Editing Network model (section)

==Overview==
While the [[hierarchical database model]] structures data as a [[Tree data structure|tree]] of [[Record (computer science)|records]], with each record having one parent [[Record (computer science)|record]] and many children, the network model allows each record to have multiple parent and child records, forming a generalized graph structure. This property applies at two levels: the schema is a generalized graph of record types connected by relationship types (called "set types" in CODASYL), and the database itself is a generalized graph of record occurrences connected by relationships (CODASYL "sets"). [[cycle (graph theory)|Cycle]]s are permitted at both levels. Peer-to-Peer and Client Server are examples of Network Models.

The chief argument in favour of the network model, in comparison to the hierarchical model, was that it allowed a more natural modeling of relationships between entities. Although the model was widely implemented and used, it failed to become dominant for two main reasons. Firstly, IBM chose to stick to the hierarchical model with [[semi-network]] extensions in their established products such as [[Information Management System|IMS]] and DL/I. Secondly, it was eventually displaced by the [[relational model]], which offered a higher-level, more declarative interface. Until the early 1980s the performance benefits of the low-level navigational interfaces offered by hierarchical and network databases were persuasive for many large-scale applications, but as hardware became faster, the extra productivity and flexibility of the relational model led to the gradual obsolescence of the network model in corporate enterprise usage.