This package permits real time links thru external "gateways."
Their C-based conNExions API Library has permitted development of links to Perl and TCL to allow rapid development of outside applications that can query, update, and otherwise manipulate spreadsheets in real time.
In effect, the spreadsheet software becomes a "data server" that other applications can talk to. This is a really, really powerful notion that the PC-based products just don't support. It deals with the robustness problem in that "real" data can be stored (in as safe fashion as is required) in a separate database, and values updated into the spreadsheet as needed.
Explanation of the difference between XESS and NExS
There is some unfortunate confusion between XESS and NExS; they have some common roots, and commonality in names.
xess.com is X Engineering Software Systems Corporation, a company formed by professors who were involved in the development of early versions of the XESS spreadsheet. They later developed and market a spreadsheet product that they call NExS.
ais.com is Applied Information Systems, Inc. a 25 year old company which develops, markets, and supports the spreadsheet product that is called XESS and related commercial products.
Both provide the "data server" capabilities described above that I would suggest makes them a fair bit more powerful than any of the other competitors, free or commercial, for any platform. I do not personally have enough experience with them to resolve the question of which, of the two, may be superior.
One user reports that Xess has a troublesome license management system; that seems a not completely surprising result.
Wingz is a fairly venerable (that does not forcibly mean that it's decrepit) spreadsheet product, long available for the Macintosh platform, now available as shareware for Linux. Interestingly, this once was a product sold by Informix in the days before they defined their mission to be to be the premier seller of database software.
It's somewhat slow; it appears that the calculation subsystem does not run in a separate thread from the screen subsystem, which means that recalculating blocks other operations which may get annoying if you're working with a large spreadsheet.
Another X/Motif spreadsheet package; they also have a DTP package Xclamation and have plans for a word processor called XAllWrite.
There are also a number of packages that are not exclusively spreadsheets (or wordprocessors or database systems), but also contain a variety of these subsystems that are considered useful for preparation of documents in office settings.
The makers have released SmartWare 2000, which may be different from the somewhat older version that I have used...
An integrated Pseudo-RDBMS / Spreadsheet / Word Processor / Comm software package with its own development environment. Runs under Linux, with either text mode or X11, MS-DOS, Microsloth Windows, and possibly other platforms. Priced at $50 for the "Personal Linux Edition." I have paid my $50. Interestingly, like Wingz , SmartWare used to be an Informix product. It was once reviewed in Linux Journal
I should note that my interest in it has been primarily predicated in its handling of spreadsheets. The wordprocessor component seems to be really rather klunky.
I found it interesting that the LJ review skirted around the issue of how compatible/friendly the user interface is. The user interface could be described as being somewhat clumsy and/or incompatible with user expectations. I think that the package has been around for quite a while, and likely predates common acceptance of IBM's CUA. It certainly isn't compliant with CUA standards. It does not have a similar user interface to that of Lotus 123, which I would also consider to be a "familiar" interface, and thus "friendly" to those of us that have used 123 a lot. (To instead call the 123 interface "intuitive" would be typical, and incorrect.) It is also possible that Lotus-compatibility was specifically avoided in order to avoid legal entanglements during the days of User Interface Lawsuits between Lotus, Borland, and Paperback Software.
The user interface on SmartWare isn't horrible; once your fingers get used to it, it's not hard to use. I find that I much prefer to run SmartWare in console mode rather than under XWindows; under X, it is much more "mouse-friendly," unfortunately to the point of requiring that some things be done using a mouse that could (in console mode) be more easily done using the keyboard.
Not much worked on since about 2000, this supposedly has a credible MS Access 'clone.'
Company that produces a "free" "Office" product, including word processor, spreadsheet, presentation, email, that run in Java in a web browser across the Internet, with documents "accessible anywhere."