Classification of information retrieval models

As mentioned in the section 2.2, to retrieve the information from the Internet in mobile computing environment needs a doable and convenient method. It has to let the mobile user getting the satisfied information by his mobile device under acceptable operating environment.

To further explain the feasible e-mail based solution for mobile computing environment, we first illustrate the current major models for getting information from the Internet. We divide the current information retrieval model from the Internet by retrieving style into three categories as follows:

„ Web-based Information Retrieval Model, WIRM

Web-based Information Retrieval Model, which is shown in Figure 2.3, is a traditional model for the user to retrieve the documents on the Internet.

It always also means the On-line Information Gathering Style which has been explained in section 2.2. Generally, the user in this model always executes a full functioned Internet WWW browser or information retrieval application to fetch the information and to operate the databases in real time.

It always requires high computing power platform and always on-line networking connection. In many cases, the client machine should be a powerful desktop PC or notebook PC and to be able to run such complex and powerful applications. Also, the client application always provides the good-looking and fantastic user interface for the user to issue his query to the specified information source, and the user always stays in front of the PC during the whole retrieving process. Because the user always keeps

concerning the whole progress of information retrieval, the response time from the information sources should be very critical.

Figure 2.3: The model of Traditional Web-based Information Retrieval Service.

Although most information sources of the Internet provide some kind of good-looking user interface for the user to fetch their documents, there still are few Internet search engines (such as Google, http://www.google.com) provide the concise but straightforward user interface for mobile devices’

(such as cellular phones or PDA) WAP browser or simplified mini-browser.

However, although the user interface is simple, those information sources still need to equip some sort of WAP-HTML gateway technology. Thus, when the user browses Google's web pages via mobile device, Google will first transform the original HTML format into WAP format. The mobile user then may use built-in or plug-in WAP browser to browse the Google's web pages. The WAP–HTML gateway technology is partly solving the information retrieval issues of mobile devices, but due to the translation technology between WAP and HTML is not mature (especially for Chinese web pages), and it can't optimize the results in a very short time, moreover, the mobile phone's wireless networking is very expensive, this is not a good solution for mobile devices to retrieve the information from the Internet.

„ E-Paper Style Information Retrieval Model, EPSIRM

The E-Paper Style Information Retrieval Service, which is shown in Figure 2.4, is a more flexible method for a user to fetch information from the Internet. A user can subscribe some kinds of E-Paper on the E-Paper provider web site in advance by their subscription interface which is provided by those famous information sources. After the user has been

subscribed and verified, the E-Paper provider web site will actively send some e-mail with the content of E-Paper specified by the user in advance to the user's mailbox periodically. All the contents of E-Paper from the web site are actively sent into user's mailbox, the user is not required to take care of any other chores except subscription. Of course, in most cases, there is no any customization mechanism for the user to adjust the contents of those e-papers.

Figure 2.4: The model of E-Paper Style Information Retrieval Service.

As mentioned earlier, this method is not required an always on-line networking connection. In addition, lots of networked mobile devices can read the e-mail directly. Thus, it is a feasible solution for most information retriever of traditional client platform, but one of the defects of the method is that the types of contents of E-Paper are limited, and in most cases, it has no way to customize the content to fulfill the user's personal requirements.

Moreover, the web site always assumes the client's machine is desktop PC or notebook PC, so it lacks some acceptable technologies to adapt the contents into different applications and platforms. Again, the most important defeat of EPSIRS is lacking of interaction mechanism between the user and the information providers. In most current E-Paper providers, there is no way for a user to operate any specified E-paper, and to further customize the contents of those E-Papers. Consequently, EPSIRM is not suitable for a mobile user who wants to actively and comprehensively retrieve the information on the Internet.

„ E-Mail based Information Retrieval Model, EMIRM

Using e-mail as the tool of information retrieval is not a new idea.

There were lots of researches and products using the e-mail protocol as the front end for other services (includes WWW, FTP, NNTP, Gopher, etc.) on the Internet at the era of poor infrastructure of network. Today, the quality of Internet networking for desktop computing environment is fast and stable.

The role of e-mail for information retrieval and other Internet services is replaced by multimedia-enabled web browser. However, for a mobile user with limited resources mobile device, most of the mobile devices have not enough computing power to execute the complex multimedia-enabled web browser and information analyzing works. The primary basic problem about limitation of resources for information retrieval is rising again.

In such a case, the best solution is letting the mobile device be treated as the front end client for the whole information retrieval process, and letting a powerful server as the back end server to fetch and analyze the documents from the Internet. The role of mobile device can be treated as the front end of information retrieval and only to provide a unified operating interface for the user to program, operate, and launch his remote applications, programs, or even mobile agents, and then wait the results returned from the programs or agents in the back end server. Due to most of the mobile devices has not the ability to execute the powerful web browsing, information retrieving applications, and the information analyzing applications, the interactions between the front end and back end are all through the e-mail protocol.

That is, if the user wants to retrieve some information from the Internet, he may have to compose an operational e-mail (which is a mail in a proper format for operating the remote applications or information retrieval process) to specified the interested information, and send it to the specified e-mail server. Then, the e-mail server will launch the information retrieval process for the user, and prepare the results into an e-mail. Few minutes later, the results will be sent back to the user’s mailbox. The user may browse the retrieved results from the Internet by opening the e-mail client application again. The mechanism of EMIRM is depicted in the Figure 2.5.

Figure 2.5: E-mail based information retrieval model.

As Figure 2.5 shows, the user will not directly access the information from the information sources on the Internet. On the contrary, the user directly access to the e-mail server. The works for actually retrieving and analyzing the documents are all done by e-mail server. The major advantage of this model is the efforts of the mobile devices will be dramatically reduced. All the chores can be finished on the powerful and high speed desktop PC or workstation with broadband networking connection.

In summary, the listed three models are suitable for each different hardware and software environment respectively. For the high speed computing environment with broadband networking, the first one is the most popular information retrieval model, but if the user has no time to sit at the front of desktop computer, or the user wants to get regular news and stuffs from some information providers, the second model is the best candidate for him.

However, if the user is on the road and grasps some kind of resource-constraint mobile device in his hand, to fetch documents or information from the Internet in such mobile device, the third model is the only suitable solution.