Due to recent development of communication networks, obtaining data via networks such as the Internet (downloading) is widely performed. The data obtained via networks such as the Internet is usually stored in fixed memory such as a hard disk. The data stored in fixed memory, even after CPU (Central Processing Unit) and RAM (Random Access Memory) are initialized by restarting the terminal by turning the power of the terminal off once then turning it on again, or by resetting the terminal, can be accessed again by reading out the data from the fixed memory in which data is stored.
Also, when data is obtained via networks such as the Internet, the obtained data may even be stored in temporary memory such as RAM. An example of data in this manner is Java applet. Java applet is a program which is produced by utilizing Java (Java application). Java applet is obtained via networks such as the Internet and is stored in temporary memory of the terminal. Java applet obtained in the terminal is used via the browser for viewing Web pages written in HTML (Hyper Text Markup Language) and Java Virtual Machine. As described above, when the terminal is restarted, the temporary memory of RAM is initialized, and the data stored in the temporary memory is eliminated. When data obtained via networks such as the Internet is stored in temporary memory, it can not be used again unless the data is obtained again via networks such as the Internet after the terminal is restarted.
There are a number of Java applications, which, unlike Java applet, are stored in fixed memory after being obtained from networks such as the Internet, and do not need to be obtained again from networks such as the Internet even after the terminal is restarted. There are also Java applications which are stored in fixed memory of the terminal, and do not need to be obtained from a network. However, for the purpose of describing the present invention, “Java application” will hereinafter refer to a Java application which is obtained from a network since obtaining data from a network is the presupposition.
It is to be noted that whether the data obtained from networks such as the Internet is stored in fixed memory or in temporary memory, it is usually received from the network such as the Internet as a file. For instance, when a Java application consisting of a single file is obtained from a Web server by HTTP (Hyper Text Transfer Protocol), it takes place in one sequence, in other words, connecting to the Web server, requesting information, receiving the response and disconnecting from the Web server. In this case, as the user requests a Java application by operating the terminal, downloading starts immediately, and the connection between the Web server and the terminal is maintained until the download is complete. A message is displayed in the terminal indicating that a file is being downloaded.
In this method of obtaining data, the terminal user can not know property information such as the file size of the Java application before beginning to download it; hence, the terminal user can not predict the amount of the time required for downloading the Java application. There is a problem, therefore, that when a Java application consists of a plurality of files, use of the terminal may be restricted due to a longer than expected download time. This is extremely serious, especially for terminals such as cellular telephones in which a browser is installed which have a limited communication range or process capability. Necessary property information such as the file name of the Java application and the file size can, of course, be displayed on the Web page in the user's terminal, but there is the concern that some incorrect property information might be notified to the user due to erroneous descriptions or fraudulent intent.
To avoid the above mentioned problems, dividing a Java application into two files, ADF (Application Descriptor File) which contains property information and JAR (Java ARchive) which contains the entity of data, and receiving these in sequence at the terminal is suggested. JAR is a file type in which one or a plurality of files are organized into one. JAR is able to download a plurality of files in one operation, thereby saving the time required to download each file in a separate operation. However, when a file is divided into two files, ADF and JAR, the problem of ensuring security is not taken into account at all.