What is a model?

Excerpt from: Open Source it
1) The model must be an object (class)2) the properties of the model object must be persisted (saved) after it has changed, and then it is: Entity object: Commodity object, Order object 3) when the properties of the model object change, do not persist, IS: Business service object, base service object, helper object: Page Flip object, database connection object, order commodity validation class 4) for simplicity, many projects write business in control, Use the model primarily as an entity object: Access thinking 1 user registration scenarios in which every business within the business can write 1 service objects (classes), at least 1 methods of each business object's change each service object can be stored/taken multiple entity objects create order scene check book item: Can Sell (presence/inventory /promotional time) check the booking order item: The user can Buy (level/can participate in the event/reach the event online) to check the order itself preferential policy, the user is using the correct check the address of the order itself/contact/payment Method/distribution method, etc. correctly create order Total price, and verify: According to the offer/postage/insured /invoice ETC Create Order Processing user's offer//Processing commodity inventory processing user Shopping Cart Payment order scenario//Check whether the order can be paid: order time//check whether the order item can be paid: whether it can be sold (presence/inventory/preferential activity time)//Check the booking item: the user can buy (level/ can participate in activities/reach the event on-line) Create payment parameters Submit Payment Interface Order Payment success Scenario Check callback data authenticity Modify order Status processing Merchandise inventory processing points gift etc 5) 4 Color prototype analysis method partplacething (PPT Green): Basic entities: Goods, people, departments, posts, Location, Fixed asset description (DES Blue): Classification of the underlying entity: Commodity classification, Department type, post level, type of person, location area, item classification role (yellow): role: In a particular business situation, increase the business capability (method) of the underlying entity. Use decorator mode Momentinterval (MI red): Business scenario. such as: generating orders, adding shopping carts, departmental moves, job mobility, employee turnover, product sales, outbound Momentinteval (Midetail red): Entity: Detail records in the business scenario: Order Details, sales details, inbound details, out-of-Library details role There are about four ways to achieve: 1, Use dynamic proxies to dynamically inject behavior into PPT. 2, explicit interface implementation + partial class. 3, the Field Service. 4, the State of the field services, the status of: a PPT instance. 

What is a model