Our first attempts to use hypertext to go beyond anonymous ftp include the use of a table with the table entries linked to their corresponding data files. We also used pages with thumbnails of sky images which link the user to the data which the images map. Each of these methods of presentation has the benefit of providing some additional information beyond the name of the files which are available in the archive. The additional information assists in finding useful data. But in each case, the user is still presented with a large amount of information to process in making a selection.
Our current goal in data presentation is to develop methods of allowing the user to guide filtering mechanisms for selecting data. Two methods are being worked on. The first allows the selection of gamma ray bursts based on user selectable parameters in an html form. The second combines a form and an imagemap to allow the user to select objects from a map of the high energy gamma ray sky and specify which types of objects are of interest and the resolution of the selection on the sky map.
To ease anonymous ftp access, the data directories are divided up by instrument and then by data type and/or viewing period. So, for instance, if a guest investigator (GI) wanted to look at burst number 110 detected by the BATSE instrument, simply following the directory tree is all that is required to get to the data. First, "cd" to the BATSE directory, then to the bursts directory, and then to the BURST_00110 directory. Simple, obvious, and intuitive! But, only if you know exactly what you're looking for. Generally, this is not a good premise for we, the archive maintainers, to take.
Going a step further then, as the archive is cataloged in an Ingres database, we built a small vt100 Ingres forms interface to assist the GI in selecting information in the COSSC archive. Through the interface, a GI is able to specify a time period, an object, and even an instrument of interest. The query is then started and, soon, a list of file sets is returned. Although the file set names are somewhat informative, they're still rather reminiscent of the listing of filenames that is obtained from anonymous ftp. The GI is able to winnow the file list to some extent, but it is still, generally, very long and gives no indication of the parameters of the data stored in the files.
So, here again, the added value in data selection is rather limited. The limitations stem primarily from the lack of an interface powerful enough to display the parameters of the data efficiently and clearly for a GI to use in data selection.
Displaying thumbnails of sky images from the EGRET instrument was the first foray into data presentation on the web(EGRET Page). A GI is first shown a dynamically created list of viewing period ranges. Below is an example viewing period list:
Pointing 1.0 Pointing 2.0 Pointing 2.5 RA 5h52.28 RA 20h5.56 RA 5h51.32 Dec 17.14 Dec 36.58 Dec 12.47 L 190.92 L 73.28 L 194.86 B -4.74 B 2.56 B -7.29
Pointing 3.0 Pointing 4.0 Pointing 5.0 RA 12h46.16 RA 11h59.36 RA 18h1.56 Dec 2.62 Dec 41.52 Dec -30.96 L 299.76 L 156.18 L 0.00 B 65.46 B 72.08 B -4.00
Another area where we present GIs with all available data and tried to use the web to make some sense of that data is with the BATSE instrument's burst detections(BATSE Bursts Page). The BATSE bursts are listed in a table with position and date information. Here's a small portion of the table:
105 2B 910421 8367 33243.789 269.300 26.500 52.040 22.970 0.560 121.900 N N 107 2B 910423 8369 71684.750 196.700 -5.200 310.060 57.460 13.880 146.600 N N 108 2B 910424 8370 71006.602 171.900 -24.900 279.840 34.180 12.140 62.700 N N 109 2B 910425 8371 2265.740 92.400 -18.600 225.360 -17.370 0.960 84.300 N N 110 2B 910425B 8371 20253.320 346.900 22.600 93.640 -34.300 6.360 94.000 N N
For example, if a GI instead wanted all of the bursts detected by BATSE with a duration greater 50 seconds, then getting that information from the listing of burst numbers is quite possible. Each burst can be selected individually, then the for each burst the full report must be selected, and then the information must be extracted from each full report. Added value in that the information can be had online, but through a tedious and laborious process of information dredging.
Both of these cases, the EGRET sky thumbnails and the BATSE burst table, add some value to the data scanning process done by GIs. But, the GI still has to scan all of the data in order to ensure that all appropriate data has been found and to get some feel for the overall characteristics of the data. Additionally, the data which is available online is either limited, in the EGRET case, or presented in a format which can take some time to digest, in the BATSE full data report.
