CC6 - Chapter 2 Flashcards
is the process of discovering, analyzing, and scoping data requirements
, and then representing and communicating these data requirements in a precise form called the data model. Data modeling is a critical component of data management.
Data modeling
is answering the question of “how”
* How the data will be gathered
* How the data will analysed
* How the data requirements will be grouped depending on their subset
* After that processes makakabuo na ng data model by communicating the data requirements.
Data modeling
are critical to effective management of data. They:
Provide a common vocabulary around data
Capture and document explicit knowledge about an organization’s data and systems
Serve as a primary communications tool during projects
Provide the starting point for customization, integration, or even replacement of an application
Data models
Goals and Principles
Confirming and documenting understanding of different perspectives facilitates:
Formalization: A data model documents a concise definition of data structures and relationships
. It enables assessment of how data is affected by implemented business rules, for current as-is states or desired target states.
Scope definition: A data model can help explain the boundaries for data context and implementation
of purchased application packages, projects, initiatives, or existing systems.
Knowledge retention/documentation: A data model can preserve corporate memory
regarding a system or project by capturing knowledge in an explicit form. It serves as documentation for future projects to use as the as-is version.
is most frequently performed in the context of systems development and maintenance efforts, known as the system development lifecycle (SDLC)
.
Data modeling
is a representation of something that exists or a pattern
for something to be made. A model can contain one or more diagrams.
model
describes an organization’s data as the organization understands it
, or as the organization wants it to be. A data model contains a set of symbols with text labels that attempts visually to represent data requirements as communicated to the data modeler, for a specific set of data that can range in size from small, for a project, to large, for an organization.
Data model
: Data used to classify and assign types
to things. For example, customers classified by market categories or business sectors; products classified by color, model, size, etc.; orders classified by whether they are open or closed.
Category information
: Basic profiles of resources needed conduct operational processes such as Product, Customer, Supplier, Facility, Organization, and Account.
Resource information
: Data created while operational processes
are in progress. Examples include Customer Orders, Supplier Invoices, Cash Withdrawal, and Business Meetings.
Business event information
: is often produced through point-of-sale systems
(either in stores or online).
Detail transaction information
- is a thing about which an
organization collects information
. - sometimes referred to as the
nouns of an organization
. - can be thought of as the answer to a fundamental question –
who, what, when, where, why, or how
– or to a combination of these questions.
entity
are the occurrences or values of a particular entity
Entity instances
Entity -/ type, instance
Entity – Jane, Employee
Entity type – Employee
Entity instance – Jane
Entity – Raine, Lecturer
Entity type – Lecturer
Entity instance – Raine
In _________ the term relationship
is often used, _________________ the term navigation path
is often used, and in _____________ terms such as **edge
or link
**are used, for example._______ can also vary based on level of detail. A relationship at the conceptual and logical levels is called a relationship, but a relationship at the physical level may be called by other names, such as constraint or reference, depending on the database technology.
relational schemes
dimensional schemes
NoSQL schemes
Relationship aliases
Relationships between two entities
Cardinality is represented by the symbols that appear on both ends of a relationship line.
Data rules are specified and enforced through cardinality.
* Without cardinality, the most one can say about a relationship is that two entities are connected in some way.
The number of entities
in a relationship is the __________________ of the relationship. The most common are unary, binary, and ternary relationships
‘arity’
relationship involves only one entity
. A one-to-many
recursive relationship describes a hierarchy, whereas a many-to-many
relationship describes a network or graph. In a hierarchy, an entity instance has at most one parent (or higher-level entity). In relational modeling, child entities are on the many side of the relationship, with parent entities on the one side of the relationship. Ina network, an entity instance can have more than one parent.
unary (also known as a recursive or self-referencing)
An arity of two is also known as _____________. A binary relationship, the most common on a traditional data model diagram, involves two entities.
binary
An arity of three, known as ________, is a relationship that includes three entities. An example in fact-based modeling (object-role notation) appears in Figure 35. Here Student can register for a particular Course in a given Semester.
ternary
- is used in
physical and sometimes logical relational data
modelling schemes to represent a relationship. - may be
created implicitly when a relationship is defined between two entities
, depending on the database technology or data modeling tool, and whether the two entities involved have mutual dependencies.
foreign key
(also called a key) is a set of one or more attributes that uniquely defines an instance of an entity
. This section defines types of keys by construction
(simple, compound, composite, surrogate)
and function
(candidate, primary, alternate).
identifier
is one attribute that uniquely identifies an entity instance.
* Ex. Universal Product Codes (UPCs) and Vehicle Identification Numbers(VINs).
simple key
- is also an example of a
simple key
. - is a
unique identifier for a table
. Often a counter and always system-generated without intelligence, a surrogate key is an integer whose meaning is unrelated to its face value.
surrogate key