Home > Articles > Open Source > Python

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

This chapter is from the book

Component Interaction: Choose Your Model

Finally, you should consider how the various components of your web framework are going to interact. Some frameworks, such as Webware and Xitami, include facilities for interaction between their components. You can always use socket programming for such interactions, but this has two potential disadvantages. The first is simply the amount of programming required, and the second is the lack of generality.

If your components need to communicate with others, there are two systems in general use that are designed to facilitate such interactions, and another two newer ones that focus on the use of a combination of XML and HTTP. Because they are all complex, it is only possible to give the briefest of outline to close this chapter.

The Common Object Request Broker Architecture (CORBA)

CORBA is a heterogeneous system for locating and using services in a networked environment. It is an open standard maintained by the Object Management Group (OMG), whose web site (http://www.omg.org) prominently features CORBA. The site also describes UML, the Unified Modeling Language used to describe services, and CWM, the Common Warehouse MetaModel, which describes complex data structures for interchange between structured repositories. These last two topics are not considered here.

You describe a CORBA service interface in the OMG Interface Definition Language (IDL). This allows you to specify the data to be passed between objects in a platform-independent manner. Python CORBA interfaces can parse IDL to allow CORBA-mediated interactions between arbitrary system components using the features of Xerox PARC's ILU project, for which Python provides the reference implementation. For a full description see ftp://ftp.parc.xerox.com/pub/ilu/ilu.html. ILU is a free, CORBA-compliant, object request broker (ORB) that supplies distributed object connectivity to myriad platforms using a variety of programming languages.

The CORBA architecture is designed to allow clients and servers of particular services to locate each other on the Net and interact by means of what CORBA calls transactions. These are simply programmed interactions rather than the database transactions discussed in earlier chapters.

Microsoft's Distributed Common Object Model (DCOM)

Mark Hammond, Greg Stein, and others have interfaced Python to Microsoft's COM, Distributed COM, and ActiveX architectures. This means, among other things, that you can use Python in ASP or as a COM controller (for example, to automatically extract from or insert information into Excel, Access, or any other COM-aware application). Python can even be an Active Scripting host (which means you could embed JScript inside a Python application, if you had a strange sense of humor).

Python support for many Microsoft Foundation Classes (MFC), COM, DCOM, and Active Scripting is integrated into the ActivePython distribution available from http://www.activestate.com. You can also download the win32all extension package separately if you already have Python installed on your Windows computer.

The major disadvantage of DCOM when compared with CORBA is its restriction to Microsoft-supported environments. DCOM is not an open system because Microsoft controls the standards. This might not matter if you work exclusively with Windows anyway. There has been some work to bridge the CORBA and DCOM worlds using IIOP, the Internet Inter-ORB Protocol, but this has not so far led to massive integration between the Microsoft world and everything else.

DCOM has also proved to be difficult to scale to larger systems without explicit use of MTS. Although this is an acceptable overhead for large-scale projects, it appears to require disproportionate effort for small- and medium-sized developments. A good description of DCOM technology, along with many examples of how Python can be integrated into the DCOM environment, is available in Programming Python on Win32 (Mark Hammond and Andy Robinson, O'Reilly).

XML-Based Interactions

Various communication schemes are current that use XML to encode remote requests and responses between system components, the two best known being XML-RPC and SOAP. SOAP is of interest to web developers because it uses HTTP as the request/response transmission protocol and so is available wherever web services can operate. Microsoft has built its BizTalk services around SOAP, carving out an early market share in distributed services. The XML-RPC camp promotes technologies that allow a similar style of interactions, with all data interchanged using XML.

It will be interesting to see whether BizTalk is operated as a closed framework: if third parties do not run BizTalk servers, then even Microsoft may not be able to provide a large enough infrastructure to win out over an open systems protocol. SOAP itself is receiving broad support across the industry, by companies as large as IBM, so its future seems assured independently of BizTalk.

One of the "features" used to promote SOAP and similar techniques is that it uses HTTP, which corporate firewalls already accommodate. What this really means, however, is that any server that can be accessed for web services can also be accessed for remote procedure calls after it becomes SOAP-capable. This would seem to be a somewhat specious argument in favor of SOAP because opening firewalls to other RPC protocols like IIOP would only involve substantially the same risks. Whether the managers of corporate firewalls will want to allow SOAP traffic to continue to pass unhindered after they appreciate its implications remains to be seen.

  • + 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