Format  Representation Examples
Fuzzy undefined/marginal/complete, don't know/untrustworthy/marginal/full PGP's direc trust
Fuzzy very trustworthy/trustworthy/untrustworthy/very untrustworthy Ruth/Xu/Bhargava/Regnier's RT0
General Lattice Moreton/Twigg
General Binary (yes, no) + possible supplementary information Trust management (Blaze/Feigenbaum's PolicyMaker and KeyNote)
Integer Virtual currency {0..infinity} Trustos in ubiquitous computing (http://www.trustos.com); maybe the Nuglets in mobile ad-hoc networks (http://www.lst.inf.ethz.ch/research/publications/publications/COM_MAG_2001/COM_MAG_2001.pdf)
Integer {-infinity..infinity} Slashdot.org's Karma; Ebay's feedback rating
Integer 1-10 FOAF trust module - http://trust.mindswap.org/trustOnt.shtml
Integer {0..infinity} Chimaera (Tarah, Huitema); Free Haven (www.freehaven.net, Dingledine) direct and meta trust; Li Gong system and direct trust; PGP's parameters (number of agents); Advogato's trust metric
Integer {1..infinity} Ueli Maurer's deterministic trust
Integer {-1..4} Abdul-Rahman/Hailes; Poblano (www.jxta.org/docs/trust.pdf)
Logical Binary (true, false) Cryptographic logics (Burrows/Abadi/Needham' BAN, Gong/Needham/Yahalom's GNY, Syverson/van Oorschot's SvO); Freenet (www.freenetproject.org); Lars Rasmusson/Sverker Jansson; P. Venkat Rangan.; SPKI
Logical trust(trustor,trustee,action,level) where level is in {-100;100} Grandison/Sloman's SULTAN
Logical trustBL(trustor,service,trustee,,depth,blacklist) where depth is in {0..infinity} + {*} (* for ) Giorgini/Massaci/Mylopoulos/Zannone
Logical formulas Demolombe/Jones logics; Walt Teh-Ming Yao's Fidelis
Matrix Table Yao-Hua Tan
Real [0;1] Ueli Maurer's probabilistic trust; Neurogrid (www.neurogrid.net, Samuel Joseph); Sierra's (sierra.openprivacy.org, OpenPrivacy) System trust; Castelfranchi/Falcone/Pezzulo's trustfulness
Real [0;1[ BBK (Beth, Borchedring, Klein) direct trust
Real ]0;1[ IST (Jamil, Sadri, Shiri)
Real [-1;1] Marsch (http://citeseer.ist.psu.edu/marsh94formalising.html); Sierra's (sierra.openprivacy.org, OpenPrivacy) interpersonal and self trust
Vector Tuple (each component in [0;1]) Josang's opinions (belief/disbelief/uncertainty/atomicity); Narendar Shankar/William A. Arbaugh; Golbeck/Hendler/Parsia (minimum, maximum, and weighted average trust); SECURE (support, inconclusive, contradict)
Vector Emotional Bank Account (EBA) Tuple of 3 fields in a given virtual currency (amount of money paid by the trustee in terms of actions; money lost due to these actions; some money, which is not yet known to be gained or lost) Trustee's EBA(100,12,4): the trustor has gained 100 trustos from this trustee, lost 12 trustos and 4 trustos are still not processed (http://www.cs.tcd.ie/publications/tech-reports/reports.04/TCD-CS-2004-37.pdf) ; the term Emotional Bank Account is from Stephen Covey's 7 habits of highly effective people