Data Flow Diagram Tutorial
Summary
TLDR本视频讲解了数据流图的基本概念,特别是上下文图(Context Diagram)和图0(Diagram 0)的创建。上下文图是数据流图的起点,展示了系统与外部实体之间的数据流动。图0是对上下文图的展开,详细描述了系统中的最多九个过程,包括实体、数据存储和数据流。通过图书馆借阅系统的例子,视频展示了如何记录借阅者信息、书籍信息、罚款以及借还书的流程,并如何生成月度报告和借阅者交易报告。
Takeaways
- 📈 数据流图(DFD)是一种用于表示信息系统中数据流动的图形化工具。
- 🎯 上下文图(Context Diagram)是数据流图的起点,展示了系统与外部实体之间的数据交换。
- 🔍 上下文图中通常只包含一个过程,该过程代表整个系统,并标明系统名称。
- 📊 上下文图中至少应包含一个输入和一个输出,表示系统的数据来源和去向。
- 💡 绘制上下文图后,接下来的步骤是将其细化为0级图(Diagram 0),即上下文图的爆炸图。
- 🔎 0级图中的流程数量应与上下文图中的流程数量相等,以保持一致性。
- 🌳 0级图可以进一步细化为1级图和2级图等子图,每个子图都是对更具体过程的细化。
- 📋 在0级图中,应包括所有主要数据存储和外部实体,并且每个过程都有编号。
- 🔄 数据流不应重叠,以便于识别每个流程或数据存储所经过的路径。
- 📝 例如,图书馆借阅系统上下文图包括借阅者信息、图书信息、罚款信息以及借阅和归还流程。
- 📊 报告生成是系统功能的一部分,如月度报告和借阅者交易报告,这些报告展示了系统的数据输出能力。
Q & A
什么是数据流图?
-数据流图是一种图形化表示法,用于展示信息系统中数据的流动、数据的输入和输出以及数据的处理过程。
上下文中的“零级图”是指什么?
-零级图,也称为上下文图,是数据流图创建过程中的第一个图,它展示了系统与外部实体之间的数据流动。
在创建数据流图时,为什么首先需要绘制上下文图?
-上下文图是数据流图的基础,它定义了系统与外部实体之间的关系,为后续更详细的数据流图(如零级图和一级图)的创建提供了框架。
在上下文图中,最多可以有多少个过程?
-在上下文图中,最多可以有九个过程,以保持图表的简单性,并能够从这些过程中创建子图。
如何确保数据流图中的数据流不重叠?
-为了确保数据流图中的数据流不重叠,应避免箭头交叉,并清晰地标识每个过程或数据存储所经过的流程,以便于理解和识别。
在数据流图中,如何处理实体和数据存储的重复?
-在数据流图中,可以复制实体和数据存储,但不允许复制过程。所有符号应相互连接,形成一个连贯的图表。
在借阅系统上下文图中,有哪些主要的外部实体?
-在借阅系统上下文图中,主要的外部实体包括借阅者、图书馆工作人员和罚款。
借阅系统中,如何记录新的借阅者信息?
-当新的借阅者想要借阅时,他们的姓名、地址和课程信息将被记录在系统中,并存储在借阅者表中。每个新的借阅者将获得一个基于表中最后一个借阅者ID加一的新的借阅者ID。
借阅系统中,如何处理借阅和归还书籍的过程?
-借阅者请求借阅书籍后,图书馆工作人员将进行确认。确认后,系统将生成借条并交给借阅者。归还书籍时,如果存在逾期,可能需要支付罚款,系统将生成收据并交给借阅者。
借阅系统需要生成哪两种报告?
-借阅系统需要生成月度报告和借阅者交易报告。月度报告显示每月借阅的书籍、书籍标题和借阅次数。借阅者交易报告显示特定借阅者的个人信息、借阅日期、归还日期和借阅的书籍。
在数据流图中,如何表示数据存储?
