Home > Articles > Programming > Windows Programming

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

This chapter is from the book

Discussion

In many systems, some use cases partly overlap; that is, a sub-sequence of actions is the same in several use cases. If this is a coincidence, and the sub-sequences are unrelated to each other and will be modified independently, no additional measures are needed. However, if it is required that these sub-sequences of actions must be the same, this requirement should be expressed in the model. This is done by modeling the common sub-sequence of actions, including its alternative flows, in a separate use case. When the performance of the sub-sequence is to be modified, only this use case will be updated.

It is important that the commonality encompasses a sequence of actions and not just a single action. Furthermore, if there is no explicit requirement stating that the sub-sequence must be the same in the overlapping use cases, there must be another significant reason for introducing the additional use case into the model (for example, to enable future reuse). If not, the complexity of the model will be increased without any defendable cause.

Obviously, the use-case model must comprise relationships of some kind between the use case modeling the common sub-sequence of actions and the use cases in which the sub-sequence is to appear. Which kind of relationship to use depends on the situation (see also Chapter 7, "Include: Reusing Existing Use Cases," Chapter 8, "Extend: Expanding Existing Use Cases," and Chapter 11, "Use-Case Generalization: Classification and Inheritance").

Sub-Sequence Independent of Context

If the sub-sequence must be independent of in which context it is used, an include relationship should be used, as in the Commonality: Reuse pattern. In this case, the base use cases will have include relationships to the use case modeling the common sub-sequence of actions. The description of the flow of the base use case will incorporate a reference to the included use case where the common sub-sequence is to be performed, but there will be no references in the other direction because the common sub-sequence is independent of its context (see Chapter 7). Reuse of the same sequence of actions in multiple use cases is a typical example of when to use the include relationship (see Figure 17.1).

Figure 17.1Figure 17.1 The PIN code is checked in multiple use cases.

In a library system, the borrower must always present the library card and a corresponding PIN code when registering a new loan, checking the existing loans, or extending an existing loan.

The sub-sequence checking whether the card is valid and whether the PIN code matches the card will be modeled in a separate use case to be reused in all the different loan-handling use cases (see Figure 17.1). When adding a new type of loan transaction to the library system, the new use case will have an include relationship to the existing Check Card and PIN Code use case. Hence, that sequence of actions will be reused when defining the new use case.

Note that the whole sub-sequence is to be performed at a single location in the base use case. It is not possible to split the sub-sequence in parts where one is to be performed at one location and the other at another location. If this is required, one include relationship must be defined for each sub-sequence part.

Additions to Existing Use Cases

When a new sub-sequence of actions is to be added to multiple already existing use cases, or when the same sub-sequence can be extracted from already existing use cases without breaking them or making them incomplete, an extend relationship is to be used. This is the Commonality: Addition pattern. In this case, the existing use cases will be independent of the common sub-sequence of actions, so their descriptions will not contain any references to the use case modeling the commonality. Hence, this use case can be added or removed without affecting the definition of the existing use cases (see Chapter 8).

Figure 17.2Figure 17.2 The check if someone has pre-registered to be the next borrower of a book is inserted into multiple use cases.

    Each time a book is returned to the library, the library system checks whether someone has pre-registered to be the next borrower of that book. If so, a notification is sent to that person and the book becomes unavailable for any other borrower within the next seven days.

    The same check is also performed when the librarian registers that the library has bought a new copy of a book.

    Because the Return Book use case and the Register New Copy use case are both complete in themselves, we can model this check in a separate use case, called Check Reservation Queue, that will have extend relationships to the other two use cases (see Figure 17.2).

Although all the behavior modeled by the extension use case will be added to the base use case, it is not required that all is added at the same location in the base use case. Instead, one part of the extension use case may be added to one location and another part be added to another location. However, if the parts have an internal order in the extension use case, they must be inserted in that order into the base use case (see Chapter 10, "More on Extend and Extension Points").

Similar Use Cases

Some systems include several use cases that perform similar tasks. One example is a warehouse management system where each type of order is carried out in a similar way. An automated production system is another example, where the different kinds of production directives are executed similarly but not identically. Because all the use cases modeling the performance of tasks are of the same kind, this commonality should be captured in the model. It is done by introducing a new use case that will model how a task is to be performed in general, including all the actions common to all kinds of tasks. The specific performances of the tasks are captured in separate use cases with generalization relationships to the new use case, as in the Commonality: Similarities pattern. The child use cases may specialize actions defined in the parent use case as well as add new ones (see Chapter 11).

Commonality Within a Single Use Case

In one use case, the same sub-sequence of actions may appear several times, typically in different alternative flows, but sometimes even in the same flow. In such cases, the common sub-sequence should not be extracted into a separate use case, because it only adds to the complexity of the model. Instead, the sub-sequence is described in a separate section in the description of the use case according to the Commonality: Internal Reuse pattern. When describing the flow of the use case, this section will be referenced from all the locations where the common sub-sequence is to be performed.

  • + 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