@article {380, title = {Model Theory of XPath on Data Trees. Part {I:} Bisimulation and Characterization}, journal = {J. Artif. Intell. Res. {(JAIR)}}, volume = {53}, year = {2015}, pages = {271{\textendash}314}, doi = {10.1613/jair.4658}, url = {http://dx.doi.org/10.1613/jair.4658}, author = {Diego Figueira and Santiago Figueira and Carlos Areces} }