Definitions Flashcards
Explain the following relationship characteristic: Degree
Degree refers to how many entity types are associated by the relationship. •unary (1) •binary (2) •ternary (3)
Explain the following relationship characteristic: Cardinality
Cardinality refers to how many entities of Entity type A can be associated with an entity of Entity type B. •An association is one-to-one (1:1), one to many (1:m) or many to many (m:n).
Explain the following relationship characteristic: participation
Participation refers to mandatory or optional association
What is meant by Versioning in relation to data integrity
•keeping different versions to see the history of changes and verify accurate data at different points in time
•clear trail of who changed what and when
•error recovery if file corrupts
•helps manage change to data in a structured way throughout lifecycle
What is meant by deadlock in relation to data integrity
Deadlock refers to a specific situation where two or more transactions are waiting on each other to release locks on resources, and none of the transactions can proceed. This results in a standstill where no transaction can move forward, effectively halting progress and potentially compromising data integrity if not properly handled.
Occur in environments where transaction currency managed through lock mechanism. Locks held by other transactions. Circular dependency means transactions cannot continue. Intervention required to resolve deadlock and restore normal operations.
What is meant by transaction log in relation to data integrity
Transaction log is a critical component in database systems that ensure data integrity by recording all changes made to the data. It serves as a detailed history of all transactions that have been applied to the database. If a system failure occurs, the transaction log can be used to recover database to a consistent state by replaying transactions from the log or rolling back incomplete transactions. This process ensures that the database remains accurate and reliable even after interruptions.
With regard to ERD’s, a relationship type that defines the association between entities. Explain attributes.
Attributes are the information we want about each entity. Eg attributes of the entity type CUSTOMER may be customer name, customer address, telephone number, contact name
With regard to ERD’s, a relationship type that defines the association between entities. Explain participation constraints.
Participation constraints specify whether the existence of an entity depends on its being related to another entity by a relationship.
Two types of constraints:
Total (mandatory) - every instance of the entity must be involved to at least one relationship instance
Partial (optional) - some instances of the entity may not be involved in an relationship instance
What is an entity?
An entity is something in the real world about which we want to store data.
Entity type…
An entity type defines a set of entities that have the same attributes or properties
What is a relationship
A relationship defines the associations between entities
Name the properties an attribute may have
Single valued or multi valued
Derived
Null
Key attribute
What is a composite attribute?
A composite attribute is one which can be divided into simple attributes - each with its own meaning
Eg address can be spilt into street name, town, city, country
What is a simple attribute ?
Cannot be sure her sub-divided
Eg surname
What are derived attributes
Value of some attributes can be derived from other attributes and so do not need to be stored in a database.
Eg persons age derived from DOB
What is a null attribute?
Not all attributes have value for each entity
Eg employee entity type gave an attribute car reg number but not all employees have a car
What are key attributes ?
Primary keys is an attribute or set of attributes that uniquely identifies each entity. This key must:
- not change value
- always have a value for each entity
- no attribute uniquely identifies each entity, we add surrogate key
Shown as PK - primary key
What is a data dictionary
A data dictionary is a working tool for programmers and powerful users who must deal directly with the database.
Alphabetical list it tables columns and descriptiosn
What is a foreign key?
A foreign key (fk) is an attribute in a table which is the primary key for another table
What is normalisation?
Normalisation is a set of steps to ensure a good database design
Ie well structured tables where all attributes are functional and dependant on the PK
What is the purpose of normalisation?
The purpose of normalisation is to
- avoid redundancy by storing each ‘fact’ within the database only once
- to put data into a form that conforms to relational principles
- to put data into a form that is more able to accommodate change
- to avoid certain updating anomalies
- to facilitate enforcement of data constraints
What are the three steps to producing a well structured relations
1) remove repeating groups (1NF)
2) remove partial dependencies (2NF)
3) remove transitive dependencies (3NF)
** once in third normal form (3NF) tables can be described as well structured
What is the first normal form?
The first normal form (1NF)
- a table in the first normal form is when it contains no repeating groups (each field contains one value)
- a repeating group is a group of attributes which have more than one value for each instance of the primary key
- first normal form achieved by resolving multi- valued and composite attributes and resolving to many relationships
What is the second normal form?
The second normal form (2NF)
- a table in the second normal form when it is 1NF plus all partial dependencies have been removed I.e. no attribute is dependant on only part of the primary key
- attributes partially dependant on the primary key moved to new table
- primary key if new table is part of the original key which attribute was dependant on
- original key becomes foreign key
What is the third normal form ?
The third normal form (3NF)
- a table is in the third normal form when it is in 2NF plus it contains no transitive dependencies. This ensures each attribute is dependant on a primary key only
- a transitive dependency is an attribute which is functionally dependent on some other attribute that is not the primary key.
- to remove transitive dependency, we move the attributes to a new table.
- the pk will be the attributes they were dependent on in the original table. Which becomes the foreign key.
What is systems analysis about?
Systems analysis is about understanding the business and improving efficiency of its processes not just designing a technical solution
What are the processes to going about analysis?
Understanding the business
•business strategy (documented)
• industry understanding
• senior management interviews and workshops
Process efficiencies
• procedure documents
• existing systems
• operational staff interviews and workshops
• process mapping
What are approaches to solution design?
Greenfield top-down
• blank sheet
• brainstorming
• bare minimum
• ideal process
Model driven
• best practise
• enablers
• packages
Process re-design bottom-up
• process mapping
•process validation
• NVA activities
• change inputs
Test, reiterate, move on
Has the problems been solved
Critical Success Factors (CFS) - the things that an org must do well in order to succeed
Brainstorming
Bare minimum to provide necessary outputs
Process mapping
Storyboarding
What are critical success factors
Limited number of characteristics, conditions, or variables that have direct impact on effectiveness, efficiency, and viability of an org program or project
Ensures successful outcome of org or project
A quality improvement tool
Indicates that measure how well an org/ program/ project accomplish strategic plan and objectives
To be effective, CSF must;
- be vital to org success
- benefit whole company/ dep
- high level goal
- link to strategy
Where do CFS come from?
