Wille frågor Flashcards
3 things. Static situation you want to model(Concepts);
It only describes entities, relationships among entities and attributes to entities (also relationships).
The process that you want to model;
In a process, we can have object types like events, activities, processes, and relations among the “nodes” can be “lead to”, loops, conditional branch, etc.
The Goal/General requirements you want to model;
How to achieve a “pass” of the course?
What problems are there that hinder the achievement?
How to overcome these problems?
Is there an opportunity to find a solution?
Why we need conceptual modeling:
The conceptual modelling (design) cannot be automated or helped by automatic tools.
The designers have the full responsibility for the process of understanding and transforming requirements into conceptual schemas.
There are tools for fast prototyping and developing simple databases after the first conceptualization.
The conceptual design is independent from a particular DBMS. This feature generates several advantages:
The conceptual schema can survive a late decision to change the target DBMS.
If the DBMS or application requirements change, the conceptual schema can still be used as a starting point of new design activity.
Different databases, described through their conceptual schemas, can be compared in a homogeneous framework.
The conceptual schema, as a part of the organizational information system, is one of the important documentation results for any further extension, change, enhancement, and maintenance purposes.
What is conceptual modeling?
When a data model describes a set of concepts from a reality, we call it conceptual model.
Quality of conceptual modeling:
Expressiveness. The real world is abundant in its variety and changes. A conceptual model must be able to express various concepts and their properties.
Simplicity. A conceptual model must be simple so that a schema built using that model is easy to understand for the designers and users of the database application.
Minimality. A conceptual model must use a minimal set of conceptual constructs to represent the reality (each concept must distinctly represent a meaning).
Formality. It requires that all concepts of the model have a unique, precise, and well-defined interpretation.
Key concepts of conceptual modeling:
Basic concepts provided by the ER model are entities, relationships, and attributes. Note that we use the terms entity and relationship to denote classes of objects.
Entities. Entities represent classes of real world objects. PERSON, MAN, WOMAN, EMPLOYEE, and CITY are examples of entities for a personal database. Entities are graphically represented by means of rectangles.
Relationships. Relationships represent aggregations of two or more entities. An example of a binary relationship in the personal database is IS_BORN_IN, which relates PERSON and CITY of birth. Relationships are graphically represented by means of diamonds.
Attributes. Attributes represent elementary properties of entities or relationships. All the extensional information is carried by attributes. For example, attributes of PERSON are: NAME, PERSON_NUMBER, JOB, HOME_ADDRESS.
Benefits of conceptual modeling
The conceptual design is independent from a particular DBMS. This feature generates several advantages:
The conceptual schema can survive a late decision to change the target DBMS.
If the DBMS or application requirements change, the conceptual schema can still be used as a starting point of new design activity.
Different databases, described through their conceptual schemas, can be compared in a homogeneous framework.
Why do we need conceptual model
Using conceptual models, one can build a description of reality that is easy to understand and interpret.
Workflow (make example of you own) Each process is a work. Describe the work and the sequence of the work
Workflows automate the flow of employee tasks and activities, reducing the time the process taken to complete as well as potential errors caused by human interaction.
You should be aware of what is functional analysis. You need to know this concept wise.
Functional analysis is the modelling of working activities within an enterprise.
A function is simply a portion of the enterprise.
Functional analysis concentrates on understanding how information is used by each function and how it is exchanged among the functions.
Functional analysis is the first step toward the specification and design of application programs that operate on the database.
How to use DFD?
A data flow diagram (DFD) maps out the flow of information for any process or system. They can be used to analyze an existing system or model a new one.
How to use OM?
use it to break down big goals into smaller ones and mark out hinders/problems and opportunity’s.
How to use ER?
Map out relationships between entities and there attributes.
Stakeholders
Stakeholder: an individual, team, or organisation (or classes thereof) with interests in, or concerns relative to, a system
