What is the difference between set and class?
in [OOP]
|
Prev: Call for Papers: WORLDCOMP'07, Las Vegas, June 25-28, Conferences in Computer Science, Computer Engineering, and Applied Computing
Next: Set and Class
From: DBC User on 15 Apr 2007 13:29 I am interested in learning the difference between set (theory) and a class. For example, if I have a class say Person and it has a specialised class student and say sue is an instance of student. Then as per set theory, Student is a subset of Person and Sue is element of student/Person. I can see how instance and specilisation can be represented in set theory. But I can not find a difference. Could some one help me? Thanks.
From: Dmitry A. Kazakov on 15 Apr 2007 15:58 On 15 Apr 2007 10:29:22 -0700, DBC User wrote: > I am interested in learning the difference between set (theory) and a > class. In programming languages class is a set of types. > For example, if I have a class say Person and it has a specialised > class student and say sue is an instance of student. > > Then as per set theory, Student is a subset of Person and Sue is > element of student/Person. I can see how instance and specilisation > can be represented in set theory. But I can not find a difference. > Could some one help me? The class Person has the class Student as a subset. The type Person is an element of the class Person. The type Student is an element of both the class Person and the class Student. Sue is a value of the type Student. It is not of the type Person, but it can be transparently converted to the type Person. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: H. S. Lahman on 16 Apr 2007 12:02 Responding to User... > I am interested in learning the difference between set (theory) and a > class. > For example, if I have a class say Person and it has a specialised > class student and say sue is an instance of student. > > Then as per set theory, Student is a subset of Person and Sue is > element of student/Person. I can see how instance and specilisation > can be represented in set theory. But I can not find a difference. > Could some one help me? In OOA/D one deals with just class systems. A class is simply a set whose members are objects. The class is unique because it is defined, in turn, by a set of properties that all member objects possess. In addition, an OO generalization in UML is just a Venn Diagram from set theory in tree form. The dots are objects (Sue) and subclasses are subsets (Student) of the root set (Person). The reason a tree form is used in UML is because the subsets are defined in by sets of properties and the tree format is convenient for enumerating the properties. (OO inheritance is just a suite of rules for determining which properties a given dot (object) has by "walking" the subset boundaries.) This rather simple mapping to set theory is why OO generalization is referred to as an is-a relationship. Sue is a Student and Sue is a Person. So an OO generalization object reflects membership in both sets (i.e., the object's properties are a union of the properties of all sets in a direct line of ascent to the root superset). IOW, the object instantiates the entire tree. That contrasts with Data Modeling where each set in the tree can be instantiated independently (and always is in an RDB). ************* There is nothing wrong with me that could not be cured by a capful of Drano. H. S. Lahman hsl(a)pathfindermda.com Pathfinder Solutions http://www.pathfindermda.com blog: http://pathfinderpeople.blogs.com/hslahman "Model-Based Translation: The Next Step in Agile Development". Email info(a)pathfindermda.com for your copy. Pathfinder is hiring: http://www.pathfindermda.com/about_us/careers_pos3.php. (888)OOA-PATH
From: DBC User on 16 Apr 2007 12:08 On Apr 15, 12:53 pm, r...(a)zedat.fu-berlin.de (Stefan Ram) wrote: > "DBC User" <dbcu...(a)gmail.com> writes: > >I am interested in learning the difference > >betweenset(theory) and aclass. > > The meaning of these notions if given by their theory. > > For example, the von Neumann-Bernays-Gödelsettheory > > http://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Bernays%E2%80%93G%C3... > > includes classes as well as sets; classes are entities that > have members but that cannot be members of anything. > > Possibly, this is not the notion ofclassyou wanted to > refer to. > > However, for an elaborate discussion you need to give the > theory or specification each of your notion stems from as a > (reference to a )specific text. > > Usually theories are disjunct, so the notion of aclass > in the abovesettheory can not be the same as the notion > ofclassin the Java language specification. > > For example, a Javaclassmight be »public« or »private«, > while asetor aclassin the abovesettheory does not > have such a property. Now that I understood the set and class, could you please explain me the difference between metaclass and class in set theory?? Thanks.
