Home > Articles > Programming > Windows Programming

Agile MDA

  • Print
  • + Share This
Like this article? We recommend

Like this article? We recommend

Translating a Model

Executable UML defines groupings of data and behavior ("classes"), the behavior over time of instances ("state charts"), and precise computational behavior ("actions"). The reason for the quotation marks is that executable UML does not prescribe implementation. Rather, a "class" in executable UML represents a conceptual grouping of data and behavior that may be implemented as a class, or it may be implemented as a C struct and a set of associated functions, or as a VHDL1 entity. A "class" doesn't have to be implemented as a class. Consequently executable UML is a software-platform-independent language that can be translated into any target. For this reason, we also use the word "translatable" as well as "executable."

Models, Models, Models

There are at least three meanings of "model," and each one denotes diverse usages and connotes different processes. One denotation for the word "model" is a sketch. We sketch out the shape of a wing on the back of a beer mat, show a few lines indicating air flow, and write an equation or two describing how the two interact. The sketch is not complete, nor is it intended to be. The purpose of the sketch is to try out an idea. The sketch is neither maintained nor delivered.

Agile exponents are willing to sketch out their classes and use cases, sometimes called "stories," and perhaps even use UML to do it. There's no fight here: even the most extreme use sketches to outline their plans for the code.

A second denotation for the word is the model as blueprint. The physical model of the airplane in a wind tunnel is one example; more commonly, we think of a blueprint as a document describing key properties needed to build the real thing: the blueprint is the embodiment of a plan for construction.

The connotations of a model-as-blueprint cause conflict. The very idea of a "blueprint" evokes images of factories and manufacturing, together with uncreative drones. In an environment that is 80% construction and 20% design, like manufacturing, it makes sense to view the blueprint as the plan that is predictive of the construction work to be done. "Heavyweight" processes have encouraged the idea of model as blueprint; the manufacturing analogy is drawn repeatedly in the Software Engineering Institute's Capability Maturity Model (CMM), for example. But we know software is a creative new-economy thing, not at all like old-fashioned manufacturing. To the contrary, software is known for its creative aspects, entailing more like 80% design and 20% construction. In this case, developers need to be adaptive rather than predictive in their relationship to any model, effectively ruling out the use of models as blueprints.

The third denotation for the word is the model as an executable.2 The model of the airplane can be transformed into the real, physical airplane. The transformation requires other inputs, in this case the metal plates, bolts, and screws that make up the body, yet the model is complete in every detail in the one aspect of the problem related to the shape-that-flies. When we build an executable UML model, we have described the behavior of our system just as surely as we had when we wrote a program in Java.

Under this interpretation of "model" as an executable, a program in a high-level language such as Java is a model too. The Java program can be transformed into the real thing (byte code). The builder of the model, the programmer in this case, need not know how a Java compiler works, nor what the compiler does to make a program run. Of course, the byte code produced by the compiler is itself a model that can be replaced by ones and zeroes, one layer of abstraction removed, and those ones and zeroes in turn define the desired behavior of the underlying hardware, yet one more layer of abstraction away.

Many of the principles of Extreme Programming (XP) and the Agile Alliance involve process and customer relationships and their management, not code. As such, the agile process principles for the construction of code apply just as well for the construction of executable models. For those XP principles that do specifically mention "code" or "software," executable UML is code.

Executable UML allows developers to model the underlying semantics of a subject matter without having to worry about the number of the processors, data-structure organization, the number of threads, and so forth. In other words, just as programming languages conferred independence from the hardware platform, executable UML confers independence from the software platform, which makes executable UML models portable across multiple development environments.

At system construction time, the executable UML compiler maps conceptual objects to threads and processors. The compiler's job is to maintain the desired sequencing specified in the application models, but it may to choose to distribute objects, further order their behaviors sequentially, even duplicate them redundantly, or split them apart, so long as the defined behavior is preserved.

A program in C++ is complete and executable, but that doesn't do us much good until it has been transformed into some language that can be directly interpreted. We therefore run the program through a series of transformations that preserve the semantic content of the program (otherwise there's an error in the compiler) but express it in a language more oriented to implementation.

The same happens when we build a complete executable model. When we transform a model, tools populate the metamodel for the modeling language at hand. To carry our language example above to extremes, we could use the text of a C++ program to populate the instances of a model of C++ with classes Class, ProtectedMember, StaticMemberFunction and so on. As a result of the next transformation, we would have a model of C, in which instances of StaticMemberFunction and ProtectedMember would both be cast as ordinary functions, although with different signatures.

Such transformations may be continued indefinitely until the final, lowest, most grungy metamodel of them all. The classes in an (assembly-language) metamodel could be Instruction, Registers, MemoryLocation, and so on. The instances in this metamodel contain all the information of all the "higher level" models, but at a low level of abstraction.

An executable UML model compiler weaves together several models, where each model specifies some aspect of a system at a high level of abstraction. The weaving produces a single model that is at a lower level of abstraction. The model compiler then compiles the single model, producing textual code such as C++, Java, assembly, and so forth, which is at a yet lower level of abstraction. A C++ or Java compiler, or an assembler, processes the textual code in turn. Ultimately, this process generates code that runs over some virtual machine, such as the Java VM, or that runs directly over the CPU.

  • + Share This
  • 🔖 Save To Your Account

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.

Overview


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.

Surveys

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.

Newsletters

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.

Security


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

Children


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

Marketing


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.

Choice/Opt-out


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.

Links


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