1. A method performed by a computing device for managing the lifetime of semantically-identified data, the method comprising: maintaining, by said computing device, a graph data structure in storage of said computing device, said graph data structure being defined by a graph data structure definition and having set of data items and relationships therebetween that are semantically identified, said graph data structure containing a semantic description associated with each said data item, each data item having a value; storing, by said computing device, lifetime information in at least one of said graph data structure and said graph data structure definition, said lifetime information describing the period during which at least one of said data item values in said graph data structure is valid; receiving, by said computing device, a consume request from a software system to receive updated values of said set of data items, said consume request including semantic descriptions of said data items; and when said value of one of said data items specified in said consume request becomes invalid: semantically resolving, by said computing device, said semantic descriptions of said requested data items included in said consume request and said semantic descriptions of said data items in said graph data structure; and electronically notifying said software system, by said computing device.