Question

这是我的约会数据库的Z架构。

|--AppointmentDB----------------
|attendees : P Person /** those involved in the appointment **/
|
|/** a new TYPE object to store attendees, schedule and purpose **/
|appointments : P APPOINTMENT
|hasAppointment : Person <-> APPOINTMENT
|schedule : APPOINTMENT -> DateTime
|purpose : APPOINTMENT -> Report 
|
|/** a forward relation compositions to relate attendees with purpose and schedule **/
|attendeePurpose : hasAppointment;purpose 
|attendeeSchedule : hasAppointment;schedule 
|-----------------------------
|attendees ⊆ dom(hasAppointment)
|attendees ⊆ dom(attendeePurpose)
|appointments ⊆ ran(hasAppointment)
|-----------------------------

我想创建一个搜索功能，根据attendees的名称查找约会。

我希望搜索功能返回约会对象的所有细节。

我该如何设计？

以下是我的观点：

|--FindAppointment---------------------------------------------------
|ΞAppointmentDB
|attendees? : Person
|appointmentAttendees! : P Person
|appointmentPurpose! : Report
|appointmentSchedule! : DateTime
|-----------------------------
|/** if name of any attendees is given, then it must exist in appointments' domain
|respectively before this function can run**/
|attendees? ∈ dom(attendees)
|
|/** return the set of attendees of the same APPOINTMENT using attendees? as input **/
|appointmentAttendees! = hasAppointment~(|{attendees?}|)
|
|/** Get the image of both forward relational compositions according to set of 
|attendees?**/
|appointmentPurpose! =  attendeePurpose(|{attendees?}|)
|appointmentSchedule! = attendeeSchedule(|{attendees?}|)
|----------------------------------------------------------------------

Answer 1

您是否键入了检查规格？您的声明subject? : P Person声明subject?是一组人，但subject? : dom(attendees)表示subject?是一个人。

如果你想要一个人或一个人，你可以在函数式编程语言中引入类似于Maybe monad的数据类型（或其他编程语言中的null值）：
```
MaybePerson ::= NoPerson | JustPerson <<Person>>
```
然后你可以声明像
这样的输入
```
subject? : MaybePerson
```
然后我建议限制一个输入的可能解决方案
```
subject? : ran(JustPerson) => schedule! : schedule(|{ JustPerson~ subject? }|)
```
如果subject?是一组人，您可以通过以下方式实现相同目标：
```
subject? /= {} => schedule! : schedule(|subject?|)
```

然后就其他可能的输入做同样的事情。您还可以添加一个条件，而不是两个条目都应该NoPerson。并非两个输入集都应为空。

如何以Z表示法设计搜索操作，搜索功能至少需要一个细节？

1 个答案: