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The databases that dominated the industrial scene prior to the emergence of relational designs—IBM’s IML, GE’s IDS, the CODASYL systems—were described as follow
by twoodfin 5y ago
The databases that dominated the industrial scene prior to the emergence of relational designs—IBM’s IML, GE’s IDS, the CODASYL systems—were described as following a “network” model, which didn’t have much conceptual distance from what today we’d call a “graph” model.
They were largely replaced with relational systems for more or less exactly the reason Codd laid out in his classic paper[1]: If efficient processing of logical operations depends on a predetermined physical structure of data, the range of practical applications for your database is severely constrained.
That suggests that the proper niche for graph databases contains those applications with a predefined set of highly recursive operations, which is more or less where we find them today.
[1] http://db.dobo.sk/wp-content/uploads/2015/11/Codd_1970_A_relational_model.pdf http://db.dobo.sk/wp-content/uploads/2015/11/Codd_1970_A_rel...
- j-pb 5y agoYet a relational database in 5th normal form is equivalent to a RDF-Like first order Triple graph. A lot of network databases store graphs as pointer-bogs which are hard to process and query, but that does not diminish the virtues of the graph model itself or preclude a representation based on joins. I'd argue that a 5th normal form graph representation contains a lot less implementation detail and is a lot more flexible than a regular old buch of tables.
- AlecSchueler 5y agoCould you recommend some resources for reading more/learning about Nth normal forms?
- alex_anglin 5y agoWikipedia is a good start: https://en.wikipedia.org/wiki/Database_normalization https://en.wikipedia.org/wiki/Database_normalization
- zozbot234 5y ago> Yet a relational database in 5th normal form is equivalent to a RDF-Like first order Triple graph. Not quite. The definition of 5NF depends on real-world constraints on valid combinations of attributes in the database; it has nothing to do with any pre-defined data model such as RDF. There can be "wide", horizontally-modeled tables (quite unlike the RDF model) which are in 5NF simply because no real-world constraints apply to the data beyond those that are implied by the candidate keys.
- brightball 5y agoWow. First time I’ve heard of a normal form above 3rd. Guess I need to read up.
- HideousKojima 5y agoFWIW, there's very little practical reason to normalize your DB beyond the third normal form (or technically the Boyce-Codd normal form, which your DB will probably already meet if it's in 3NF)
- jbritton 5y agohttp://graphdatamodeling.com/resources/rettigNormalizationPoster.pdf http://graphdatamodeling.com/resources/rettigNormalizationPo...
- zanethomas 5y agoI worked with a hierarchical database system in the late 80s. Nightmare. <g>
- amitport 5y agoI assume you mean IBM's IMS. I don't think it was replaced for lack of flexibility. AFAIKT it was replaced (by those who could replace it. There are many that still use it. Like banks) because IBM didn't let it progress, basically froze it in the cobol era, tied it with their hardware, and continued to cash-in as long as they could. Unlike some sister comment, I think it was conceptually great... Only the tooling and ecosystem were/are terrible.