 Gabbay’s (1993, 1996) framework of labelled deductive systems exemplifies the information as code approach in manner very similar to the informationalised substructural logics of  section 3.1.  An item of data (note that Gabbay refers to both atomic and conditional information as data, in contrast to Dunn and Sequoiah-Grayson in the section above) is given as a pair of the form \(x : A\), where \(A\) is a piece of declarative information, and \(x\) is a label for \(A. x\) is a representation of information that is needed operate on or alter the information encoded by \(A\). Suppose that we have also the data-pair \(y : A \rightarrow B\). We may apply \(x\) to \(y\), resulting in the data-pair \(x + y : B\) In this case, a database is a configuration of labelled formulas, or data-pairs (Gabbay 1993: 72). The labels and their corresponding application operation are organised by an algebra, and the properties of this algebra will impose constraints on the applications operation. Different constraints, of “meta-conditions” as Gabbay calls them (Gabbay 1993: 77), will correspond to different logics. For example, if we were to ignore the labels, then we would have classical logic, if we were to accept only the derivations which used all of the labelled assumptions, then we would have relevance logic, and if we accepted only the derivations which used the labelled assumptions exactly once, then we would have linear logic. Labels are behaving very much like possible worlds here, and the short step from possible worlds to information states makes it obvious how it is that the meta-conditions on labels may be captured by structural rules. 