A patent application submitted by Paul Allen's Interval Research in 1998 envisioned groups of authenticated users sharing "lightweight messages" through a central server, using distributed client devices. This diagram from the patent shows those messages on a pen-based screen.

Microsoft co-founder Paul Allen's lawsuit last week against Apple, Google, AOL, Facebook and other online giants involves a total of four patents.

But as evidence of the wide-ranging ideas coming out of Allen's Interval Research in the 1990s, his representatives point out that the lab amassed some 300 patents in less than a decade of existence.

So what other types of technologies are we talking about here? A search of the U.S. Patent & Trademark Office database reveals a smorgasbord of patents tracing their roots to Interval Research -- including esoteric stuff such as memory cell arrays, wavelet-based data compression, a deferred scanline conversion architecture and, of course, the obligatory hierarchical memory architecture for a programmable integrated circuit having an interconnect structure connected in a tree configuration.

But then there's this: Method and apparatus for sending and receiving lightweight messages. And also this: Method and apparatus for sending presence messages.

Twitter and Foursquare, anyone?

To be clear, the patent filings don't read like precise blueprints for those two popular social networking services, and any formal comparison would require a careful review by a patent expert. One scenario cited in the "lightweight messages" patent, for example, involves scribbling messages on a shared virtual whiteboard.

But to the casual reader, the concepts outlined in each patent conjure up Twitter and Foursquare in the same vague way that the four patents at issue in the lawsuit point generally to the approaches used by Google, Apple and everyone else. Setting aside the specific scenarios, the basics of the claims are similar to existing online services.

Paul Allen

For example, here's an excerpt from the messaging patent: "The present invention teaches methods and apparatus for social interaction allowing users to communicate at their leisure (asynchronously or "semi-synchronously") by providing simple, flexible access to a persistent, shared space. For example, an electronic communication system according to one embodiment provides a shared persistent data space to a plurality of clients."

That patent application was filed in October 1998, and the patent was issued to Interval Research in February 2002.

The presence patent, meanwhile, describes a system that includes "a transmitting device at a first physical location that is responsive to a command intentionally initiated by a first individual at the first physical location to develop a presence signal intended for a second individual at a second physical location. The intentional presence system further includes a receiving device located at the second physical location which is receptive to the presence signal and which is operative to generate an indication to the second individual of the first individual's presence with respect to the transmitting device."

That patent application was filed in October 1998 and issued as a patent in October 2005. It's currently assigned to Allen's Vulcan Patents LLC, according to the filing.

Twitter and Foursquare were not among the eleven companies named in Friday's suit related to the separate patents. And even if these other patents are similar to what they're doing, it doesn't look like they have anything to worry about, for now. David Postman, a spokesman for Allen, said the priority right now is the case that was filed last week, given its size and the time and attention it will require.