WEEK 2 IM

• INFORMATION SYSTEM CONCEPTS

  A set of interrelated components that collect, manipulate, and disseminate data and information, and provide feedback to meet an objective
• • Components of Information System1Data

  1. Hardware
  2. Software
  3. Telecommunication
  4. People
  5. Procedures
• • Input: collect and introduce data to system
  • Transaction: a business event, usually entered as input 
• • Data processing: perform calculations on input 
• Output: what is produced by the information system
• Storage: vast amounts of data stored on optical discs
• Data. Stored representations of meaningful objects and events.
• Structured: numbers, text, dates

  Unstructured: images, video, documents
• Information. Data processed to increase knowledge in the person using the data
• Metadata. Data that describes the properties and context of user data.
• Properties to describe

  • Data names
  • Length (or size)
  • Allowable values

  Data context to describe

  • Source of data
  • Ownership 
  • Usage
• Database System. Refers to an organization of components that define and regulate the collection, storage, management and use of data within a database environment. 
• Five major parts: hardware, software, people, procedures and data.
• DATA MODELS

  • A collection of concepts that can be used to describe the structure of a database that provides the necessary means to achieve this abstraction.
• ENTITY

  • Is a person, place, thing, or event about which data will be collected and stored.
• ATTRIBUTE

  •  is a characteristic of an entity.
• RELATIONSHIP

  • describes an association among entities.
• • ONE-TO-MANY RELATIONSHIP
  • one entity instance is associated with many instances of the related entity.
• • MANY-TO-MANY
  • entity is associated with many occurrences of a related entity and one occurrence of the related entity is associated with many occurrences of the first entity. 
• • ONE-TO-ONE
  • one entity instance is associated with only one instance of the related entity.
• 1. High-Level or Conceptual Data Model

  • Provide concepts that are close to the way many users perceive data.
• 1. Representational or Logical Data Model

  • Provide concepts that may be understood by end users but that, are not too far removed from the way data is organized within the computer.
• 1. Low-level  or Physical Data Model

  • Provide concepts that describe the details of how data is stored in the computer.
• GOOD BUSINESS RULE IS:

  • Declarative–what, not how
  • Precise–clear, agreed-upon meaning
  • Atomic–one statement
  • Consistent–internally and externally
  • Expressible–structured, natural language
  • Distinct–non-redundant

  Business-oriented–understood by business people
• • A data modeling technique that creates a graphical representation of the entities, and the relationships between entities, within an information system.
• • Entity

  are the "things" about which we seek information. 

  • is a person, object, place or event for which data is collected.
• • Attributes
  • are the data we collect about the entities. 
• • Relationship
  • provide the structure needed to draw information

          from multiple entities or the link between entities.
• • Key Attribute is the unique, distinguishing characteristic of the entity.
• • Composite Attribute can be divided into smaller subparts, which represent more basic attributes with independent meanings. 
• • Required Attributes is an attribute that must have a value; in other words, it cannot be left empty.
• • Optional Attribute is an attribute that does not require a value; therefore, it can be left empty. 
• • Single-Valued Attributes is an attribute that can have only a single value.
• • Multi-valued Attribute can have more than one value.
• • Derived Attribute -  is an attribute whose value is calculated (derived) from other attributes. 
  • The derived attribute need not be physically stored within the database; instead, it can be derived by using an algorithm. 
• DEGREE OF RELATIONSHIP

  •  is the number of entity types that participate in it.
• 1. Unary Relationship : One entity related to another of the same entity type.
• Binary Relationship : Entities of two different types related to each other.
• 1. Ternary Relationship : Entities of three different types related to each other.
• 1. N’ary Relationship : Entities of three or more different types related to each other.