A data person understands and deepens the domain model

remarks ： This article is a product of some chapters deleted in my own book , The content involved in this article is not expanded here .  

TOGAF

TOGAF  about

The definition of an architect's responsibility is to understand and pay attention to some key details and interfaces that are actually important but do not become overloaded , Specific include ： Understand and parse requirements , Create useful models , confirm 、 Refine and expand the model , Management structure .

TOGAF  namely  The Open Group Architecture Framework （ Open group architecture framework ）, It is a non-profit organization committed to the formulation and promotion of technical standards  The Open Group  Developed for the development of enterprise architecture （Enterprise Architecture） A set of methods and tools .

Business architect ： Be responsible for the realization of customer demands 、 Focus on business logic 、 Customer implementation of specific business scenarios

application architect ： Understand the business , Comb the model , Design patterns , Interface , Data interaction, etc

system architect ： Server load , reliability , Telescopic , Expand , Database segmentation , Cache application, etc

Derivation of enterprise architecture

An enterprise level architecture often has two kinds of derivation structures , One is top-down 、 The other is bottom-up . For example, one for enterprises or independent  BU  The architecture probability is deduced from the top down , If an architecture in a specific business may be derived from the bottom up .

From the focus of enterprise level attention and  IT  In terms of solutions , There are three stages ：

• First stage ： Enterprises have their own business goals, that is, strategies . Around the business strategy, we need to see what kind of system to support

• The second stage is planning , For business strategy and enterprise information strategy, we need to look at business architecture 、IT  More detailed planning and design of architecture , This stage can be called the analysis stage . In the analysis stage, the role of top-level architect abstracts a structured description of enterprise business strategy or information strategy , Other architect roles will continue to further decompose these structured descriptions , Its main task is the planning of business requirements and processes

• The third stage is design delivery, which can be called  IT  Solution ,  In this process, it is necessary to output the domain model in the analysis stage 、 The enterprise conceptual architecture model is systematized 、 Process design

Domain model

A metaphor ： In the process of automobile production , Its production workers are very familiar with their essential work , These workers are usually only responsible for the design or production of one or several parts  , No matter how many years in the post , These workers can't understand the whole process of a car from a macro perspective, a good car , The first is produced in the brain , This is the original model , The designer will record the idea of the car , Next is the design process . Designers will spend a lot of time on the modification and improvement of the design , It is possible for months to years , Until the perfect state is solved , This state is that the designed model can completely reflect what is thought in the human brain .

Domain is a kind of thing in reality , It cannot be changed into a kind of code through simple keyboard input , It needs domain abstraction . To transform anything in the world, we must first recognize and learn . There is no in-depth accuracy 、 Comprehensive cognition , It is impossible to provide a correct solution that can solve the problem .

Eric Evans（ The founder of Domain Driven Design  Eric Evans）  To tell you ,  The complexity of software system comes from its corresponding field ,  Domain knowledge abstraction and modeling are the basic steps of building complex software systems  . This paragraph is related to many domestic ‘” Design method for database modeling “  Seem out of place . This is not to provoke the right or wrong of these two methods ,  But in reality ,  Design method for database modeling , It hides many details of object-oriented analysis and design .

Whether in enterprise application architecture 、 In the middle stage architecture , Both mentioned domain models ,

Abstract business and reuse in the field

. In recent years, the general domain model design method tends to  Eric Evans  Of “Domain-Driven Design” Also known as  DDD  Design method . This design method takes into account the model of comprehensive analysis and design , The boundary of the system needs to be considered ：

• Help analyze and understand complex business domain issues , Describe the entities involved in the business and their relationships with each other , It's the product of requirements analysis , Related to the problem domain

• It is a powerful tool for requirement analysts to communicate with users , It's the language of communication

• Analyze how to meet the functional requirements of the system , Guide the follow-up system design of the project

therefore  DDD  The design method comprehensively considers the business field 、IT  field .DDD  We are encouraged to consider the domain model as the first step after we are exposed to the requirements , Instead of cutting it into data and behavior , Then use database to realize data , Implement behavior with services , Finally, it leads to the separation of requirements .

A transaction payment and clearing business domain modeling

Transaction business model

Let's first look at a common transaction business model for purchasing travel products online

technological process

• The user sends a transaction request to the business line ;

• The business line sends a payment request to the payment center

• After the payment center receives the business line request , Send a payment request to a third-party payment company or bank

• The user completes the payment according to the prompt

• The third-party payment company or bank notifies the user of the payment center through the interface that the payment is successful

• The payment center informs the business line of the successful payment result

• The business line notifies the merchant that the payment is successful , The merchant issues tickets

remarks ： The process described above is temporarily called the payment domain model of online tickets

Business users ：

• Business users of online travel , Two users involved in the transaction of buying tickets at one time 、 A platform , One is the buyer of air tickets 、 One is the seller of air tickets .

Business scenario （ Non login status ）：

• Users will choose one-way ticket when passing through the ticket search page or selection page 、 Back and forth 、 Special Offer 、 date 、 Flight information , The page will send a search request service to the ticket search , The service will return the price information of the tickets for the past seven days .

