Home > Articles > Programming

This chapter is from the book

5. Small Objects

Problem

How can you increase the framework’s flexibility while restricting its complexity?

Context

The overall scope and functionality for the framework is clear. You’re now in the process of breaking the overall functionality down into smaller pieces, such as individual objects or functions that applications can use.

Forces

Maybe your framework offers an interface to the applications that use it. Maybe it offers abstract classes that the concrete applications have to implement. Either way, it provides a certain amount of functionality to the applications. This functionality is typically expressed by a set of objects or methods—or functions, depending on the underlying technology. This invites the question of how these artifacts should be designed.

There are essentially two opposite approaches you can take. You can choose either a larger number of less powerful objects or a smaller number of more powerful objects.

From the application programmer’s viewpoint, both a smaller number of objects and simpler objects are desirable, because both make the framework easier to understand. But because you have to offer a certain amount of functionality, you cannot reduce both the number of objects and the individual objects’ complexity. You have to choose one and sacrifice the other.

Which option should be preferred?

You have to keep in mind that different applications will probably use your framework in slightly different ways. Combinatorics tell us that a larger number of less complex objects can be combined in many more different ways than a small number of very powerful objects. This flexibility represents a clear advantage.

In addition, complex objects are generally difficult to understand and difficult to reuse. This is true especially for objects with huge interfaces and methods that require many parameters.

Solution

When breaking down functionality into individual objects, favor a larger number of less powerful objects over a smaller number of more powerful objects.

Applications can then combine several objects to obtain a behavior that is tailored to their specific needs. This policy offers several advantages:

  • The objects the framework offers will be better understood.
  • Smaller objects have a better chance of meeting the users’ needs, since they are less specific to a certain context.
  • A larger number of smaller, somewhat atomic, objects allows for more combinations, and hence for an increased configurability of the application.

The price you have to pay for this strategy is that you cannot minimize the number of objects, but as long as the objects are fairly easy to understand, this seems a reasonable price to pay.

Examples

The Data Access Layer Framework

The data access layer framework allows the loading of business objects into its cache where they can be processed. Typically, an application loads a policy object and changes it, thereby also changing the policy’s state, which can be active, under revision, or offered to customers.

What happens when a policy object, one that is already in the cache, is requested? Should it be updated? Should the version in the cache be used instead? Different applications had different requirements. Some applications even needed to define a priority among states; for instance, an active object should be replaced by an object under revision but not vice versa. The framework team refused to include such a logic into the framework’s function for loading objects. Instead, they implemented two smaller functions: one that tells applications whether a certain object is already available in the cache, and another that loads objects. Applications can combine these functions to implement their specific logic.

Another example: The data access layer keeps track of which objects have been changed. At the end of a session, applications can commit all or some of the changes to the database. The team decided not to implement a complex function that saved all changed objects, but again decided to offer two functions: one that listed all changed objects, and one that saved individual objects to the database. Applications can combine these functions to implement their strategies of which changes should be committed to the database as they see fit.

The Web Portal Framework

The Web portal framework allows the applications to define certain use cases that specify the order in which user requests are processed and mapped onto calls of the back-end systems. The framework team decided to let the use cases’ objects consist of smaller entities—so-called "user-steps"—that the application developers could aggregate to full-fledged use cases according to their specific needs.

This solution turned out quite successfully. The definition of use cases was easy to understand, and the flexibility of the use case definitions made the concept useful for many applications.

Discussion

A framework should display The Beauty of Simplicity (2). Less functionality is often better than more functionality. But at some point we know that a certain functionality is not debatable, but strictly necessary. This pattern deals with the question of how this functionality can be implemented in such a way that different applications can use it most easily.

The suggestion to have small objects is similar to Don Roberts’ and Ralph Johnson’s suggestion to build frameworks from Fine-Grained Objects [Johnson+ 1998] and Brian Foote’s and Joseph Yoder’s recommendation to design objects with a Low Surface-To-Volume Ratio [Foote+1998], that is, objects with small external interfaces.

The benefit of using small objects is also related to the observation that small modules are more likely to be reusable, because smaller modules make fewer assumptions about the architectural structure of the overall system [Garlan+1995]; hence the risk of an architectural mismatch between components is reduced.

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