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Topic: kinds of relationships between data
topics >
computer science >
information >
database queries, joins, and relational algebra
Topic:
entity-relationship database model
Topic:
facts as relationships between entities
Topic:
fundamental concepts such as type, attributes, relationships are all the same
Topic:
representing a relationship
Summary
Data may be related in many ways. It may be constrained, ordered, divided into equivalence classes, one-to-many, or one-to-one. It may be derived or computed from other data. (cbb 11/07)
Subtopic: derived information
Quote: a relationship may be optional or mandatory for all objects in a domain [»kentW_1978] Quote: a system may allow only one relationship between each pair of domains [»kentW_1978] Quote: a relationship may be transitive [»kentW_1978] Quote: a relationship may be symmetric; but such relationships are seldom supported [»kentW_1978] Quote: a relationship can be anti-symmetric [»kentW_1978] Quote: a relationship may be composed from other relationships [»kentW_1978] Quote: a relationship may be a subset of another relationship [»kentW_1978] Quote: a one-many relationship may have a maximum size [»kentW_1978] Quote: even though both roles of a relationship can have the same domain, a thing may or may not be related to itself [»kentW_1978]
Subtopic: relationship by computation
Quote: data which can be extracted from a system is not necessarily stored in the system [»kentW_1978, OK] Quote: minimal set predicate: the set of things having relationship x to object y [»kentW_1978] QuoteRef: grayJC_1973 ;;170 have converse of a relation eg children^name-set generates the set of parents whose children are in name-set
Subtopic: derivation is not definition
Quote: every computable procedure represents a relationships [»kentW_1978] Quote: an ordering between objects is a computed relationship [»kentW_1978] Quote: computed relationships are not modifiable; instances can be infinite, without attributes or relations [»kentW_1978]
Quote: even though uncle is derived from father and brother, sometimes only know the uncle relationship
[»kentW_1978]
Topic: database queries, joins, and relational algebra (34 items)
Topic: entity-relationship database model (22 items)
Topic: facts as relationships between entities (22 items)
Topic: fundamental concepts such as type, attributes, relationships are all the same (37 items)
Topic: representing a relationship
(28 items)