From: carmen miranda on 18 Apr 2007 02:19
"Dmitry A. Kazakov" <mailbox(a)dmitry-kazakov.de> wrote in message news:1569qxsqfs7s4.53cohdjn7tix.dlg(a)40tude.net... > On 15 Apr 2007 10:29:22 -0700, DBC User wrote: > using different names for the different context does not approach "identity". maybe i am thinking that sets and class is about identity. i had some time ag read a lawbok on these issues. from programming they use a class to be the template for all instances of the class produced. the pooling strategy is an analogy. when a new user signs onto the network, he activates a new instance to use, within the group on the network. he is able to communicate with the network as one of the group. the class issue is known from taxonomy, which is something like genus and species. and libraries use the classification for subject which are referred to by their books. but a student is a person in that he breathes? suppose we say that all people are learning, then who is the student. it is not that far fetched to attach learning to the person. object relationships in object programming are based on replication, not much on identity. the shole computer is based on variations of the bits in a string of digits. Oye como va mi ritmo. Bueno pa' goza, Mulata The only reasonable Engish translation would be "Listen how my rhythm goes. Good to get your grove on, Mulata" with Mulata being a 'lovely' nickname to a dark complected woman, possibly to whom the song was dedicated. ### Downloaded: 22/01/2003 16:37 - PST #----------------------------------PLEASE NOTE----------------------------------# # This file is the author's own work and represents their interpretation of the # # song. You may only use this file for private study, scholarship, or research. # #--------------------------------------------------------------------------- ----# "Oye Como Va" by Santana off of Santana's Greatest Hits as tabbed by Ryan Izzo (CD time in parentheses) h = hammer on p = pull off b = bend r = release bend \ = slide ~ = let ring Intro: e|--------7-8-10--7-------| B|-10--10-----------8h10--| G|------------------------| Repeat 4X D|------------------------| A|------------------------| E|-(0:16)-----------------| Spanish: Oye como va ....me lee mo weirdo peudo sa????? (I'm a white boy) English: Listen to how it goes... (someone help) Solo 1: e|-----------------------------------------------------------------| B|-------8---8-7------------------------8---8-7--10----------------| G|-----9---9------7----5h7-7p5--------9---9------------------------| D|-7---------------------------7--7--------------------------------| A|-----------------------------------------------------------------| E|-(0:57)------------------------(1:01)----------------------------| e|-----------------------------------------------------------------| B|-------8---8-7----------------------8-10--8-7--10 b 13-------| G|-----9---9------7--5h7-7p5--------9------------(slow bend)-------| D|-7-------------------------7---10--------------------------------| A|-----------------------------------------------------------------| E|-(1:05)----------------------(1:08)------------------------------| e|-8-8-5-5-8-5--8--5----5------------8-8-5-5-8-5---5---------------| B|--------------------7-------------------------/7-----------------| G|------------------------5h7-7p5---------------------7b8-5--------| D|--------------------------------7--------------------------------| A|-----------------------------------------------------------------| E|-(1:12)--------------------------(1:16)--------------------------| e|-8-8-5-5-8-5--8--5----5------------8-8-5-5-8-5---5~/12-----------| B|--------------------7--------------------------7-----------------| G|------------------------5h7-5------------------------------------| D|------------------------------7p6--------------------------------| A|-----------------------------------------------------------------| E|-(1:19)--------------------------(1:23)--------------------------| e|-8-5--8-5--8-5--8-5--8-5--8-5--8-5--8-5--------------------------| B|-----------------------------------------------------------------| G|-----------------------------------------5h7---5h7-7p5-----------| D|-------------------------------------------------------7---------| A|-----------------------------------------------------------------| E|-(1:27)----------------------------------------------------------| e|-----------------------------------------------------------------| B|---------5---5-7---------------------5---5-7---------------------| G|-5-555-5---5-----------------5-555-5---5-------------------------| D|-(weird)---------4--5--6--7-------------------4--5--6--7---------| A|-----------------------------------------------------------------| E|-(1:34)----------------------(1:38)------------------------------| e|-----------------------------------------------------------------| B|---------5---5-7-------------------------------------------------| G|-5-555-5---5-----------------------------------------------------| D|------------------4--5--6--7-------------------------------------| A|-----------------------------------------------------------------| E|-(1:42)----------------------------------------------------------| mostly keyboard and other junk here . I am not good with chords so if someone could fill in this blank I would appreciate it. Solo 2: e|--5/12---8-8-5-5-8-5--8--5----5-------------8-8-5-5-8-5----------| B|----------------------------7---------------------------7h10-----| G|--------------------------------5h7-7p5--------------------------| D|----------------------------------------7------------------------| A|-----------------------------------------------------------------| E|-(3:20)-------------------------------------(3:26)---------------| e|-8-8-5-5-8-5--8--5----5------------8-8-5-5-8-5----5~/12----------| B|--------------------7--------------------------/7----------------| G|------------------------5h7-7p5----------------------------------| D|--------------------------------7--------------------------------| A|-----------------------------------------------------------------| E|-(3:29)----------------------------(3:33)------------------------| e|-17b18r17b18r17-12-/14--17---------------------------------------| B|---------------------------15------------------------------------| G|--------------------------------12b14---12-b14---12-b14---12-b14-| D|-----------------------------------------------------------------| A|-----------------------------------------------------------------| E|-(3:37)------------------------(3:40)----------------------------| e|-----------------------------------------------------------------| B|-----------10----------------------------------------------------| G|-12-b14-12----12-------------12-----------------------12/13------| D|-----------------12-10----10-12-10----12/13---12/13---12/13------| A|-----------------------12----------12----------------------------| E|-(3:43)----------------------------------------------------------| e|-----------------------------------------------------------------| B|-----------------------------------------------------------------| G|----------------12-----------------------------------------------| D|-12/13-10----10-12-10---------10/12-12p10-------10-12-12p10-10-10| A|----------12----------12--/12-10/12-12p10-12p10-10-12-12p10-10-10| E|-(3:48)-----------------------(3:51)------12p10------------------| e|-8-5--8-5--8-5--/12-5--8-5-8\5--8-5--88-5--8-5--8-5--8-5-8-5-----| B|-----------------------------------------------------------------| G|-----------------------------------------------------------------| D|-----------------------------------------------------------------| A|-----------------------------------------------------------------| E|-(3:55)----------------------------------------------------------| e|-8p5-8-8p5-8-5-8-5-----------------------------------------------| B|-----------------------------------------------------------------| G|-----------------------------------------------------------------| D|-----------------------------------------------------------------| A|-----------------------------------------------------------------| E|-(4:03)----------------------------------------------------------| I don't see too many Santana tabs so this should help. I would love to hear any corrections, suggestions, or praises. Ryan Izzo Oye Como Va by Santana Okay, for those who can't figure out the lyrics to Oye Como Va by Santana, here they are with an english translation too!! Oye Como Va Hey How's it going Mi ritmo My rythm Bueno pa gosar It is fun to dance Dudar No doubt Oh I forgot to say that it is a wierd english translation. It is like if you tell a joke in spanish and then tell the english translation it is not funny. So the way for it to make sense to those who "No speka spanishio" it would be: Hey how's it going There is no doubt that my rythm is fun to dance. > > > -- > Regards, > Dmitry A. Kazakov > http://www.dmitry-kazakov.de |