-在数据流图中,数据存储通常用矩形表示,并通过箭头与相关的过程或实体连接,以展示数据的流入和流出。
Outlines
📊 数据流图与上下文图概述
本段落介绍了数据流图的概念,特别是上下文图(Context Diagram)和图0(Diagram 0)。上下文图是数据流图的基础,通常只包含一个过程,即系统,并标识出与系统交互的实体。图0是创建数据流图的起点,当它被展开时,称为级别0或图0。在图0中,数据流的来源和去向应该保持一致,例如x、y、z三个实体与系统之间的数据流。图0中最多包含9个过程,以保持简单性,并且可以基于图0中的不同过程创建子图。所有主要数据存储和外部实体都包含在图0中。
📚 图书借阅系统实例分析
这一段通过图书借阅系统的例子,详细解释了如何记录借阅者信息、书籍信息、罚款以及借阅和归还书籍的过程。当借阅者首次借书时,其姓名、地址和课程信息会被记录。书籍信息如标题、作者、版权和出版社也会被存储。罚款信息特别是对于逾期归还的书籍会被记录。系统还能够生成月度报告和借阅者交易报告,显示借阅者的借阅记录和书籍的借阅次数。
📈 报告生成与数据流图的构建
最后一段讨论了如何生成月度报告和借阅者交易报告,以及如何通过实体关系图(ERD)创建数据流图。月度报告应显示书籍的借阅日期、标题和借阅次数。借阅者交易报告则显示特定借阅者的详细信息,包括借阅日期、归还日期和借阅的书籍。在构建数据流图时,应避免箭头重叠,并确保所有符号相互连接,以清晰展示数据流和过程。
Mindmap
Keywords
💡数据流图
💡上下文图
💡系统
💡实体
💡输入输出
💡数据存储
💡过程
💡层级图
💡借阅信息
💡报告
💡罚款
Highlights
讨论了数据流图、上下文图以及特定的图0。
上下文图是创建数据流图时的第一个图。
在上下文图中,只使用一个过程,并将其命名为系统名称。
上下文图中至少应有一个输入和一个输出。
当上下文图被展开时,它被称为级别0或图0。
图0中包含实体、过程和数据存储,尽可能详细。
数据流不应重叠,以便识别过程或数据存储。
图0中最多包含9个过程,以保持简单。
每个过程都被编号,以便确定哪个过程被展开。
图0中包括主要数据存储和所有外部实体。
以图书借阅系统为例,分析了实体关系图和产生的表。
介绍了图书借阅系统的功能,如记录借阅信息、存储图书信息和罚款信息。
展示了如何从实体关系图产生上下文图。
解释了如何记录新借阅者的信息和生成借阅者ID。
说明了图书信息如何被记录和存储在图书表中。
描述了罚款信息的记录和存储过程。
阐述了借阅和归还图书的过程,以及可能的支付和收据生成。
讨论了如何生成月度报告和借阅者交易报告。
强调了在图0中不允许重复过程,并且所有符号应相互连接。
Transcripts
hi today we're going to discuss
data flow diagrams context diagram
and specifically diagram 0.
so context diagram in a context diagram
we're going to use
only one process and inside that process
we're going to name it as the system
name
or whatever will be the name of your
system then
zero we're going also to put
the entities needed so that we're going
to get
the sources and seeks of our data
so there should be at least one input
and there should be
at least one output from our system
so context diagram is the first diagram
to be created when creating data flow
diagrams
when this diagram will be exploded
it will be named as level 0 or diagram
0.
so since it's only an explosion of
context diagram
the number of flows from entity
or to the entity should be equivalent so
in here we have only
x y and z going to and
coming from our entities so in our level
0 or diagram 0
it should be the same
then we have level 1 diagram level one
diagram
is also an explosion of diagram zero
so in here level process two
is what is being exploded so that's why
we have the number such
as two point one two point two two point
three
because this is only the explosion of
process two
then we have level two is the child
diagram of two point two
so again this is just child diagram of
2.2 so that's why
the numbers are 2.21 2.2.2
so on and so forth this level 1
and level 2 as what we call as child
diagrams
so drawing diagram 0 is just the
explosion of the context diagram
so we are only getting detail
of what is context diagram
so it is only up to nine processes so
that our diagram would be simple
no too much processes involved the
maximum number of processes in diagram
zero is nine
since we need to make it simple since we
can make
child diagrams out of different
processes
found in diagram 0. each process is
numbered so that
we can be able to determine which one is
exploded major data stores and all
external entities are included in
diagram 0.
so here is an example of diagram 0.
