Week Four:

REQUIRED READING NOTES

Database (Wikipedia)
http://en.wikipedia.org/wiki/Database

• Defined as an organization collection of data. It is organized to model aspects of reality that supports processes requiring information. (example of being able to find a hotel with vacant rooms on a website)
• The term "database" refers to data itself and its supporting data structures. They are created to operate large quantities by storing, retrieving, and managing information.
• DBMS - database management systems - are designed to interact with users, applications, and the database system itself to analyze and decipher data. General purpose DBMS allow definition, creation, querying, updates, and administration of databases. (Oracle. Microsoft Access. FileMaker Pro.)
• There are four different types of databases: Operational, Specific, External, Hypermedia.
• Database servers are multiprocessor computers with a lot of memory and RAID disk arrays for storage. (RAID is the recovery tool for data)
• Commonly used to hold administrative information and specialized data (engineering data, economic models) --> computerized library systems are database models
• Humanities focus on general-purpose DBMS - aims to meet the needs of as many applications as possible. AS OPPOSED TO special-purpose databases such as an email system. 
• Current database systems are based on an original model, called the relational model, proposed in 1970 by Edgar F. Codd. Today's dominant database language, standardized SQL for the relational model, sets a precedent for other data models.
• Can be classified by their content, such as bibliographic, document-text, statistical, or multimedia objects. May also be classified by application area: accounting, compositions, movies, banking, insurance. ALSO can be classified by technical aspect (database structure).
• Various characterizations of databases include -
• in-memory database: primarily resides in main memory, backed up by non-volatile computer data storage.
• active database: event-driven architecture to respond to inside and outside the database.
• cloud database: information held in a virtual network. cloud computing
• data warehouses: archived data from operational databases. also from external sources
• deductive database: combining logic programming with relational databases
• distributed database: both data and the DBMS span over multiple computers
• document-oriented database: designed to store, retrieve, and manage document information
• embedded database: system where DBMS is tightly integrated with application software
• end-user databases: data developed by individual end-users. examples include collections of spreadsheets, documents, presentations, and multimedia. 
• federated database: handled as a single database by a federated database management system.
• graph database: uses graph structures to represent and store information.
• hypermedia database: any word or text representing an object can be hyperlinked
• knowledge base: special for knowledge management, provides means for a computerized collection and retrieval of knowledge.
• mobile database: carried on or synchronized from a mobile computing device
• operational database: stores detailed data about operations of an organization. customer databases
• parallel database: looks to improve performance for loading data and evaluating queries.
• spatial database: stores data with multidimensional features "where is the closest hotel to me?"
• terminology-oriented database: customized for a specific field

Entity-relationship model
http://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model

• This is defined as a data model for describing the data or information aspects of a business domain. It lends itself to being implemented in a database. basically, it is the things and the relationships that exist among them and databases.
• Developed in 1976 by Peter Chen. 
• described as a systematic way to describe and define a business process. Modeled as components (things) + linked through relationships to express dependencies and requirements between them. 
• ER models are implemented as a database. There are THREE levels of ER models to develop:
• Conceptual data model - highest level of ER model. establishes the overall scope that is to be included. defines master reference data entities that are commonly used by the organization.
• Logical data model - does not require a conceptual ER. contains more detail than the conceptual. developed independent of technology into which it is implemented.
• Physical data model - normally developed to be instantiated into a database. used to design modifications to the relational database objects and to maintain structural metadata.
• Entity is defined as the thing capable of an independent existence that is uniquely identified. may be a physical object, an event such as a sale, or a concept. 

Database Normalization Process
http://www.phlonx.com/resources/nf3/

• This is a guide for beginners who are looking to grasp the concept of database normalization process.
• Uses the example of an invoice to level it to the Third Normal Form. also constructs an entity relationship diagram (ERD) throughout the tutorial.
• Normalization is a natural way of perceiving relationships between data and no special skill in mathematics or set theory is required.
• Three normal forms of database construction:
• No repeating elements or groups of elements.
• groups of rows are called a database row. 
• atomicity - the indivisibility of an attribute into similar parts.
• database columns are referred to as attributes
• a primary key is a column, or a group of two columns, that uniquely identify each row.
• two columns that uniquely identify each row are used as the table's primary key. although they are in different columns, they are treated as a single unit. called concatenated
• No partial dependencies on a concentrated key.
• this means a table that for each table that has a concatenated primary key, the column in the table is not part of the key must depend on the entire concatenated key for existence.
• No dependencies on non-key attributes.
• foreign key restores relationships in an orders table. essentially, it is the column that points to the primary key in another table.

Thoughts 

The terms from this week were very complicated to me because I have very little understanding of information technology. However, I think Wikipedia's definitions and examples have helped me to better understand what a database is and the entity-relationship model. It's definitely a very boring topic, but I was surprised to see how many different databases exist. As a student, I'm really only familiar with the campus computing database and I think that this has been most challenging so far this year. I do not feel that our third assigned reading, the database tutorial, was helpful. A lot of the information are terms that I have never worked with and I had a hard time connecting to the information.

Questions 
 
1. What types of databases would a student in higher education come into contact with?