• Users choose the reservation information they need , And fill in the information of passengers 、 Contact information 、 Reimbursement information travel orders and send them to the order system of the business line

• The order system will retrieve whether the quantity information of the ticket information provided by the merchant is complete and return it to the order system

• The order system will return the confirmation information to the user

• The user selects debit and credit cards according to the status returned by the order 、 Payment platform

• The user gets the payment return result

This online travel payment domain model can be divided into three parts

Customer domain ： There are mainly users 、 Merchant 、 Navigation Division

The business domain ： There are virtual goods 、 Order 、 Products that provide services to users

Payment domain ： transaction 、 payment 、 Trading anti cheating 、 balance 、 Payment account 、 Cashier 、 gateway 、 Liquidation 、 Settlement 、 Accounting and other fields

The payment domain can be further divided into secondary domains , for example

From the perspective of payment secondary domain model, it is divided into five parts

User domain ： There are mainly   Personal account for payment 、 Pay merchant account

Product domain ： Trading anti cheating 、 Balance payment 、 Cashier 、 Quick payment 、 Pay credit 、 Secured transactions 、 Buying on behalf of 、 Pre licensing 、 card 、 refund

Payment process area ： transaction 、 payment

Fund field  ： Liquidation 、 Settlement 、 Reconciliation

Gateway domain  ： Bank 、 Third party payment 、 route

This secondary domain model can be seen ,  The complete payment domain is still very complex , Next, use the three-level small field model of liquidation to further expand .

Liquidation domain model and simple disassembly

Let's take a look at a business case to understand what is liquidation .

The card of China Merchants Bank is commonly used (ps  This is not advertising ), Suppose I went to a city in the west at some time  , I just ran out of cash and need to withdraw cash ,  There is no outlet of China Merchants Bank in this city , But there is China Construction Bank , So only in CCB  ATM  The machine inserted into the card of China Merchants Bank and withdrew  1000  element . This is inter-bank withdrawal for the teller  1000  element , Was charged  2  A handling charge of yuan .

From the perspective of bank business ：

• CCB  ATM  I read a card from China Merchants Bank , And there is a pen  1000  Yuan cash business . At this time, the system of CCB tells China Merchants through the network ,xxxx  Card users want to withdraw cash  1000  element , Judge if you can give him

• The feedback from merchants said , If the account is enough, you can deduct  1000  element , CCB, please put it on first

• CCB  ATM  Spit out  1000  element

At this time, the teller gets cash , Get the card and contribute to the local  GDP  Go to . At this time, the inter-bank withdrawal in the bank is due to the cash obtained from CCB ,  At this time, there will be a debt relationship between banks , CCB owes China Merchants Bank  1000  element , After the capital liquidation of this business of two banks in a cycle , The business between the withdrawing banks is really over .

Empathy , When buying a ticket, the user chooses to pay until the final bank deduction returns the successful payment , The liquidation process of this process is as follows

Business users ：

• user 、 The merchant is initiating a payment 、 Refund business activities , The payment of funds can be completed without perception

• The fund reconciliation and settlement group can pay more attention to some of its businesses , Instead of paying attention to more liquidation level things , At the same time, it can reduce the workload

• For access to new clearing channels 、 It can lay a good foundation for the separation of borrowing and lending 、 At the same time, reduce the cost of the payment center

• Can successfully complete the payment of funds , At this time, the liquidation is in the capital

Business scenario ：

• The clearing operator obtains the file of recharge and import through manual trigger or timing function

• The clearing front-end machine handshakes the bank communication front-end through the interface , Request file

• The bank returns the file , The liquidation front-end machine saves the file locally , And import the data into the corresponding table

• Perform reconciliation , The system compares the data in the table with the data in the clearing instruction table , And return the reconciliation result

A liquidation life cycle ：

Here is the domain model of liquidation , This model belongs to the three-level domain model

entity model ：

As shown in the figure above , The relationship between the liquidation order and the liquidation document is many to one 、 Check that the processed liquidation order and the processing result of liquidation documents are many to one . The relationship between card type and clearing structure products is many to one 、 The relationship between the type of card account and the products of the clearing institution is many to one , In addition, other relationships are one-to-one .

Unified language ：

Unified language is an important link in the business domain , What is commonly used is  UML （ Unified modeling language ） To describe . For example, there are fiveorsix functions in liquidation , Liquidation document management 、 Liquidation order management 、 Internal service management （ Card management 、 Agreement Management 、 Institutional Management ）、 Communication front 、 Others, etc . Because there are many functions involved , The author only chooses the clearing file processing module to do  UML  describe （ In order to maintain the effect of the pictures in the book , I still use it  keynote  To simulate ）.

There are five functions for clearing document processing , They are the acquisition of the echo file 、 Parsing of the export file 、 Import the echo file 、 Import file reconciliation 、 Check the reconciliation result of the import back file . The author gives the sequence diagram of this business , Reconciliation needs to be triggered after import , There are two triggering methods, namely, manual mode 、 System automatic mode , The sequence diagram shown in the figure below is automatic .

The system trigger can be configured as a scheduled task , In this way, you can turn what you want to do in real time into what you can do asynchronously , The system function of scheduled reservation will be used

Complete a sequence diagram after having a use case diagram ：

• Maintenance personnel or scheduled tasks initiate a meeting task request .

• The clearing file processing will send out what I want through the front-end processor through the standard interface .

• The lead opportunity sends a request document to the financial institution .

• The financial institution will return the request document .

• The lead opportunity saves the file .

• The front-end processor returns the path and parameters of file saving to the clearing file processing module .

• The clearing file processing module will call the response parsing format to import the data file into the database .

• Whether the import result returned by the maintainer or scheduled task is abnormal .

• When ready, initiate a reconciliation request .

• Perform reconciliation 、 Reconcile the imported data with the clearing order data .

• Return reconciliation result information , And further improve the follow-up processing .

Data model :

Select an interface dependency model for the clearing order ,  As a case, only a few fields or attributes are placed .

Then the interface is refined （ detail elision ）

Summary

Why should the author, a data person, understand these contents , Because the topic domain abstract design in the big data construction stage , Public theme abstract design , And the omnipotent panacea of big data construction is constantly in spiral reconstruction , Mastering some methods will produce better results .

Author's brief introduction ：

Pine nuts （ Li Boyuan ）,BI&  Data products  20  An old driver , Floating through several big factories .  Official account number  songzi2016