Since its inception in the 1990s, the boundaries between GIScience and cognate disciplines are contested, and different communities might disagree on what GIScience is and what it studies. In particular, Goodchild stated that "information science can be defined as the systematic study according to scientific principles of the nature and properties of information. Geographic information science is the subset of information science that is about geographic information."[6] Another influential definition is that by geographic information scientist (GIScientist) David Mark, which states: