Transcript lecture2
LIS 557 Database Design and Management William Voon Michael Cole Spring '04 Conceptual Foundations 29 January 2004 “Measure twice, cut once.” What is a database? ● Database: an organized body of related information A database has a purpose, so one must think: How will it be used? Who will use it? DB Characteristics ● Static ● Dynamic – ● The data in the system is variable Evolving – A growing database can be either static or dynamic Domains ● Domain: – a collection of groups of data elements that relate to the class we want the database to represent. Taken together, the domain elements allow one to express every possible situation of interest within the database A Recipe RU Red Ale All Grain Red Ale 6.5# Pale Malt 1.5# Pilsen Malt 6 oz Crystal Malt (800 Lovibond) 6 oz Crystal Malt (200 Lovibond) 4 oz Chocolate Malt 4 oz Wheat Malt Hops Northdown 4.7 HBU Bittering Cascade 30 minutes 6 HBU Flavor Mt. Hood 15 minutes 6 HBU Flavor/Aroma Irish Moss 15 minutes Wyeast 1084 Mash grains with 1 qt. water/LB. of grains at 156 F for 90 minutes or until conversion complete. Sparge with 170 F water for 60 minutes. Boil for 15 minutes and then add the bittering hops (Northdown); boil for 30 minutes and add flavor hops (Cascade), boil for 15 minutes and add flavor/aroma hops (Mt. Hood) and Irish Moss, boil for 15 minutes; chill to pitching temperature (70 F) and pitch yeast. Prime with 2/3 cup corn sugar dissolved in 1 pint of boiling water. What are the groups of elements in the domain of beer ingredients? Exercise ● ● Take a personal interest or hobby and identify the groups of elements that make up a domain, or Think of a special collection, what elements make up the domain for the collection? What is a Database Management System (DBMS)? ● DataBase Management System (DBMS): a software system supporting the creation, use and maintenance of a database DB vs. DBMS ● ● DBMS manages and exposes the database to its users The database fixes what is possible, while the DBMS determines what is actually available What are the essential goals of a DBMS? ● What must a DBMS accomplish? – Keep data around (persistent) – Keep it safe – Answer queries about data – Ensure data integrity – Allow modification of data – Control access to data Data and Information ● Complex question ● For our purposes: – Data: an elemental unit (a number, a word) that requires interpretation to be meaningful – Information stands on its own, that is one would say it is meaningful even without interpretation Notice that the context of use matters! - Imagine a database of historical documents Why a database? ● ● Consider some of the things a DBMS is supposed to do – Persistence – Answers to queries – Modification Why can't we do it all with information? – Well we can, sort of ..... The Bank of Springfield ● ● Computerized, but everybody's account information is stored in a word processing document. – e.g. ' – Account 124 # owned by # Montgomery Burns # has a balance of #$1211943.07' Account 123 # owned by # Homer Simpson # has a balance of #$321.17 Suppose it meets all of the basic criteria of a DBMS, so what's not so great about the BoS system? Databases Pros and Cons ● ● Taking a data perspective has huge advantages: – Economy – Speed – Scalability But, there are also some disadvantages: – Interpretation must be supplied – Getting answers to real questions is not so easy Database Systems ● ● Evolution driven by the structure of the data relationships: – Hierarchical (tree structure) – Network – Relational (table structure) Most modern databases are relational because it provides good balance between data abstraction and performance DBMS Life Cycle ● Planning – What is the goal? What constraints exist? ● Analysis – Audit user requirements ● Systems Design ● Implementation ● Maintenance