VISTA - A VISualization Tool and Analyzer.Introduction: Data retrieval is accomplished using a two-tier client server architecture. The data resides on a server and the bulk of the application resides on the client. The server can serve data both locally and over the network. Data management is accomplished using the concept of data reference. A data reference is the reference to the location of the data set and its characteristics. For instance, a time series data is referred to by a server address, filename, pathname, time window and a time interval. Some data references do not refer to actual data but refer to the set of data references and the operations to be performed on them to construct the data set. This provides transparency to the user. For the user there is no difference between such virtual data sets and the actual data sets. Data references can be aggregated in to a Group (Figure 2). The default view on a database file is a Group. Furthermore, one or more Groups form a Session(Figure 1). A Session can be saved and loaded from a file once created. The initial Session is created by opening a connection to some server and directory. The directory of database files then becomes a Session and each file becomes a Group containing data references. Data Manipulation is done by creating virtual data references which contain the set of data references and the operations to be performed on them. The actual operations on the data are performed only when the data for the reference is requested. Math operation such as division, multiplication, addition and subtraction are available between data sets. Period average and moving average, and merging are data references which are some other examples of manipulations on data sets. Data Visualization is done via two dimensional plots (Figure 3). Examples of such plots are time series plots and scatter plots. Zooming in and out and paging while zooming are some of the tools that are currently available. Printing is available in gif and postscript format. User has complete control of the attributes of each element in the graph. For instance the user can change the text, font, size, color and background color of the title. Most of these attributes can be saved to a file and applied to subsequent plots. Data can also be displayed and manipulated in tabular format (Figure 4). A graphical user interface is used to display a group of data references. The GUI is a view onto the application and contains no information about the application other than the way the application desires to be displayed. This separation enables support of undo/redo commands and the recording of macros which can then be replayed on different sessions. Scripting is an efficient way of accomplishing repetitive tasks.
Scripting uses the same application as the GUI and could use some of the GUI components as
well. Future: The concept of client-server is new in our part of the modeling world. Many new concepts are being tried here for the first time. The client and server functionality is fairly stable now and most of the current work involves extending and maintaining the applications. A lot of work is now going into documenting the existing application and its capabilities. For this purpose online help is being added and enhanced for the applications. Implementation of security and access control levels as fine as individual data sets
and the ability to access data using a schematic interface are features being considered
for future versions. A first beta version of VISTA was released to the Modeling Section in April 1998. Since then VISTA has under gone many bug fixes and enhancements including the addition of a scripting language and a GUI to interact with the scripts. This has resulted in VISTA undergoing many beta versions. A final version will be released soon. Figure 1 Figure 3 |
