The JGOAL collection of computer programs facilitates the real-time display, via the Internet, of multiple streams of data from the space shuttle and its ground support equipment at Kennedy Space Center. JGOAL is also readily adaptable to other applications that involve the real-time display of real or simulated data from other sources. JGOAL is so named because it is written in the Java programming language and because the data to be displayed are first processed for distribution over the Internet by a program called "PCGOAL," which runs on a server computer that receives the data streams from a common data buffer.
JGOAL was developed to overcome a limitation of PCGOAL that previously limited the availability of the data displays to a narrow class of clients: PCGOAL packages the data in such a way as to be suitable only for display on predefined screens of client computers that run the MS-DOS operating system and that are dedicated to displaying the data. JGOAL makes it possible to display the data on almost any computer connected to the Internet.
JGOAL is written in Java to take advantage of the compatibility of Java with all major modern computer hardware and operating systems, and with popular commercially available Web-browser software. This feature reduces the time and cost of development of Internet-compatible application programs, while maintaining security and portability. Java, which is an object-oriented language, supports application-program-development constructs that enable smooth mapping from requirements to implementation; this feature shortens development time further and minimizes the effort needed for maintenance.
The major costs of implementing most client/server computing systems occur at client sites. However, this is not the case in the system based on JGOAL. Because many client computers are now equipped with Web-browser software, there is no need to configure display systems and train users of JGOAL; there are no additional client-side costs for software, configuration, maintenance, or training.
JGOAL (see figure) includes the following programs:
- The Display Translator is an application program that converts a display description (DSP) file used by PCGOAL into a Hypertext Markup Language (HTML) file and a graphical background image file. The HTML and image files are used in the placement of the data in question within a display generated by a commercial Web-browser program.
- The Display Applet program is designed to run on a client computer in a commercial Web-browser program. The Display Applet program sets up the graphical display of the JGOAL information, establishes a network connection to the Data Manager (server) application program described next, and processes the data from the network connection to the JGOAL display.
- The Data Manager application program runs on the server computer, where it receives connection requests from the Display Applet (client) program, requests data from the common data buffer (which is, essentially, another server that operates independently), and sends the requested data to the client computer.
At the time of reporting the information for this article, the development of an upgraded combination of JGOAL and PCGOAL called "JView" was under way. JView is intended to enable a user at a desktop computer running Web-browser software to connect to a data server computer, select a data stream, and activate plot-window displays. JView is expected, when fully developed, to support the entire Kennedy Space Center user community (estimated at 800 users).
The JView application program would comprise two main subsystems: one for the server and one for the clients. The JView server subsystem would be responsible for communicating with a variety of data sources, acting as an archive of information and executable computer code, delivering requested data to clients, and regulating access through user names and passwords. The JView client subsystem would comprise JView applets (Java programs that would run within Java-enabled web-browser programs). It may become necessary to make the client programs downloadable as Java application programs.
JView client programs would support users' requests to generate selected static background displays, plot desired data streams, and manage alarm, display, and plot options. Upon startup, a JView client program would establish a connection with a JView server and download the requested data stream along with initialization values and other pertinent auxiliary data. Once the client program was initialized and all current data were received, the client program would enter a "listen" mode, in which it would periodically receive data-change values from the server. The client could also request that the server computer gather historical data from another server computer. The client computer would periodically notify the server computer of its status and of any significant changes in its configuration.
This work was done by John M. Dockendorf, Charles H. Goodrich, Mark Long, and Steven R. Beltz formerly of I-NET, Inc.; Ryan Stansifer of Florida Institute of Technology; Kevin Gillett of Princeton University; and Will Riddle of Duke University for Kennedy Space Center.
If your company is interested in the JView technology or need additional information, please contact the nonexclusive license holder Netlander, Inc., Stephanie Beever, Vice President, Florida/NASA Business Incubation Center, 1311 N. Hwy US 1, Suite 129-N, Titusville, FL 32796. Telephone: (407)383-5275, fax: (407)383-5273. KSC-11949