SIS are IS made up by framgments (i.e., parts of an application element). Each fragment can be shared with other actors, whom can change the fragments, adopt them, rate them and so on. The aim is to provide enterprises with agile IS.
Here you can find a doctoral thesis on the subject: http://hal.inria.fr/docs/00/87/68/66/PDF/32523_QUAST_2012_archivage.pdf
There is a minitrack on social information systems on HICSS http://hicss.hawaii.edu/tracks-53/digital-and-social-media/#social-information-systems-minitrack