Home > Articles > Software Development & Management > Agile

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

LEGACY ISSUES

There are two particular issues to take up with regard to your legacy systems: mainframes and relational databases.

Mainframes

Most mainframe teams have different vocabularies and have been trained with techniques that are different from their object-oriented colleagues. Prepare for communication difficulties between the two teams and expect them to work in different ways. Many mainframe developers are used to working in a one-pass manner: "Give me the requirements; I'll do high-level design, low-level design, code, and test." Experienced OO developers are used to increments and iterations, multipass, iterative development: "I'll tell you the requirements after we 117 show it to our users twice" (see Chapter 5).

Partition the architecture so that the two groups can work in their own ways. Either get the mainframe developers comfortable with iterative development or develop a synchronization process that gives them their requirements only after the driving design is relatively stable.

The allocation of function to different platforms and languages may cause some trouble. The workstation and mainframe designers are likely to differ on which platform they believe a certain job belongs. This is not an object-oriented problem per se, but it is one that is likely to show up on your OO project. Defining the boundary of the OO system will require negotiation between the lead developers. Either they will have to agree or you will have to use a third party to work out the solution.

Consider using an "object-centered" design for the mainframe services to the workstation. Organize the services around the kind of requests coming from the workstation. The same objects are going to generate the same requests over time. Interestingly, object-centered design has twice been suggested to me by lead mainframe designers, not OO designers.

Relational Databases

Relational databases are fundamentally different from object databases and OO code. Here is a colorful allegory to illustrate the difference:

You are parking your car in an object-oriented garage. You drive into the garage, get out, close the car door, and walk into your house. When you want to leave again, you walk into the garage, climb into the car, start it, and drive away. You are parking your car in a relational garage.

You drive into your garage, get out, take off the car doors, put them onto the stack of doors; take off the wheels, put them onto the stack of wheels; take off the bumpers; and so on. You walk into your house. When you want to leave, you walk into the garage, take the doors off the doors stack, take the bumpers off the bumpers stack, take the wheels off the wheels stack, put them all onto the car's frame, climb into the car, start it, and drive away.

Putting relational data together is called joining. Joins are time-consuming, exactly as the allegory indicates. Fitting an object-oriented design to a relational database calls for additional table joins, usually to capture inheritance and many-to-many relationships. Reducing the number of joins needed is part of the strenuous work of fitting an OO design to a relational database. This one activity requires a great deal of communication, patience, and time. However, it is an important activity since it involves both the people and the models from the programming and the database communities.

The two communities and their models differ in a second key respect. Philosophically, a row in a relational table has no special "identity" beyond the data it contains. Any row that contains the same data is considered "identical." Not so for objects. Philosophically, each object has its own identity, so even when two objects contain the same data, they remain different. Naively putting objects into a relational database results in a clash, probably in the form of a long, drawn-out philosophical argument between the object and database designers over whether to add an identity field to the relational table.

Project Setup C.D., Independent Consultant

If I were to going to make recommendations for a large client/server project, here are a few things I would focus on given my experiences. I'm sure you will recognize a lot of these.

  1. Find the right help. Don't be the guinea pig for a newly formed consulting group that has decided that "objects are hot," and that's where they want to be. If the consulting group you are considering can 't provide references, it means that this is either their first project or that their other projects are "unreferenceable." Don 't become their next unreferenceable project. If references are given, call them, or better yet visit them to see what kind of development environment and development process the consulting group left them with.

  2. Be able to identify a technical architect for the project and make sure there is a commitment for that person to be involved in the project on a daily basis. Don 't settle for a "two-to three-days per week " type of arrangement, and don 't settle for an architect who appears to be a "really bright person " but who has "poor communication skills." Hiring an architect who can 't communicate effectively the hows and whys of the technical infrastructure to both management and programmers is a recipe for disaster. Your project should not be the first project of its type for the architect. Again, demand references.

  3. Realize that Smalltalk "out of the box "is not an appropriate tool for building complex client/server applications. Focus on transforming the completely generic development language/environment of Smalltalk into a business-specific development language/environment. Make sure that management understands the importance of this goal and is willing to allow for it in the project schedule and budget. If possible, develop your business-specific development environment over the course of several small projects. Whatever you do, don't hand your application developers Smalltalk and a database wrapper and let them "have at it."

  4. Strive to develop and communicate standard approaches/solutions to common development scenarios. During the project, take checkpoints and surveys of the types of issues that application programmers are having to deal with on a daily basis. Make sure that the provided frameworks and standardized solutions address those problems effectively. If a framework doesn't appear to be solving the right problem or is getting in the way of the development process, cut your losses and purge it from the development environment as quickly as possible.

  5. Document frameworks and solutions in a handbook you might title "Project ABC Developer's Guide/Cookbook. "It should present an overview of business-object schema and behavior (when it becomes available) and technical architecture. Address the 15,20,30 most common application development scenarios/problems and their standardized solutions, with pointers to examples. The solution may involve a framework, or it might just be a standardized way of solving a given problem. Examples of common problems faced by clientside developers are: How to retrieve, change, and save persistent business objects; how to translate business rules into code; and how to surface the facets and services of business objects to the GUI.

  6. Perform design and code reviews to ensure that new solutions aren't being invented for the problems that have already been solved/documented and to identify deficiencies in existing frameworks or the need for new frameworks or standardized solutions. 7.Make sure that opportunities for reuse between projects are exploited. Interproject communication is essential. Make sure that there is one solution developed and used for a problem that is shared by multiple projects; for example, technical infrastructure (persistence, validation, window management) and possibly even business domain objects.

Case material contributed by a third party, used with permission.

If the relational database's purpose is to support the objects, it will have to have an identity column. Technically, this is simple: Just use the unique key that is automatically generated by the database management system. The situation will be harder to resolve if the database has been there for a long time and it is not practical to add an identity column.

A third, greater hazard to your project when using a relational database is what is called the "persistence black hole." Rather than buying an OO database or buying a commercial framework for interfacing to a relational database, your team decides they can do the whole thing quickly and inexpensively by themselves. They say, "We'll just store the objects as rows. Easy enough."

A short while later, they find they have to optimize joins. Soon after, they find they have to handle transactions and transaction rollback. Then, they face checkpointing data and optimizing data transfer. Finally, they realize they have not adequately handled the object identity issue, and must retrofit that into the system.

In the end, they find they have built a small OO database system. It cost at least $300,000 for their two work-years of effort—perhaps triple that, if they were good enough to complete it at all. This little project-within-your-project swallowed your best programming talent for perhaps a quarter of your project's timeline. You would have been better off buying an object-oriented database to begin with.

If you do decide to use a relational database, search extensively for a company that has already built the persistence subsystem, then buy it. It will cost you much less, and will free up your best programmers to do your project work.

Beware of the "persistence black hole."
  • + 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