Applying the technology mentioned above, the mobile device now can be utilized to obtain all the information in the database management system though the appropriate designed program and e-MARE framework.
The other information sources which are applied in another protocol are just the same technology as the above approach. That is, in another aspect, although some information sources do not provide the HTTP protocol (such as Z39.50) and web service to serve the remote user, they always still connected on the network. Furthermore, many of them are connected to the Internet, and serve their client in some specific network port. By default, the commands of e-MARE for fetching the web documents are through the standard HTTP port, which is numbered 80. For those information sources do not provide the HTTP port, the built-in commands of e-MARE can be applied for information retrieval of mobile users.
In such case, to design or to install the specific information application into the Mobile Agent
Execution Server of e-MARE is a feasible alternative solution.
7.3 Remote displaying via e-MARE framework
To be a mobile information carrier, the most important defect is the size of screen. The limited size screen of mobile device can not show large enough information at once. The user often scrolls the screen while she is reading documents, especially for the document that is not designed for mobile devices. Fortunately, because the e-MARE framework can initialize the remote application by operational e-mail through mobile device, the user can expand the mobile device’s display ability by implementing remote displaying, printing, and remote FAX. Following will explain the detail implementation.
Remote displaying technology is a very easy but useful application for the limited size mobile device to expand its displaying ability. The basic idea and architecture is shown in Figure 7.8. As shown in Figure 7.8, from the viewpoint of the user, she may compose an operational e-mail, which is combined with the displaying commands in the subject of that e-mail. Those commands will control the contents of Public Display Point (PDP) through the e-MARE server. In general, the related information about the contents of PDP and the controller is stored in the blackboard server. The e-MARE server will access that server to
find the most suitable information for displaying at PDP. That is, the user may modify the information of the blackboard system by e-MARE’s commands, and the PDP will generate the web contents according to the contents of the data table of the blackboard system.
Figure 7.8: The basic architecture of remote displaying technology.
As the earlier explanation and from the viewpoint of the server, PDP is the client of service, and it is merely a web browser which is browsing a specified web page of the server web site. The web page of server web site is controlled by a manager program, and the program will adjust the contents of web page according to the specified data item in e-MARE blackboard system. Because the specified data items are controlled by mobile user via e-MARE, the user may indirectly control the PDP via her mobile device.
For example, in this section, we construct a dedicated web site for remote displaying application which is addressed at http://www.twvs.tnc.edu.tw/~remote. To activate a PDP by that URL address has to be encoded with the site number, siteno. The homepage of
http://www.twvs.tnc.edu.tw/~remote/index.php?siteno=1 is shown in Figure 7.9.
Figure 7.9: The main webpage of http://www.twvs.tnc.edu.tw/remote.
As shown in Figure 7.9, because this is our first time to access the PDP #1, there are some messages shown in the web page remaining us to construct this PDP by RDON(1) command through e-MARE. After the user’s activated this PDP by RDON(no), the homepage of this PDP will soon be changed as shown in Figure 7.10.
Figure 7.10: The screen snapshot after the system has received the command, &&RDON(1).
As shown in Figure 7.10, each web page of remote displaying has its own serial number which is called Site Number. In this example, its Site Number is 1. This number is specified by the PDP while the browser has been connected to
http://www.twvs.tnc.edu.tw/~remote. If the user wants to browse the contents of listed web
site, she may just issue the &&RDC(id,1,no) command to the service account of e-MARE, if the user wants to view all links of the specified URL, the &&RDL is instead of &&RDC.For instance, if the user wants to browse the web page of http://news.yam.com/general, the user has to issue the command, &&RDC(id,1,3), in this PDP. Conversely, if the user wants to browse all links of the web page of http://tw.stock.yahoo.com/s/kimo_listE04.html and further dig those links on that page more depth, the command, &&RDL(id,1,3) is much preferred than &&RDC(id,1,3).
Meanwhile, the remote site serial number is started at 1, and the 0 is the page browsing commands. The mean of these commands are shown in Table 7.1.
Table 7.1: The mean of &&RDC(id, 0, n) commands.
Commands Description
&&RDC(id,0,0); Return to the homepage of http://www.twvs.tnc.edu.tw/~remote.
&&RDC(id,0,1); Scroll the screen to the top of the webpage.
&&RDC(id,0,2); Scroll Page Up.
&&RDC(id,0,3); Scroll Page Down
&&RDC(id,0,4); Scroll up one line.
&&RDC(id,0,5); Scroll down one line.
Each PDP has a unique site number. If a computer want to be a PDP, the only thing has to do is just to connect the specified URL address with the unique site number, which is shown as follows:
http://www.twvs.tnc.edu.tw/~remote/index.php?siteno=1
Because the HTML document of the mentioned URL is passive and has not be applied any other active client web technology (such as Java Applet or ActiveX), the page has to refresh itself regularly for updating the user’s requests. In our implementation, the document will refresh itself every 60 seconds. Each time while the page is refreshing, the program of web server will checks the actSite table of the database in the blackboard server to see if the status is changed or not. Then, the appropriate user-defined HTML document will be generated for the specified number of remote displaying site.
To activate the remote displaying function for the mobile user through e-MARE, the user
has to initiate the command &&RDON(siteno). After managerAgent of e-MARE has received the operational e-mail with that command, it will look up the user’s information from the user profile database, and check the user’s accessing right. If the user has the right to access the remote site, and the specified remote site has not registered yet, that specified site will be assigned to the mobile user, and give a time quota for the user’ accessing process.
This value (the default value is 100) will be stored at the TimeToLive field of actSite table.
Each time while the web page is being refreshed, the value of TimeToLive will be subtracted to 1. If finally the value of TimeToLive be subtracted to zero, the user’s related information will be wiped out from the actSite table of blackboard system. However, if the user’s has been to alternate any information in actSite table, the value of TimeToLive will be restored into default value. It means the user will enforce to be disconnected if she has not accessing her information on the data table for 20 minutes.
To achieve the earlier functionalities, the manager of system will maintain a table, called actSite, in blackboard system’s database, which is shown in Table 7.2.
Table 7.2: The table structure of actSite.
no Siteno Status TimeToLive showLinks user Id
Integer Integer Integer Integer Integer String Integer As shown in Table 7.2, the field ‘no’ is the serial number of all site number, and the
‘siteno’ is for identifying these data fields is for what site. The field ‘status’ is for recording the current state of the site, and ‘TimeToLive’ is a time period to see if the access ability of user is still valid or not. The field ‘showLinks’ is the direction to the web page to redirect to the appropriate web link. Finally, the field ‘user’ is the user’s account, and the ‘id’ is random number for each access phase of the user.
After the user has submitted the command, &&RDON(1), to e-MARE via the operational e-mail, the web page of site number 1 will be changed as soon as possible. The returned e-mail is shown as follows:
It means that the identification number is 9469170, and this number is the token for the user to further access the web document. However, if the remote web site is being handled