conceptual-model | 易学教程

Concept of comparing numbers with tolerance

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问题 I wanted to ask if there is a better way to compare numbers with a tolerance than mine. Edit: It seems I was way to vague with my explanation. added some information into the text. This is concept only until now. I have not programmed any of it yet. I want to compare around 6000 numbers with each other. The measured numbers [A] are slightly off than the numbers of [B]. [A] are the calculated molar masses of molecules (polymers to be specific). [B] are the measured molar masses of the

Concept of comparing numbers with tolerance

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Fan trap and chasm trap - Database

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问题 Can anyone tell me what is chasm trap? Perhaps fan trap too as I'm not too clear. Also, please provide easy to understand examples (via Chen notations). My understanding thus far: I understand that Fan trap is M:1:1:M, which suggests the paths between entities is ambiguous. I understand that. For example, if M represents Student and the other M represents School then it'll be ambiguous because we don't know which student studies at which school (that's what I understood so far). However, I

Using “Include foreign key column in the model” option in EF wizard

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问题 Do you mostly use this option (the default is checked) or do you uncheck it? I found out that when I have both FK column and navigation property on my entities it results in problems with mapping tools - they might bind one or the other but almost never both. If we were to follow the guidelines of conceptual models strictly I think those columns should never make it to properties, should they? Hopefully many of you reply so we can get a better representation of what developers choose more

Entity Relationship Model for Student / Advisor application

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问题 I'm building a web application concerns a student and an adviser. The student will select his independent study and an adviser will supervise it. I am struggling to find the correct relationship for my program. Basically the actors in my application are. a Student can select 1 independent study. a Student can only have 1 Adviser. an Adviser can supervise multiple Students. a coordinator can be an adviser also My attempt to make ERD for my application. Student - > Adviser (1 to many)

Using “Include foreign key column in the model” option in EF wizard

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Do you mostly use this option (the default is checked) or do you uncheck it? I found out that when I have both FK column and navigation property on my entities it results in problems with mapping tools - they might bind one or the other but almost never both. If we were to follow the guidelines of conceptual models strictly I think those columns should never make it to properties, should they? Hopefully many of you reply so we can get a better representation of what developers choose more often. If we were to follow the guidelines of conceptual models strictly I think those columns should