1. Database truth of the week
"Relvars introduce a concept of assignment, which has no counterpart in either FOPL or set theory. If you add it to those formalisms you introduce computational completeness, which destroys both decidability (the existence of a general algorithm by which you can determine if an expression is or is not logically valid) and the guarantee that there exists a (query) evaluation procedure that will halt (the existence of a general algorithm by which you can evaluate the truth or falsity of every instantiated predicate expression given those instantiations from any given database). Therefore we must forbid relvars." --David McGoveran
2. What's wrong with this database picture?
"Many data and information modelers talk about all kinds of keys (or identifiers. I'll forego the distinction for now). I hear them talk about primary keys, alternate keys, surrogate keys, technical keys, functional keys, intelligent keys, business keys (for a Data Vault), human keys, natural keys, artificial keys, composite keys, warehouse keys or Dimensional Keys (or Data Warehousing) and whatnot. Then a debate rises on the use (and misuse) of all these keys ... The foremost question we should actually ask ourselves: can we formally disambiguate kinds of keys (at all)? Of all kinds of key, the primary key and the surrogate key gained the most discussion."
"If we take a look at the relational model we only see of one or more attributes that are unique for each tuple in a relation -- no other formal distinction is possible. When we talk about different kinds of keys we base our nomenclature on properties and behavior of the candidate keys. We formally do not have a primary key, it is a choice we make and as such we might treat this key slightly different from all other available keys in a relation. The discussion around primary keys stems more from SQL NULL problems, foreign key constraints and implementing surrogate keys. --Martijn Evers, Kinds of Keys: On the Nature of Key Classifications, dm-unseen.blogspot.com
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3. To Laugh or Cry?
"The database world isn’t packaged with mind-bending announcements on a weekly basis, but over the course of a year it never fails to surprise me how many new things we do see, and how unrelenting the progression is. 2017 was no exception, so I want to reflect on some of the interesting new releases including a transactional graph database, a geo-replicated multi-model database, and a new high performance key/value store." --Peter Cooper, A Look at Ten New Database Systems Released in 2017
4. Publications
- NEW! The Key to Relational Keys: A New Perspective, forthcoming.
- THE DBDEBUNK GUIDE TO MISCONCEPTIONS ABOUT DATA FUNDAMENTALS, my latest book, is available to order here (Reviews: Craig Mullins, Todd Everett, Toon Koppelaars, Davide Mauri).
- Logical Symmetric Access, Data Sub-language, Kinds of Relations, Database Redundancy and Consistency, paper #2 in the new UNDERSTANDING OF THE REAL RDM series, is available for ordering here.
- Interpretation and Representation of Database Relations, paper #1 in the new UNDERSTANDING OF THE REAL RDM series, is available for ordering here.
5. Housekeeping:
To work around Blogger limitations, the labels are mostly
abbreviations or acronyms of the terms listed on the FUNDAMENTALS page. For
detailed instructions on how to understand and use the labels in conjunction
with the FUNDAMENTALS
page, see the ABOUT
page. The 2017 and 2016 posts, including earlier posts rewritten in 2017 are
relabeled. As other older posts are rewritten, they will also be relabeled, but
in the meantime, use Blogger search for them.
6. Oldie But Goodie
DataBase Debunking clarifications
And Now for Something Completely Different: The PostWest - The Decadence Stage
Must Read of the Week
- American social collapse is a catastrophe of human possibility without modern parallel
- Why breaking up Amazon, Google, Apple, and Facebook could save capitalism
- How Technology Is Creating a Generation of Adult Babies
Analysis
- End of days Is Western civilisation on the brink of collapse
- This is how democracies die
- The Surveillance State In 2018
- Trust Is Collapsing in America
- Higher Education Is Drowning in BS
- 5 Ways Capitalist Logic Has Sabotaged the Scientific Community
- Not just about Trump, but a product of the same culture that produced Trump
- The People That Capitalism Makes
- On the Phenomenon of Bullshit Jobs
- How long will the rich be willing to share the roads with the poor
- Silicon Valley and the Threat to Democracy
- Silicon Valley isn’t just disrupting democracy—it’s replacing it
- Facebook is a 'living, breathing crime scene
- Technology’s Broken Promises: Startups, Capitalism, and the Destructive Force of a Culturally Bankrupt Industry
- Google Can No Longer Innovate, Is Mired in Politics, and Has Become Absolutely Competitor-Focused
Evidence
- Financial Literacy: Two-Thirds of Americans Can't Pass Basic Test
- Life expectancy in America has declined for two years in a row
- About That Joint Marijuana Start-Ups Pass
- Adult-teen robbery crew arrested amid new wave of 'gang' crime
- America's new deadliest drug is fentanyl
- Peeved by price gouging and shortages, hospitals will now make their own drugs
- Senate to vote to renew NSA's internet surveillance program
- The Fall of Travis Kalanick Was a Lot Weirder and Darker Than You Thought
- Facebook Only Cares About Facebook and acting against the public good
- The Internet Is Enabling a New Kind of Poorly Paid Hell
- The Long-Term Care Crisis Premiums Exploding, Leaving Seniors With “An Awful Choice”
- The New Age of Astrology
- The Students Who Don’t Believe College Is an Option
- The U.S. Drops Out of the Top 10 in Innovation Ranking
- Warrantless phone, laptop searches at the US border hit record levels
- Why does it cost $32,093 just to give birth in America
- How Our Government Is Failing Both Patients and Nurses
Pinch Me
- U.K. Appoints a Minister for Loneliness (Build a society, don't add yet another parasitic bureaucrat).
