Applications in domains such as Multimedia, Geographical Information Systems, and digital libraries demand a completely different set of requirements in terms of the underlying database models. The conventional relational database model is no longer appropriate for these types of data.
The volume of data is typically significantly larger than in classical database systems. Finally, indexing, retrieving and analyzing these data types require specialized functionality not available in conventional database systems.
Objectives
To understand the various database models and their limitations To understand temporal management concepts, design, and challenges To understand the design & Implementation of temporal databases
Limitations of Conventional databases
Conventional databases typically consist of many tables, each of which is composed of a number of columns. The definition of those tables and columns determine the storage capabilities of the database, whereas the relations between the columns define the kinds of facts that can be stored in such a database. Those columns and relations determine the database structure that defines the expression capabilities of the database. Similar rules apply for the structure of data exchange files and thus for the information that is exchanged in electronic data files. This conventional database technology has some major constraints:
When data was not covered during the database design and thus is not included in the data model, then such data cannot be stored in the database nor exchanged via such a data file structure. Different databases have different data structures, which causes that data in one database cannot be integrated with data from other databases nor exchanged between databases without dedicated data conversion. A database modification or extension requires redesign of the database structure, modification of software and data conversion, which makes it a relatively complicated and costly exercise.
Another characteristic
international standards available or used for the content of the databases, being the data that is entered by its users. This typically means that local conventions are applied to limit the diversity of data that may be entered in those databases. As local conventions usually differ from other local conventions this has as disadvantage that data that are entered in one database cannot be compared or integrated with data in other databases, even if those database structures are the same and even if the application domain of the databases is the same.
Characteristics of a Gellish Database
A Gellish database does not have the semantic limitations that conventional databases have, because of the flexible and open Gellish language and because of its standard universal data structure (grammar), which is simple, computer and human interpretable. A Gellish database consists of one or more database tables, each of which has the same table structure.
The fact that those Gellish Database tables are standardized and universally applicable makes a Gellish database application independent. A standardized Gellish database table is universally applicable because it enables the application of the following two fundamental principles:
Explicit classification
classes, with an unlimited number of classes in a dictionary. The Gellish database table enables to store any kind of object; because any individual object can be introduced by specification of an explicit classification relation between the object and a class, whereas classes
from the very large number of classes that are already defined in the Gellish English Dictionary and if the proper class is not available it can be added by specification of a subtype-supertype relation with a direct supertype of the new class. This is fundamentally different from conventional databases that predefine the object types (classes) about which information can be stored by defining a limited number of entity types and attribute types in a fixed data model.
Explicit classification of relations (facts), by an extensible unlimited number of standardized relation types. The Gellish database table enables to store any kind of fact about any kind of object, because any fact is expressed by a relation, whereas those relations are explicitly classified by relation types that can be selected from the standardized relation types that are defined in the Gellish Dictionary or by relation types that are added to the dictionary as proprietary extensions. This is fundamentally different from conventional databases.