Muddiest Point - Week of September 24, 2012

I am confused about what a key/primary key/foreign key is, and what the role they play in a database is.

Reading Notes - Week of September 24, 2012

Wikipedia Entry: “Database”

• A database is an organized collection of data
• The data is usually organized to model relevant aspects of reality in a way that supports processes requiring the information
• Term database system implies that the data is managed to some level of quality
• Well-known database management systems include Oracle, IBM DB2, Microsoft SQL, Server, Microsoft Access, PostreSQL, MySQL, and SQLite
• A way to classify databases involves the type of their contents (ex. Bibliographic, document-text) or by their application area (ex. Accounting, banking)
• Relational model – applications should search for data by content, rather than by following links
• Relational database systems are the current dominant system
• General purpose DBMS aim to satisfy as many applications as possible, but they are not always the best solution
• Major database usage requirements
• Functional requirements
• Defining the structure of the data
• Manipulating the data
• Protecting the data
• Describing processes that use the data
• Operational requirements
• Availability
• Performance
• Isolation between users
• Recovery from failure and disaster
• Backup and restore
• Data independence
• Current data models
• Relational model
• Entity-relationship model
•  Object model
• object-relational model
• XML as a database model
• Database design is done before building it to meet the needs of end-users within a given application tat the database is intended to support

Wikipedia Entry: “Entity-Relationship Model”

• The entity-relationship model is an abstract way to describe a database
• Starts in a relational database with data stored in tables
• Data in the tables point to data in other tables
• Two levels of the ER Model
• Conceptual data model
• Logical data model
• An entity can be defined as a thing which is recognized as being capable of an independent existence and which can be uniquely identified

Phlonx, " Database Normalization Process"

Database normalization relies on three forms; no repetition of elements or groups of elements, no partial dependencies on a concatenated key, and no dependencies on non-key attributes.

Muddiest Point - Week of September 17, 2012

I have heard that DNG is one of the best formats to use for photos since it results in almost no data loss. If this is true, why is the TIFF format still preferred for archival use?

Reading Notes - Week of September 17, 2012

"Data Compression" from Wikipedia

• Data compression involves encoding information using fewer bits that the original representation
• Two types of compression
• Lossless
• Reduces bits by identifying and eliminating statistical redundancy
• Lossy
• Reduces bits by identifying marginally important information and removing it
• Formally known as source-coding
• Helps reduce resource usage (ex. Data storage space, transmission capacity)
• Theoretical background
• Lossless – Information Theory
• Lossy – rate-distortion theory

"Data Compression Basics"

• Part 1: Lossless Data Compression
• Fundamental idea behind data compression is to take a given representation of information and replace it with a different representation that takes up less space, from which the original data can later be recovered
• If the recovered information is guaranteed to be exactly identical to the original, then the compression method is described as “lossless”
• A simple lossless compression algorithm is “run-length encoding” (RLE)
• Replaces long runs of characters with a single character and the length of the run
• Lempel-Ziv compressor family
• Entropy coding
• Assigns codes to blocks of data in a way that the length of the code is inversely proportional to the statistical probability of the block of data
• Prediction and error coding
• Part 2: Lossy Compression of Stills and Audio
• important to distinguish data from information
• fundamental idea behind lossy compression is preserving meaning rather than preserving data
• by allowing for some deviation from the source data when encoding patterns, lossy compression greatly reduces the amount of data required to describe the “meaning” of the source media
• lossy compression is ideally applied to information that is meant to be interpreted by a reasonably sophisticated “meaning processor”(human, image recognition software, etc.) that looks at a representation or rendering of the data rather than the data itself

Edward A. Galloway. “Imaging Pittsburgh: Creating a Shared Gateway to Digital Image Collections of the Pittsburgh Region.”

• The main focus of the project was to create a single Web gateway for the public to access thousands of visual images held in the collections of the Pitt Archives Service Center, CMOA, and the Historical Society of Western PA
• The content partners were responsible for selections of collections/images, describing/cataloging images, digitization, and delivering images/metadata to DRL
• DRL was responsible for providing access to the image collections via DLXS middleware
• Characteristics of the Web gateway
• Conduct keyword searches across all image collections
• Browse images
• Read about the collections and their contents
• Explore images by time/place/theme
• Order image reproductions
• Communication challenges
• Selection challenges
• Metadata challenges
• Project-wide vs local needs
• Workflow challenges
• Website development challenges

I was not able to access "Youtube and Libraries: It Could be a Beautiful Relationship" by Paula L. Webb.