When transaction time is one of the supported properties, special semantics for update should be enforced to accommodate transaction time. In a transaction-time database the database is trusted to enforce these semantics. On the web, no such trusted mechanism is available for updates. However, individual sites or even collections of pages within a site can be archived to correctly support transaction time. Because of the flexibility of our framework, information from pages that support transaction time can be freely mixed with information from pages that do not.
In this section, we describe the constraints that should exist to correctly support transaction time, but leave open the issue of how these constraints are enforced on update. An update can be either at the data level, consisting of a change to an edge, label, or node, or at the meta-data level, consisting of the addition of a property. We discuss each kind of modification in turn.