Could be related to…
- industry
- competitive strategy
- environmental factors
- temporary problems
How do we achieve CSF?
Monitor performance
Average stock life
Number of stock sold out
Amount out of date stock
Shelf space for each stock item
Stores space for each stock item
What are two CSF example
Restaurant
- customer satisfaction
- market share
- employee turnover
- food quality
- staff satisfaction
Church
- weekly attendance
- volunteers
- weekly contributions
- visitors
- customer satisfaction
CFS project management
- Agree on project goals
- develop clearly defined plans and responsibilities
- manage project scope efficiently
- cultivate constant effective communication
- management support
- complete project goals in timeframe
- test and update goals at intervals
What is brainstorming
Generally performed in groups
Combined relaxed, informal approach to problem solving with lateral thinking
- outside the box thinking
- identify current spot and end goal->what are the things needed to fill the gap
- SWOT opens up to new ideas may not have seen
What is process mapping
Process mapping is a graphic representation of a process showing sequences of tasks using a standard set of symbols
- used to draw step by step diagrams how work is processed
- used in business to capture current state of business operations in preparations for improvement
- helpful to increase productivity among staff
- helps to breakdown complex processes improving process flows
Process of process mapping
To create a process map you need to identify key process objective and main activity steps
Process or action step represented by rectangle
Decision branching due to result, diamond with 2 arrows going either way
Direction of activity represented by arrow
What is contained within a process map?
1) identify start and end of process
2) identify all tasks/ activities
3) identify decisions
4) determine sequence of steps
Why should we use business processes?
- document and analyse current business processes
- start people to think about processes in a way that enables improvement
- ensure that value adding activities and outputs are not lost in redesign
Describe a swim lane diagram
- lanes used to display info and connecting it with the each other
- individual lanes in chart and each lane assigned to a representative that is responsible for that lane and represents either a department project or part of company
- gives clean overview or details about system where more phases are included
- used to train and educate staff about strategies or policies of a company
- allows to find weak points in system where its each to make mistakes or hack
- helps with strategy making and plans
- also called cross functional diagram
What is a storyboard?
A storyboard is a graphical illustration of a high level process
Tells a story or gives instructions quickly or visually
Often used as a pitching tool to high level executives who have short attention spans
Used as part of creative process such as advertising
Should include key words
What are metrics ?
- vital part of any business analysis exercise
- data collected on how often the process cycle reoccurs and how long cycle should take
- provides vital data for system scale, performance and system response time
- key insights into the process
What are the processing areas of a typical system ?
How is processing divided by C/ S
- Manipulating the data by accessing the correct file and retrieving the correct data
- presenting the information in the screen for the user
- determining what data is required
- validating the information entered by user
- applying information changes
c/s - client servers
What is single tier architecture?
Time of huge mainframes
All processing in single computer
Al resources attached to same computer
Access via terminal
What are two tier and three tier architectures ?
Two teirr
- client
- server
Three+ tier
- client
- middleware - web server application
- server
What is a client ? (Client server architecture csa)
Anything that connects to a network
What is a server?
A server is a device that provides a service to another computer program and its users
- it files storage
- printing (to shared printer)
- lisence services
- fax
- mail
Backups - shared database -> requests sent to server using SQL data is extracted and returned to client
Requires
- high power CPU
- fraud intolerant
- network operating systems
Sometime called back end
What is a client server ?
W computer model that distributes functions in a system between servers and clients where servers provide serves and clients use services
Ie a server that everyone connects to
What are the key principles of a client server
- hardware independence
- software independence (operating systems, network operating systems and applications )
- access to all network services
- process distribution with (separation of client and server, local utilisation of resources by client or server, fully integrated with ability to swap server processes)
- standard network for talking between applications
What are the allocation logics in C/S systems
Presentation logic
- input key board / mouse
- output monitor/ printer
These are GUI interfaces
Processing logic
- I/ O processing
- business rules
- data management
These are procedures, functions and programs
Storage logic
- data storage / retrieval
These are DMBS activities
What is file server architecture ?
All processing done on a of that requested data
- clients known as fat or thick clients
Entire files transferred from server to client for processing
Problems
- huge amount of data transfer on network
- each client must contain full DBMS
this is a heavy resource demand on clients and client DMBS must recognise shared love integrity checks ect
Discuss two tier C/S approach
Client responsible for
- I/O processing logic
- some business rules logic
Server performs all data storage access processing -> database is only on server
Advantages
- clients do not have to be as powerful
- greatly reduces data traffic
- improves data integrity since processed centrally
- stored procedures some business rules done on server
What are the three layers of a three tier architecture?
Three layers
Client
Application server
Database server
Thin client - pc just for user interface and a p little application processing limited it no data storage -> sometimes no hard drive
What are the advantages and disadvantages of three tier architecture
Advantages
Scaleability
Technological felxibility
Long term cost reduction
Better match if systems business needs
Improved customer service
Competitive advantage
Reduced risk
Disadvantages
High short term cost
Tools and training
Experience
Incompatible standards
Lack of compatible user end tools
What is middleware ?
Software used to bridge gap between applications and databases and sits between operating systems and applications
Software allows application to interoperate with other software
Provides method of communication and data management between apps that wouldn’t be able to exchange data
No need for user to understand internal processing
The glue that holds the client / server apps together
Examples of database middleware
open database connectivity (OBDC)
Java database connectivity (JDC)