so it includes entities processes
and data stores as much as possible
data flows should not overlap so that we
can be able to identify
which process or which data store that
flow is
going through so that it would be easier
to understand
so here we have an example of book
borrowing system
so while analysis when the person wants
to borrow for the first time
name address and course will be recorded
book information is also stored in our
book borrowing system such as title
author copyright and publisher a fine
information is stored especially for
books who
are returned over jew book
requests information is recorded when a
borrower wants to borrow a book
book information is recorded when a
borrower will return
a book there will be a possible payment
if the borrower will return the book
beyond the due date
and the system should be able to display
or produce two reports the first one is
monthly report
this report will display the date title
of books borrowed
and the total number of times that
specific book is was borrowed
and the second one is borrowers
transactions report
this report will show the individual
transaction
for each borrower the librarian wants to
identify
what are the books borrowed by a
specific borrower
the time it was borrowed when was it
returned
and what are the books borrowed by that
borrower
so based from those information we have
this
entity relationship diagram and from
this entity relationship diagram we have
produced
this tables
so here we have our context diagram from
those information
so when the borrower wants to borrow for
the first time
information of that person will be
recorded on the
system book information that will be
entered by the librarian will
be it will also be recorded in our
system
a fine is also recorded especially if
the borrower
tend to forget to return the book or the
book was lost when the borrower requests
to borrow a book
the librarian staff will confirm it
first
when confirmed a slip will be given to
the borrower
when the borrower returns a book if
there will be possible payments because
of overdue books
then a receipt will be given to the
borrower
if payments or returns were made the
system should also
produce reports such as monthly reports
this monthly report will display what
are the books that are commonly
borrowed by the borrowers borrower's
transaction report
will display specific information about
a certain borrower what are the book
that the borrower
constantly borrows
so let's start with borrower information
so here we have one process for our
diagram zero
so a borrower information will be
recorded
in our system and it will be stored in
our borrower table
every time that there will be a new
borrower the last borrower id
will be taken from the table plus one
then that will be the borrower id of the
new borrower
so the borrower record will be the
borrower id
the name address and course of the
borrower
then let's proceed with book information
so in book information we have the book
id
find id title copyright author
and publisher so the librarian will
provide the information
then the information will be stored in
our book table
if book id is generated by the system
we need to get the last value stored in
our book id
plus one then that will be the new book
id
of the new book
then let's proceed with fine
so fine we'll need to record find
id name and amount so the fine will be
provided by the librarian
and it will be stored in our it will be
recorded in our system
together with the name and amount it
will be stored in our fine table
let's proceed with borrowing of books
so here the borrower requests the book
it will be confirmed by the librarian
staff
if confirmed a slip will be given to the
borrower
so in this case the borrower will
request a book
the librarian will confirm it
so here the borrower will request a book
it will check if the book is available
in our table
so we have here the book id
the date this can be processed using the
system date
then the confirmation coming from the
librarian together with a due date
then a sleep will be generated by the
system
and will be given to the borrower
then we have returning of books and
payments so when the borrower will
return a book
there might be tendencies of payments
due to overdue books if payments or
returns were made
a receipt will be given to the borrower
so in that case in our diagram 0
return books so we have this our erd
our table from our erd so borrow id
this is taken in our borrower table
so that we will know who borrowed the
book
then in our book id so that we will know
what book is being returned receipt
number
this is generated by the system when
we're going to generate a receipt and
will be given to the
borrower number so that we will know
the connection with the receipt and the
slip
number so that we will know what books
are included in the receipt the date
of the payment and how much was being
paid so they are all saved in re
book returns payment table a receipt
will be generated by the system
and given to the borrower
then we have monthly reports
so in a monthly report it should be able
to display
on the screen or print in a paper the
date
the book was being borrowed the title of
books
being borrowed and how many times
those books were being borrowed so to
get the date
when the book was being borrowed we need
to get it
from book request table because in this
book request table
or borrow all information about
borrowing of books are
recorded here title of books borrowed
this can be found in our book table
number of times borrowed still this can
be found in our
book request table then we have
borrowers transaction report so here
the librarian expects to see in her
or his screen or print in a paper
name address and course of a specific
borrower
together with the date borrowed date
returned
and books borrowed
so in that case that is our process 7.
so here so that we can get the
borrower's information
we need to get the borrower tbl borrower
information
such as name course and if we want to
get what are the
books that are being borrowed so we need
to get
it in the book tip table or book tbl
so that we will know when this book
was being borrowed we need to get those
information from book request
tbl and we want to identify when those
books was
returned we need to get the information
from
book returns payment dbl and when this
is generated it will be given to the
librarian so as you can see
we can have multiple data store
we can also duplicate entities
but we are not allowed to duplicate
processes
again we're not allowed to duplicate
processes
as much as possible avoid overlapping of
arrows just like in this example there
is no overlapping of arrows
since we can duplicate data stores and
entities but then again we are not
allowed to duplicate
processes and you need to make sure you
can be able to produce
one diagram it means all these
symbols are connected with each other
so let's check our context diagram
so in here in our borrower we have one
two
three four going out to our borrower
so let's check if our level zero is also
four so we have 1 2
3 and 4. let's go back
we have two arrows going
out to our system so let's
check so we have one and
two so the our entity borrower will only
accept two
flows and in our library staff
it will send a data and it will not
receive
anything so in our library staff
it will only send and no arrows
coming into our entity
in our librarian there are two
information provided by the librarian
so in our librarian there are only two
information
coming out from our librarian
and our librarian will receive two
reports
and our librarian will receive two
reports
so it means this diagram zero
is an explosion of our context diagram
[Music]
i hope you have learned something today
Browse More Related Video
Compulsory A - Chapter 1.1 - Information System
Context & Data Flow Diagram Request: Amazon
Unreal Engine 5 RPG Tutorial Series - #14: Equipment System
17th Int. gvSIG Conference: Version Control System on gvSIG Desktop
UI Toolkit Runtime Data Binding and Logic
Mastering Concept Visualizations: A Simple Workflow for Creating Effective Visuals
5.0 / 5 (0 votes)