Saturday, August 5, 2017

This Week



1. Database Truth of the Week

"Semantic correctness: every interpretation of the symbols (meaning assignment and truth value assignment) that makes the axioms true, makes the theorems true. When we extend a logical data model with semantics (specific to the subject matter and its "business" rules) via constraints, those constraints become axioms that must be true." --David McGoveran

Tuesday, August 1, 2017

Structure, Integrity, Manipulation: How to Compare Data Models




The IT industry operates like the fashion industry: every few years -- and the number keeps getting smaller -- a "new" data technology pops up, with vendors, the trade media and various "experts" all stepping over each other to claim that it'll "revolutionize your business" and unless you jump on the bandwagon, you'll be "left behind." But time and again these prove to be fads lacking a sound foundation. Huge resources are invested in migrations from fad to fad, rather than in productive work (Don't believe the hype about Hadoop usage, Basta, Big Data It's Time to Say Arrivederci). Remember?
"Hadoop seems to take over relational database, as Hbase can store even unstructured data whereas relational data warehouse limits to structured data ... handles traditional structured data just fine, albeit in a different way than a RDBMS ... EDW vendors [will] incorporate Hadoop framework into their core architectures to enable advanced and high performance analytics."

Sunday, July 30, 2017

Integrity Is Not Only Referential: DBMS vs Application Enforced Constraints



Note: This is 07/30/17 rewrite of a 11/11/12 post to bring it line with McGoveran formal exposition of Codd's real RDM [1] and its interpretation.

 

There is nothing wrong per se with the question in last week's picture, namely:
"Can I ask whether people make use of the functionality provided by the database to ensure adequate data quality. Secondly do people apply this retrospectively as seems quite reasonable to me when a data problem is identified and the source data cleaned up--to do so could prevent future errors. There appears to be a tension between this sort of implementation and at least a perception of flexibility as database changes would be required should additional allowable values be required." --LinkedIn.com
except that it's about time such questions are no longer asked. Unfortunately, they are evidence of the persistent lack of foundation knowledge in the industry for more than five decades. Such knowledge would have obviated such questions.

Sunday, July 23, 2017

This Week



1. Database Truth of the Week

"And [AI] weaknesses there are. Watson requires many months of laborious training, as experts must feed vast quantities of well-organized data into the platform for it to be able to draw any useful conclusions. And then it can only draw conclusions based upon the body of data, or ‘corpus’ (plural: ‘corpora’) that it has been trained on. The ‘well-organized’ requirement is especially challenging for Watson, as unprepared data sets are typically insufficient. As a result, Watson customers must hire teams of expert consultants to prepare the data sets, a time-consuming and extraordinarily expensive process." --Is IBM's Watson a Joke?

Sunday, July 9, 2017

This Week



1. Database Truth of the Week

"For the operations of a formal system to have inverses within some specific use of that system (like a specific application):
  • The basic elements must be orthogonal (independent), hence the Principle of Orthogonal Design;
  • The combination of basis elements and operations must be expressive enough to represent every aspect of the subject matter, hence the Principle of Expressively Complete Design;
  • And, at the same time, not so expressive that there is more than one way to express each aspect of the subject matter, hence the Principle of Representation Minimality Design.
The basic elements of a relational database is the relation. Adherence to these principles ensure thatthere is a unique relational expression for every aspect of the subject matter--either a base relation or a derived relation--and if there are two ways to derive a derived relation, then those two expressions are provably equivalent (i.e., the differences are merely syntax and never meaningful)." --David McGoveran

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