Tekli ve çoklu sistemlerde elektronik posta uygulaması

Abstract

Bir dizi büro iletişimi için telefona tercih edilmesine yol açan (ve başlıcası arşivleme yeteneğine bağlı olarak bilgi değişimini eşzamanlılık zorunluluğundan kurtarmak olan) Elektronik Posta, gerek modern işletmelerin gerekse her araştırmacının gün geçtikçe gereksinim duyduğu bir araçtır. Elektronik Posta uygulamasının en basit şekli tekli sistemlerle çalışanıdır. Terminalleri yöneten bir yazılım, dosya yöneticisi ve E. Posta uygulaması bu tür sistemler için yeterli öğelerdir. Ancak uygulama çoklu sistemlere genişletilmek istendiğinde fazladan bir iletişim mantığına ve posta transfer mantığına gereksinim duyulur. Bir "Mainframe" üzerinde çalışıldığı için, yukarıda sayılan gereksinimler kısmen de olsa karşılanmıştır. Ancak uygulamanın Dağıtık (Distributed) bir uygulama örneği olması değişik problemleri de beraberinde getirir: Veri yapılarının düzenlenmesi, uzak sistemlere dağıtılması ve işlenmesi, Elektronik Posta uygulamasının dağıtık ortamlarda çalışması problemlerden birkaçıdır. Elektronik Posta uygulaması oluşturulurken şu anda mevcut ve saygıdeğer firmalarca piyasaya sürülen ürünler incelenmiş, uygulamada tüm bu firmalarca sağlanan E. Posta hizmetleri karşılanmaya çalışılmıştır. Dağıtık veri işleme için olasılıklar incelenmiş, çeşitli olasılıklardan uygulamanın yapısına en çok uyan Dağıtık Enstantane Veri Yapısı (Distiributed Snapshot Data Bases) bulunmuştur. Uygulama programının dağıtımı; birçok makina üzerinde bir uygulamanın tekrar edilmesi şeklinde oluşturulmuştur. Bir başka deyişle aralarında eş bir ilişki olan bilgisayarlar arasında uygulama yatay ayrıştırılmıştır. Verinin iki sistem arasındaki transferi, dosya (file) transferi şeklinde oluşur. Mevcut sistemdeki dosya transfer hizmetinden yararlanılmasının yanında uygulamanın gerektirdiği kimi protokoller de geliştirilmiştir.

