ratio of energy efficiency. This is to say that it is defined as the ratio of emergy input to energy output. Original version:: Development However, it was realised that the term "energy output" refers to both the useful energy output and the non-useful energy output. (Note: that as given by P.K.Nag, an alternative name for 'useful energy' is 'availability' or exergy, and an alternative name for 'non-useful energy' is 'unavailability', or anergy (Nag 1984, p. 156)). But as E.Sciubba and S.Ulgiati observed, the notion of transformity meant to capture the emergy invested per unit product, or useful output. The concept of Transformity was therefore further specified as the ratio of "input emergy dissipated (availability used up)" to the "unit output exergy" (Sciubba and Ulgiati 2005, p. 1957). For Jørgensen (2000, p. 61) transformity is a strong indicator of the efficiency of the system. Revised version: or (after Giannantoni 2002, p. 8). Substituting in the mathematical definition of emergy given in that article. Contemporary development Two transformities Albertina Lourenci and João Antonio Zuffo from the Department of Electronic Systems Engineering at São Paulo have posited that there are two transformity values; and (Lourenci and Zuffo 2004, p. 411). : compensates for the dissipation of exergy, and is defined in words as the Quality Factor which takes into account the emerging Quality associated to other forms of Energy : accounts for the increase of Transformity as a consequence of the Emergy generated by the Source Terms of the Universe Under these definitions "emergy" can always be structured as follows: References B.R. Bakshi (2000) 'A thermodynamic framework for ecologically conscious process systems engineering', Computers and Chemical Engineering 24, pp. 1767–1773. S.Bastianoni (2000) 'The problem of co-production in environmental accounting by emergy analysis', Ecological Modelling 129, pp. 187–193. S.Bastianoni, F.M.Pulselli, M.Rustici (2006) Exergy versus emergy flow in ecosystems: Is there an order in maximizations?', Ecological Indicators 6, pp. 58–62 S.Bastianoni, A. Facchini, L. Susani, E. Tiezzi (2007) 'Emergy as a function of exergy', Energy 32, 1158–1162. M.T. Brown and S. Ulgiati (2004) Energy quality, emergy, and transformity: H.T. Odum's contributions to quantifying and understanding systems, Ecological Modelling, Vol. 178, pp. 201–213. T.T.Cai, T.W.Olsen and D.E.Campbell (2004) Maximum (em)power: A foundational principle linking man and nature', Ecological Modelling, Volume 178, Issue 1–2, pp. 115–119. D.E.Campbell (2001) Proposal for including what is valuable to ecosystems in environmental assessments', Environmental Science and Technology, Volume 35, Issue 14,