1197 
browser 
3.1 A typical User Session 
an experimental Ionia “ lion " 
server system for publishing 
oth in Local Area Networks 
server is compatible with the 
im. a distributed hypermedia 
iERN. In addition to the stan- i 
Net-Browser offers features , 
ervation data as: 
chartism suitable for file- 
ter with image icons 
ease the network operations 
is retrieved. 
te product boundaries on the 
ny Internet site by different 
its like CELLO 2 on MS-Win- 
tdows. Apple-Macintosh anti 
onnected to Internet is con- 
Uions of hosts are fully cen 
to an exponential growth the 
lications for Network Infor- 
VWW and WAIS. An exam- 
c is shown on the following 
IS 
WWW 
366 
0 
2.899 
39 
4.591 
512 
5.416 
3.W 
5.935 
8.116 
5.604 
17.298 
* Bytes (Source: NSFNET) 
ws to broadcast recently 
tion to the world-wide com- 
U the CERN, Geneva SwitzerUmi, 
system which uses HTML (Hyper 
i for its internal formats, and HTTP 
Institute. Cornell Law School, 
¡cations. Champaign, IL USA 
A browsing session begins with the connection of the user’s cli 
ent to the Net-Browser server. The service is identified by an 
URL 1 that defines the protocol and the host ad dress.The Net- 
Browser displays a the home page with description of the ser 
vice and with instructions for query formulation (see Home 
Page Figure). 
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The Query Map Interface 
Concerning the query formulation, the user is supported with 
• a hyperlink to a Query Syntax page which provides a 
detailed description of each keyword. 
• a hyperlink to a page of examples and predefined queries. 
• a world map where the user can point to the desired location 
A query can be typed into the appropriate text field in the Home 
page and forwarded by hitting return. The server can search ac 
cording to different criteria. A minimum set of keywords sup 
ported by the search engine includes: 
* the latitude and longitude of a point covered by the image. 
* a date range in which the image falls. 
* a quality parameter (e.g. cloud coverage, percentage of 
water, etc.). 
* mission identifier. 
Alternatively, the user can access, through a link in the same 
Home page, a fill-in form interface supported by HTML+ com 
patible clients (e.g. Version 2 of the NCSA X-Mosaic). The 
fonn embodies type-in fields, option menus, radio- buttons and 
push-buttons which provide an easy and intuitive way of for 
mulating the query, showing at the same time the values of de 
fault for keywords. A query request is sent by clicking on the 
appropriate push-button. The items retrieved for a query are 
L Universal Resource Locator 
packed in small groups to avoid long network delays in case of 
a large set of images. The groups are formed and sorted accord 
ing to dates. 
The Query Fill-in form Interface 
Each group can be viewed in three different modes: the List with 
comments mode gives essential Quick-Look data such as dates, 
cloud coverage, satellite, coordinates, etc.; 
The Mixed Mode Display