concern themselves with the details of how those layers work. In turn, this raises concerns about the loss of control induced by, for example, eliminating the GOTO statement or writing in a high-level language at a distance from the "real machine." Indeed, sometimes the next level of abstraction has been too big a reach for the profession as a whole, only of interest to academics and purists, and the concepts did not take a large enough mindshare to survive. (ALGOL-68 springs to mind. So does Eiffel, but it has too many living supporters to be a safe choice of example.)

As the profession has raised the level of abstraction at which developers work, we have developed tools to map from one layer to the next automatically. Developers now write in a high-level language that can be mapped to a lower-level language automatically, instead of writing in the lower-level language that can be mapped to assembly language, just as our predecessors wrote in assembly language and had that translated automatically into machine language.

Clearly, this forms a pattern: We formalize our knowledge of an application in as high a level a language as we can. Over time, we learn how to use this language and apply a set of conventions for its use. These conventions become formalized and a higher-level language is born that is mapped automatically into the lower-level language. In turn, this next-higher-level language is perceived as low level, and we develop a set of conventions for its use. These newer conventions are then formalized and mapped into the next level down, and so forth.

The next level of abstraction is the move, shown in Figure 1-1, to model-based development, in which we build software-platform-independent models.

01fig01.gifFigure 1-1. Raising the level of abstraction

Software-platform independence is analogous to hardware-platform independence. A hardware-platform-independent language, such as C or Java, enables the writing of a specification that can execute on a variety of hardware platforms with no change. Similarly, a software-platform-independent language enables the writing of a specification that can execute on a variety of software platforms, or software architecture designs, with no change. So, a software-platform-independent specification could be mapped to a multiprocessor/multitasking CORBA environment, or a client-server relational database environment, with no change to the model.

In general, the organization of the data and processing implied by a conceptual model may not be the same as the organization of the data and processing in implementation. If we consider two concepts, those of "customer" and "account," modeling them as classes using the UML suggests that the software solution should be expressed in terms of software classes named Customer and Account. However, there are many possible software designs that can meet these requirements, many of which are not even object-oriented. Between concept and implementation, an attribute may become a reference; a class may be divided into sets of object instances according to some sorting criteria; classes may be merged or split; statecharts may be flattened, merged, or separated; and so on. A modeling language that enables such mappings is software-platform independent.

Raising the level of abstraction changes the platform on which each layer of abstractions depends. Model-based development relies on the construction of models that are independent of their software platforms, which include the likes of CORBA, client-server relational database environments, and the very structure of the final code.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020