By any name, a confluence of computers, communication technologies, and demographics iş, transforming the way any enterprise conducts itself and carries out its organizational mandate. And it's happening fast. A business that ignores it will fall hopelessly to the rear in the global race for the competitive edge. At the heart of the transformation is information. No longer a byproduct - no longer, in many cases, even a cost center - the generation and movement of information has been made profitable by those who have taken up the technological challenge posed by the myriad machines that have automated so much of our lives. There are two dimensions to computer-communications software that a business needs to be concerned with: The application software that is provided for a community of terminals and computers; and the underlying interconnection software that allows these terminals and computers to work together in a cooperative fashion. The mere existence of a large population of computers and terminals creates a demand for these devices to work together. For example, when most of the employees in an organization have access to a terminal or personeal computer, then one of the most effective means of communication within the organization is electronic mail. If one employee needs to communicate with another, a message sent by electronic mail can be far more effective than the hit-or-miss attempts to catch the target in his or her office in order to reach the person by telephone. A detailed electronic mail message can be left in the recipient's electronic mailbox," to be read and answered when the recipient returns to the office. Other applications, such as the exchange of documents, the use of a data base that is distributed among a number of computers, and the ability to access many different computers from a single terminal, can be provided with applications software that is geared for the new networked environment. The key to the success of these applications is that all of the terminals and computers in the community "speak the same language." This is the role of the underlying interconnection IX software. This software must assure that all of the devices transmit messages is such a way that they can be understood by the other computers and terminals in community. Systems that store and process text and numerical data for business applications are generally termed computer-based information systems(CBIS). Four major types are in common business use:. Transaction processing systems. Management information systems. Decision support systems. Office automation systems The fourth system listed, the office automation system (OAS), is quite different in nature and scope from the other systems. Transaction, processing, management information, and decision support system are all concerned with information that reflects the state of the business and provides a record of its acti vites. Much of this information is numerical. Text information is likely to be in the form of fields in records (for example, in a personnel record, text information includes name, address, birthplace, job category within company, department, date of last salary review, and so on). The office automation system is primarily concerned with communication of information in the form of documents, messages, and memos. Office automation supports the creation, storage, and transmittal of these items. As originally conceived in the early 1970s, office automation was intended to automate the clerical and secretarial functions of an office. The centerpiece of such an approach is word processing, which dramatically increases productivity in document preparation, especially for documents that are revised. However, it was found that an office automation system could supplant a substantial amount of the paper communication within an office and thus contribute to improved efficiency. The prime example of this is electronic mail, which allows users to directly exchange and acknowledge memos by computer. This facility is valuable not only to clerical and support staff but can be used by professionals and all levels of management. Office Automation Systems Office automation is the one computer-based information system that cuts across all levels of manegement and staff and across all the activities of a corporation. The essence of such systems is the automation of tasks associated with documents, including memos and letters. Some examples of office automation capabilities are: . Creating and revising documents: This includes preparing correspondence, reports, proposals, contracts an manuscripts. This activity is usually called word processing and may include assambling a document from other documents that already exist.. Formatting documents: This capability has to do with how the test of a document is arranged on its pages. The user can specify and respecity the document format without altering the text. This can also be done with sophisticated word processing software. In addition, there are now a number of special form and document definition applications that can be used for special business forms, such as invoices, checks, and so on.. Printing documents: Often a number of users will have access to a shared printer, such as a letter-quality printer or laser printer. The system is responsible for queuing requests, printing docunents in turn, and notifying each user when the requested printing is completed.. Distributing documents: An electronic mail capability can be used to transmit memos and simple documents. More advanced document transfer capabilities are now emerging that allow documents with complex formats to be exchanged. Computer teleconferencing supports the exchange of messages and information among a community of users.. Filing and retrieving documents: Documents can be filed electronically in, and quickly retrieved from, a centrall library. The library may be distant from where the document originated or is to be used. The library facility may also include protection mechanisms that allow controlled access.. Processing documents: Users can request processing services for documents that are electronically stored either locally in their own office system or workstation or in a central library elsewhere in the office system network. For example, a user can create a document, then send it to a centrall library, and later request that it be formatted at that location and electronically distributed. Or a user can invoke library searches to identify documents meeting certain criteria (such as author name), then print or distibute those documents. Electronic mail, also know as a computer-based message system (CBMS), is a facility that allows users at terminals to compose and exchange messages. The messages need never exist on paper unless the user (sender or recipient) desires a paper copy of the message. Like voice mail, electronic mail solves many of the problems of communications between people by eliminating the necessity for both XI parties to an exchange to be available at the same time. In addition, electronic mail addresses the problem of the office paper explosion. Offices generate a tremendous amount of paperwork, most of it in the form of internal memos and reports: Over 80 percent of all business documents are textual and/or numeric (no graphlics) and originate and remain within the same organization. With an electronic mail facility, each user is registered and has a unique identifier, usually the person's last name and possibly the location as well. Associated with each user is an electronic mailbox. The electronic mail facility is an application program available to any user logged onto the system. A user may invoke the facility, prepare a message, and send it to any other user. The act of sending simply involves putting the message in the recipient's mailbox. The mailbox is maintained by the electronic mail facility and is in the nature of a file directory. One mailbox is associated with each user. Any incoming mail is simply stored as a file under that user's mailbox directory. The user may later go and fetch that file to read the message. The user reads messages by invoking the mail facility and reading rather than sending. In most systems, when a user logs on, he or she is informed if there is any new mail in that user's mailbox. An electronic mail facility performs these functions:. Creation: A- user ereates and edits a message, generally using a rudimentary editing cappability. Most systems also allow the user to create a message using the system editor or a word processor and then to incorparate the resulting file as the body of the message.. Sending: The user designates the recipient (or recipients) of the message, and the facility stores the message in the appropriate mailbox (es).. Reception: The intended recipient may invoke the electronic mail facility to access and read the delivered mail.. Acknowledgment: When mail is received, the sender may be automatically notified.. Storage: Both sender and recipient may choose to save the message in a file for more permanent storage.. Deletion: The user can delete messages once they are read.