Getting the server computer to do the searching through the BATSE data is an obvious first step in adding value to the data presentations at the COSSC. Even if the server were just to search through the data in the basic table, as shown in the example, at least the GI would have fewer bursts to look through if some paring down of the data could be done based on date and burst position. But there is much more interesting data available describing bursts. Beyond the basic table from the example, there are several other tables which present various burst parameters. Certainly, each of these tables could be put online in the same fashion as the basic table to allow the GI scan the information and then select bursts for a review of the further hyperlinked information. But the GI is still scanning an enormous amount of data, and this time, the data is spread over several tables.
So we created an interface which has the user select parameters of interest, give bounds to those parameters, and then let the computer do the drudge work of scanning all the tables and presenting a combined table of the selected information(BATSE Burst Selector). The interface, seen below, presents the GI with a number of parameters to select as being active for a data search or not, and then allows the GI to select what sort of range will be imposed on those parameters.
Burst T50 Cmaxmin 64 222 57.024 5.523 1288 100.224 6.350 1533 85.376 5.663 1606 53.376 9.997 2156 92.032 17.156Return to Selection Page
For looking at data from the EGRET instrument, although a similar approach to that used for the BATSE instrument was possible given the multiple tables of EGRET data, because of the characteristics of the data and of the instrument we chose to use an imagemap built into an HTML form. The BATSE instrument on the Compton Observatory looks in all directions at once. On the other hand, the EGRET instrument is pointed at and only looks at a particular region of the sky at any one time. Additionally, the EGRET data tables, unlike the BATSE data tables which are separated by data parameter, are separated by object type. That is, quasars are in one table while pulsars are in another.
Our approach for EGRET is to present the GI with a map of the sky as seen by the EGRET instrument, showing the various objects that have been seen(Egret Skymap Selector). With the form beneath the graphic, a GI can specify what types of objects are of interest and what range of the sky to scan. The GI then clicks on the map at the center of the area of interest and a new page is returned with all of the data in that region. If a GI has specified no objects, then the nearest object is selected. Here's the initial page:
Table 2: Detected Pulsars
Source ID and Characteristics Pulsed Flux EGRET position ID Freq 1st Deriv 2nd Deriv 10^-6 cm^-2s^-1 l b error Ref Other Name B0833-45 11.20 -1.56E-11 5.65E-24 7.8+/-1.0 263.52 -2.78 0.04 degree 5,2 Vela VP = 0.7 Offset = 4.495249 degrees from observation center VP = 6.0 Offset = 29.890953 degrees from observation center VP = 8.0 Offset = 2.947890 degrees from observation center VP = 14.0 Offset = 21.602436 degrees from observation center B1055-52 5.07 -1.5E-13 - 0.24+/-0.04 286.1 6.4 0.30 degree 7 - VP = 0.7 Offset = 20.529377 degrees from observation center VP = 8.0 Offset = 26.078213 degrees from observation center VP = 12.0 Offset = 28.529850 degrees from observation center VP = 14.0 Offset = 7.215940 degrees from observation center VP = 32.0 Offset = 16.587111 degrees from observation center
Table 4a: Strongly Detected Unidentified Sources within 10 degrees of the galactic plane
Position Flux Source ID l b 10^-7 cm^-2s^-1 VP Notes Ref 3 - 14.4+/-2.4 6.0 10.4+/-1.9 8.0 7.1+/-1.1 14.0 <22.1 32.0 9.0+/-0.8 Allsky 4 - 8.8+/-1.9 8.0 5.5+/-1.0 14.0 <11.1 32.0 5.8+/-0.7 Allsky GRO J1110-60 290.99 -0.23 51 <14.9 0.7 - - <7.1 8.0 5.4+/-1.1 14.0 <12.0 32.0 4.8+/-0.7 Allsky
Using the web initially, we were able to present the data in the COSSC archive with some information which provided a little bit of guidance for making a selection from the data. Still, the presentation was tailored to present all, or at least a large chunk of the data to the a GI. This approach still presented a GI with a barrage of data to wade through to discover appropriate data.
Finally, by more fully utilizing the capabilities of HTML and the web, we were able to tailor our presentation of the data to the data. Thus, with data from the BATSE instrument, we are able to shape the data selection mechanism around the fact that BATSE data is primarily interesting for the characteristics of bursts rather than the pointing position or the of the instrument. EGRET data also benefits from the HTML capabilities with the presentation of an all sky map which lets a GI know which objects EGRET has seen and easily get to the data about that object. In each case, using features of the web and HTML, we were able to better tailor our information presentation to the needs of our user community.