iMail - 一個 WAP 電子郵件系統

Abstract

近年來，輕薄型電子裝置 (thin clients)，例如個人數位助理、手機或是網路家電 (Internet Appliances, IA) 等，紛紛投入網際網路的懷抱。相較於一般個人電腦，輕薄型電子裝置的運算能力較低、顯示螢幕較小、記憶容量較少及使用者輸入介面較為不方便。因此，網路與使用者間的互動關係將有別於原以個人電腦為主的世界。網路端不再將資料原封不動地由一個裝置傳送到另一個裝置上，而是依不同裝置的限制，將資料做適當的改變，以便於與各種輕薄型電子裝置互動。目前網際網路的協定 (protocol) 大部份是為個人電腦而設計的。這樣的網路協定並不適用於以輕薄型電子裝置為主的新環境。針對這個新的網路環境，本論文以電子信件讀取系統為例，設計一套便於輕薄型電子裝置使用的系統，稱為iMail，並且以無線應用協定 (Wireless Application Protocol, WAP) 實作iMail系統。實作結果顯示，以輕薄型電子裝置為主的新式網路環境，因種種的限制，在系統設計上與原網路環境有顯著的不同。針對輕薄型電子裝置的限制，本論文提出四項功能便於電子信件的讀取：信件過濾、二階段擷取、回復建議以及新信通知。信件過濾表示iMail 系統會基於使用者所設定的過濾條件，僅僅將重要的信件送達到使用者的輕薄型電子裝置。二階段擷取是用於減少傳送不必要的資料。回復建議功能藉由使用者過去的回信行為，針對目前閱讀的信件，以選單的方式建議應該回復那些訊息並寄給那些人。這項功能可減少使用者在輕薄型電子裝置上輸入文字所耗費的時間。針對新信通知，本論文還提出了三個機制：經常性詢問(polling)、轉寄(forward)及中繼轉送(relay)。除此之外，藉由實作iMail 的經驗，本論文亦提出一些設計及實作WAP應用程式的方針。本論文更提出IMAP+，亦即將iMail的功能植入到IMAP(Ineternet Message Access Protocol)中的構想。

Thin clients such as Personal Data Assistant (PDA), cellular phone, and Internet appliances (IA) are joining the Internet community. The common characteristics among these thin devices are their limited computing power, display, memory, and input interface. The network and user interaction would be changed. Network cannot simply be a dump pipe simply delivering data from devices to devices. The data information provided should adapt the different limitations of various devices. Many Internet protocols design guideline are based on assumptions that end-point devices are PC computers, and the protocols do not fit in such new environment. We design a mail retrieving system named iMail to facilitate email access for thin clients. We use Wireless Application Protocol (WAP) as an implementation environment to demonstrate the system and user interface design constrains for thin clients. To support mail retrieving in a mobile environment, we implement a mail agent with several features: mail filtering, two-phase fetching, response recommendation, and notification mechanism. Based on the user’s filter options, mail filtering delivers only urgent mails to the thin clients. Two-phase fetching is used to reduce transmission overhead of message delivery. The response recommendation suggests response operation and messages for user. This feature helps user reduce text typing through the unhandy input interface of thin clients. We also propose three mail notification mechanisms for iMail. When a new mail arrives, the mail notification mechanism informs iMail users immediately. Through the descriptions of the iMail features, this paper provides design and implementation guidelines for WAP applications. Furthermore, we propose IMAP+ that integrates the features of iMail system into IMAP. With IMAP+, the user mail server can directly support a flexible and convenient interface for wireless thin clients. ABSTRACT iii Acknowledgement iv Contents v List of Tables vii List of Figures viii Chapter 1 Introduction Chapter 2 iMail Architecture 2.1 Personalization Engine 2.2 Receiving Engine 2.3 Interface Translation 2.4 Response Engine 2.5 User Operation Chapter 3 iMail Features 3.1 Mail Filtering 3.2 Action Parameters 3.3 Response Recommendation 3.4 Two-Phase Fetching Chapter 4 iMail Implementation 4.1 WAP User Interface for iMail 4.2 iMail and Mail Server Interaction 4.3 Other Implementation Issues 4.3.1 Handset Capabilities 4.3.2 WML Character Set Chapter 5 Mail Notification Mechanisms Chapter 6 IMAP+ 6.1 Mail Filtering 6.2 Action Parameters 6.3 Response Recommendation 6.4 Device Capability Transcoding 6.5 New Mail Notification 6.6 From IMAP to IMAP+ Chapter 7 Conclusion Reference Appendix