Unit 4 Reading Comments

Wikipedia – “Database”

If not every collection of data is a database then what are the other collections called?

If “stored data in a database is not generally portable across different DBMS,” should they be? As data becomes more important in scholarship, it would seem like some type of standardization to be interoperable to a high degree across DBMSs will be increasingly important. Later in Database Migration between DBMSs, they say “A database built with one DBMS is not portable to another DBMS,” but go on to talk about the ways in which it is possible to “migrate” and “transform” from one to another. I don’t get how it is possible (but tricky) and all not possible (put doable).

This article makes it sound as if while SQL is the (a?) standard for ANSI and ISO that it is not as useful as perhaps other languages. Is this an example of an early infrastructure adoption that is maybe not perfect, but is so ubiquitous that we cannot free ourselves of it?

Wikipedia – “Entity-relationship model”

See, Peter Chen, "The Entity Relationship Model: Toward a Unified View of Data"

Entity(-type)= physical object, event, or concept. Entity is only one instance of these things, but entity-type is the actual category that includes many instances.

Entities are the nouns, and the relationship is the verb. Ex.: Artist—Perform—Song. This is one instance, the entity-relationship is composed of  a set of instances.

http://www.phlonx.com/resources/nf3/

Normal Form (NF1) needs ”atomicity”: the indivisibility of an attribute into similar parts.

Does figure A-1 break atomicity, it has columns that contain repeating data, but it’s rows seem okay. I don’t see how fig. A-1 is really any different from B other than they filled in the repeating data. It seems like both have elements that make their rows unique. The answer is that it doesn’t and hence is broken up into several different tables until it does. 

This tutorial would be easier to follow if it included a database that I was manipulating. Also, if it began with showing the final product (fig. K) displayed next to A-1 I think it would help. Not that it would need to explain what exactly was different in the beginning, only show that we need to go from spreadsheet to database and they each look like this. Then they could go on to explain how that is accomplished and why each step is necessary. As it stands, I had to go back the beginning and re-read in order to really start to grasp what happened.