- The Irony of the Pope Decrying Fake News
Upside Down and Backwards
- Amazon, City Killer
- At Amazon's New Checkout-Free Store, Shopping Feels Like Shoplifting
- Cash prizes for bad corporate citizenship, Amazon edition
- The Problem With Courting Amazon
- but Amazon Scores Two More $5+ Billion Bids
- and Bezos laughs all the way to the bank
Book of the Week
THE PUPPET MASTERS
Video of the Week
Nothing to Hide
Site of the Week
Open Markets Institute
Fuck the Joos: The 2000 Years Old Universally Acceptable Only Hatred Left
- (On Trump’s comment) A different media reaction when Israel was described as “shitty”
- UN Helpless Against Real Genocide, Because It's Too Busy Blaming the Jews For False Ones
- Obama posed with Louis Farrakhan the Congressional Black Caucus helped repress the photo
- The Fantasy of an International Jerusalem
- Diaspora Ministry sees troubling trends in anti-Semitism worldwide
- Human rights are universal, Amnesty. Even Jewish rights
- Cleveland-area synagogues hit with anti-Semitic voicemails
- Republican Senate hopeful linked to Holocaust deniers
- Website offers yellow star patches for 'persecuted' gun owners
- Racist, anti-Semitic fliers dropped in Virginia town
- Paul Nehlen Is an Anti-Semitic Clown
- EU mum on Abbas speech because 'we don't comment on comments'
- Jews said barred from UK campus lecture on Israel’s ‘reproductive sabotage’
- Corbyn Holocaust memorial statement omits Jews, anti-Semitism
- French broadcaster blasted for prime-time Holocaust joke
- French Jewish group demands action following rash of anti-Semitic incidents
- German lawmakers vote to install commissioner to fight anti-Semitism
- Merkel lets One Million Anti-Semites In Then Declares 'Ongoing need to protect Jewish institutions 'a disgrace'
- Amsterdam synagogue, Jewish hospice targeted in vandalism incidents
- Austrian arrested for yelling 'Heil Hitler' at rabbi at concentration camp site
- In jail, Austrian historian writes book slamming Holocaust restitution system
- Polish neo-Nazi Hitler celebration sparks revulsion, debate
- Poland Tries to Deny Participation in Holocaust by Law
- Greek Jews condemn neo-Nazi vandalism of Thessaloniki Holocaust memorial
- 5 arrested in connection with firebomb attack on Tunisia synagogue
Nice People - Let's Give them a State: The Myth of the Palestinian Nation
- Stop ‘understanding’ the Palestinians
- Fatah deputy chief US has never given Palestinians anything substantial
- Trump, Pence effigies hanged and burned in video on Palestinian TV station
- Washington has been the largest international donor to the PA since the early 90's with over $5 billion in USAID funds alone
- US Secy of State Fights for $700 Million in Aid to PA
- Amid funding cut fears, PA purchases $50 million private jet for Abbas
- Hamas Stole $700 Million in Aid to Gaza, Palestinian Authority
- Palestinians to U.S.: Shut up and give us the money!
- How Aid To Palestinians Hurts - Not Helps - The Peace Process
- Donald Trump's Middle East Policy Breaks Status Quo. Good
Note: I will not publish or respond to anonymous comments. If you have something to say, stand behind it. Otherwise don't bother, it'll be ignored.
Regarding the confusing blogspot statement "...We formally do not have a primary key, it is a choice we make and as such we might treat this key slightly different from all other available keys in a relation....":
ReplyDeleteThe word "formally" is misused and suggests a limited perspective which by itself is almost useless in practice. A data design is the formal specification of the input to a formal system, or formal program if you like.
No discussion of primary keys is complete without dealing with how they are used by a system.
For example in appendix B of his 1990 book Codd gave this exercise among others:
"The notation F -> G means that the DBMS must support F if it is to provide full support for G. ... 3. Let F be primary keys and G be view updatability. Show that F -> G."
People who write about the use of primary keys need to answer this exercise. A clue is the concept of functions as used in Codd 1970 and the meaning of an inverse function.
( I agree with McGovern that the term "view updatability" should be deprecated and replaced with something like relation or database updatability.)
The writer is correct that we do make choices. One that is rarely written about is choosing primary keys to be a fundamental data design starting point or concept. This is convenient but is theoretically not required by relational algebra which could provide equivalent system behavior through derived relations. I don't advocate such an implementation, only this second exercise which puts the concept in a more concrete light.
Wait for my next 2 posts on the subject and my forthcoming paper.
DeleteRegarding relvars and assignment, the 1985 book Structure and Interpretation of Computer Programs which I believe is still available online at the MIT website gave more concrete explanation in terms of application language of the computational problems introduced by language assignment.
ReplyDeleteRelvars can be a system implementation device which means they only need to be forbidden at the user language level. But more needs to be said because some relvar supporters claim to have produced truly relational dbms's with languages that allow user access to relvars that treat the specification, in Codd's terms the expression, of a subset of a relation as having the same predicate as the relation. Not only does this duplicate the error SQL makes with rows and tables but it is actually taught at the college level.
The subset is a relation in its own right and its expression is as Codd put it, equivalent to a class of wff's. In practice it is generally not the case that that class is the same class as the expression of the original relation. The implications are far-reaching but generally unrecognized by the database industry.