CS 47/147 Advanced Object-Oriented Programming - Caltech

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Book Example: File System!FS<strong>Object</strong>Root1Cur≤1contentsFile*entries*DirEntry+name!Name!Dir?*parent (~children)• Two more subsets:– There is exactly one Root Dir,which never changes.– At any time, there may or maynot be a Current Dir.• Root and Cur subsets of Dir.– With exactly one and at mostone member, respectively.– Neither contains all of Dir(open arrowheads)– Root is fixed (double lines).18
Additional Constraints• Diagram does not capture all important characteristics of sets and relations.• Must be accompanied by collection of other constraints.• State each constraint in English and in formal logic.Examples:• A directory’s parent is a directory that contains an entry for it.For d : Dir, d.parent = {d’:Dir | ∃ e in d’.entries with e.contents = d}This completely defines parent in terms of other relations, making it aderived relation.Note: this means that there is at most one entry referring to any directory.• No two entries of any directory have the same name.For all d:Dir, e1,e2:DirEntry, if e1 in d.entries && e2 in d.entries &&e1.name = e2.name, then e1 = e2.19
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 16 and 17: Book Example: File System• A dire
Page 21 and 22: Operations• As for a data abstrac

CS 47/147 Advanced Object-Oriented Programming - Caltech

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