CS 47/147 Advanced Object-Oriented Programming - Caltech

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Book Example: File System• A directory has zero or moreentries.– Each entry has a name.– Each entry refers to a file or adirectory.??contentsFileentries*DirEntry+name!!Dir?*parent (~children)• A new set of objects: DirEntry.– Relation entries from Dir toDirEntry.(Inverse relation doesn’t need a name.)– Directories do not share entries.– Entries do not move betweendirectories (immutable).• Also need set Name.– Relation name from DirEntry toName.• What about contents of a DirEntry?Name16
Book Example: File Systemcontents!File*FSObjectentries*DirEntry+name!!Dir?*parent (~children)• The contents of a DirEntry is either aFile or a Dir.– In other words: e.contents ∈ File ∪ Dir• Union of File and Dir is another set,FSObject.– File and Dir are subsets.– They are disjoint (shared arrow).– Their union is the entire superset (filledarrowhead).– They are static: object belongs to sameone for entire lifetime (double line onleft).• Note constraints:– DirEntrys are immutable.(Neither name nor contents changes.)– A DirEntry refers to exactly 1 FSObject.– Many DirEntrys can refer to sameobject.Name17
Page 2 and 3: CS 3Introduction to Software Engine
Page 4 and 5: Last Time: Requirements Analysis•
Page 6 and 7: From Requirements to Design• Soft
Page 8 and 9: The Object Motto“Ask not first wh
Page 10 and 11: Elements of a Data Model• Diagram
Page 12 and 13: Book Example: File System• Basic
Page 14 and 15: Book Example: File System• Files
Page 18 and 19: Book Example: File System!FSObjectR
Page 21 and 22: Operations• As for a data abstrac

CS 47/147 Advanced Object-Oriented Programming - Caltech

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