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Considered data model is a further development of so called ER-model (entity-
relationship). Like the ER-model , semantic model deals with entity (or object)
and relationship notions. Object is an information reflection of real object or event,
while the relationship reflects various relations between the objects such as
possession, generalization, logical relations, etc.
Separate description of object and relationship attributes is customary for data models
dealing with relation between objects notion. In ER-model, for example, an object is
described by a structure representing properties table, its relations to other objects
being defined separately. Major distinctive feature of the semantic data model in
comparison with its predecessors is a new approach to object and relationship
correlation. First of all, elementary entity notion is introduced here. It is an pseudo-
object defined by a sole attribute only. All the elementary entities realizations are sets
treated as some parameter potential values domains. That notion, therefore, is virtually
equal to domain conception.
In fact any object is defined as an aggregate of references to other objects as well as to
elementary entities. Formally such a model may be presented as follows.
There exists some set of the domains (elementary entities):
{ D1, D2, ..., DN }
The domains set constitutes an information foundation of database resting upon the
model involved.
Relation, in a general sense, is considered to be a relationship defined at domains set:
R = { [d1, d2, ..., dN ],
where d1 is element of D1, d2 - element of D2 and so on }
Hence an entity or object can be presented as some relations aggregate:
E = { {R'1, R'2, ..., R'K},
where R'i belongs to relations set {R'} with domains;
{R1, R2, ..., RL},
where Ri belongs to relations set {R} with objects }
The objects' set along with their relations constitutes semantic (sense) contents of
hypothetical database.
Inside the object every relation gets an unique name for further identification. Access
to any relation is possible only via the object it belongs to. This condition ensures the
database information logical integrity and by no means constrains the data access,
because same domain may participate in unlimited number of relations belonging to
various objects.
Described data and their relations modeling scheme makes it possible to establish
object relations of any complexity. It means that the involved model enables us to
reflect any logical relations that may really exist in a given application field.
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