Associative Model of Data - Discussion

Discussion

In an associative database management system, data and metadata (data about data) are stored as two types of things:

  • Items, each of which has a unique identifier and a name.
  • Links, each of which has a unique identifier, together with the unique identifiers of three other things, that represent the source, verb and target of a fact that is recorded about the source in the database. Each of the three things identified by the source, verb and target may each be either a link or an item.

Here's how the associative model would use these two structures to store the piece of information Flight BA1234 arrived at London Heathrow on 12-Dec-05 at 10:25 am. There are seven items: the four nouns Flight BA1234, London Heathrow, 12-Dec-05 and 10:25 am, and the three verbs arrived at, on and at. Three links are needed to store the data. They are:

Flight BA1234 arrived at London Heathrow
... on 12-Dec-05
... at 10:25 am

The first link has Flight BA1234 as its source, arrived at as its verb and London Heathrow as its target. The second link has the first link as its source, on as its verb and the item 12-Dec-05 as its target. (A link that begins with an ellipsis "..." has the previous link as its source.) The third link has the second link as its source, at as its verb and 10:25 am as its target.

Here is an alternative way to write the same thing using parentheses:

((Flight BA1234 arrived at London Heathrow) on 12-Dec-05) at 10:25 am

An associative database may be regarded as comprising two tables: one for items and one for links. Each item and each link has an arbitrary number (called a surrogate) as an identifier:

Items
Identifier Name
77 Flight BA1234
08 London Heathrow
32 12-Dec-05
48 10:25am
12 arrived at
67 on
09 at
Links
Identifier Source Verb Target
74 77 12 08
03 74 67 32
64 03 09 48

Read more about this topic:  Associative Model Of Data

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