E-model: Event-based graph data model theory and implementation

The necessity of managing disparate data models is increasing within all IT areas. Emerging hybrid relational-XML systems are under development in this context to support both relational and XML data models. Typical hybrid systems are based on one type of database system, with support added to accommodate the other data model. However, there are ever-growing needs for adequate data models for texts and multimedia, which are applications that require proper storage, and their capability to coexist and collaborate with other data models is as important as that of a relational-XML hybrid model.;This work proposes a new data model named E-model that supports rich relations and reflects the dynamic nature of information. This E-model introduces abstract data typing objects and rules of relation that support: (1) the notion of time in object definition and relation, (2) multiple-type relations, (3) complex schema modeling methods using a relational directed acyclic graph, and (4) interoperation with popular data models.;Implementing a database system for a new data model takes good efforts for evaluation. The E-model structures first proposed in theories are materialized as database storage objects. To free the E-model from the back-end system, object identities are encapsulated in a unified data type named an e-node. Relations between sets of e-nodes conform to the temporal flow to capture information dynamics.;This work describes the complete data model design process from an abstract data modeling rule design to actual database system implementation. To implement the E-model prototype, extensive data operation APIs have been developed on top of relational databases. In processing dynamic queries, our prototype achieves an order of magnitude improvement in speed compared with popular data models. Based on extensive E-model APIs, a new language named EML is proposed. EML extends the SQL-89 standard with various E-model features: (1) unstructured queries, (2) unified object namespaces, (3) temporal queries, (4) ranking orders, (5) path queries, (6) semantic expansions, and (7) natural joins. The Emodel system can interoperate with popular data models with its rich relations and flexible structure to support complex data models. It can act as a stand-alone database server or it can also provide materialized views for interoperation with other data models. It can also co-exist with established database systems as a centralized online archive or as a proxy database server.;The problem is then whether relational, XML, or current hybrid database systems are flexible enough to accommodate additional text and multimedia data models. Although raw data type of texts involve simple characters, their document structures and relations between texts are not simple at all. Multimedia poses rather simple relations between data objects, but spatio-temporal variations in content complicate efforts to deal with this type. When multimedia and texts are merged for multimedia information service, then the complexity of content management rapidly exceeds the capabilities of even hybrid databases.;The current E-model prototype system was implemented on top of a relational database. This allows significant benefits from established database engines in application development. However, because of E-model's graph-based architecture, a graph walk on an E-model needs a sequence of joins which relational database systems, do not support efficiently. Our next research topic thus will be to develop an E-model hybrid database storage engine optimized for E-model architecture.