Re: [Zope-dev] _p_deactivate() and _v_ variables?
On Thursday 09 October 2003 14:01, Florent Guillaume wrote: > > I agree with this. How do we go about find code that uses the assumption > > that _v_ stuff won't change unless it's at a transaction boundary? > > Note that we had a problem related to this with a client recently: In > CMF, skin data is stored in portal._v_skindata, and is actually needed > for the whole request, but in some ZEO setting this go cleared by a > get_transaction().commit(1) which was unexpected and led to breakage > because in that batch treatment we used some skin methods too... Something after the subtransaction commit must be tickling the cache garbage collector. Thats generally what subtransactions are used for. A while ago there was a discussion on zodb-dev about _v_-like attributes that would be automatically cleared at the end of a transaction. Do we need something similar that guarantees it will _not_ be cleared until the end of the transaction? -- Toby Dickenson ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] relations in objects
I'm sorry for my ignorant use of the terms relation and relationship. I'll try to use the terms more appropriately in the future. I think I understand where I've become confused. In many of the persistance mechanisms I've looked at references to other objects were handled specially, and had rules associated with them. I think I understand now that it is mearly just a design problem, nothing having to do with zope. When creating objects I will need to pass the reference to the other object, or have a manager for the relationship. I had assumed that objects were somehow self aware in some way of the zope environment, and therefore coule access it. I appologize for any time I might have wasted. The solution is simpler than I had thought. Jason Corbett --- Leonardo Rochael Almeida <[EMAIL PROTECTED]> wrote: > On Fri, 2003-10-10 at 00:46, Jason Corbett wrote: > > Thanks for your reply. I've actually been > thinking in > > an object oriented form for a while. I've looked > at > > implimenting this project in Java using either > > prevailance or a object persistence model that > mapped > > to a RDBMS. I like the idea of zope, so maybe I > > should clarify my question: > > > > How does an object in zope know where it sits in > the > > hirearchy, and how does it reach other objects. > > That's what I'm really looking for, I can probably > > code the rest of the parts. > > In my experience, you should put an object inside > another if and only if > they have an explicit containment relationship, e.g. > a car has 4 tires > and a steering wheel. The steering wheel can belong > to (at most) one car > at any moment in time, so it would make sense to put > the steering wheel > object inside the car object. The same is not true > of, for instance, > students and school classes. In this case you either > store a reference > to the student in the school class (eg a student id > in a "lines" or > "tokens" property) or you create an object to > represent the > class-student relationship (for example an > enrollment) and store it > somewhere. > > Tip: always use methods that return the objects you > need, for instance > aSchoolClass.students() this way you can more easily > change the storage > of the relationship information when you change your > mind. And you will > change your mind a lot of times. > > Tip2: a lot of times you'll implement the above > mentioned methods as > catalog queries, like: what objects in the other > side of the > relationship reference me? > > Tip3: look mxmRelations > > Cheers, Leo > > PS: just because this is a pet peeve of mine, I'll > explain that a > "relation" and a "relationship" are two very > different things. > "Relation" is the mathematical term for a table, a > set of distinct > elements (rows) with the same kinds of attributes > (columns). You can > think of a relation (table) of cars, or a relation > (table) of students. > Relational databases get their names because they > store relations and > allow you to do some relational algebra with > (usually) SQL. > > A relationship, on the other hand, is a link, or > association, between > elements. > > RDBs allow you to model relationships relatively > easily thru either > relational operations: > > SELECT * from cars, steering_wheels > WHERE steering_wheels.carId = car.carId AND > steering_wheels.wheelType = "sport" > > or by storing relationship information in relations > (sometimes known as > "link relations" or "link tables"): > > SELECT * from enrollments, classes, students > WHERE classes.classId = enrollments.classId > AND > enrollments.studentId = > students.studentId AND > students.studentName = "Jason Corbett" > > But RDBs themselves have absolutely no concept of > "relationships". > > So, next time you read the word "relation", think > "table" :-) > __ Do you Yahoo!? The New Yahoo! Shopping - with improved product search http://shopping.yahoo.com ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] relations in objects
On Fri, 2003-10-10 at 00:46, Jason Corbett wrote: > Thanks for your reply. I've actually been thinking in > an object oriented form for a while. I've looked at > implimenting this project in Java using either > prevailance or a object persistence model that mapped > to a RDBMS. I like the idea of zope, so maybe I > should clarify my question: > > How does an object in zope know where it sits in the > hirearchy, and how does it reach other objects. > That's what I'm really looking for, I can probably > code the rest of the parts. In my experience, you should put an object inside another if and only if they have an explicit containment relationship, e.g. a car has 4 tires and a steering wheel. The steering wheel can belong to (at most) one car at any moment in time, so it would make sense to put the steering wheel object inside the car object. The same is not true of, for instance, students and school classes. In this case you either store a reference to the student in the school class (eg a student id in a "lines" or "tokens" property) or you create an object to represent the class-student relationship (for example an enrollment) and store it somewhere. Tip: always use methods that return the objects you need, for instance aSchoolClass.students() this way you can more easily change the storage of the relationship information when you change your mind. And you will change your mind a lot of times. Tip2: a lot of times you'll implement the above mentioned methods as catalog queries, like: what objects in the other side of the relationship reference me? Tip3: look mxmRelations Cheers, Leo PS: just because this is a pet peeve of mine, I'll explain that a "relation" and a "relationship" are two very different things. "Relation" is the mathematical term for a table, a set of distinct elements (rows) with the same kinds of attributes (columns). You can think of a relation (table) of cars, or a relation (table) of students. Relational databases get their names because they store relations and allow you to do some relational algebra with (usually) SQL. A relationship, on the other hand, is a link, or association, between elements. RDBs allow you to model relationships relatively easily thru either relational operations: SELECT * from cars, steering_wheels WHERE steering_wheels.carId = car.carId AND steering_wheels.wheelType = "sport" or by storing relationship information in relations (sometimes known as "link relations" or "link tables"): SELECT * from enrollments, classes, students WHERE classes.classId = enrollments.classId AND enrollments.studentId = students.studentId AND students.studentName = "Jason Corbett" But RDBs themselves have absolutely no concept of "relationships". So, next time you read the word "relation", think "table" :-) ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] relations in objects
Thanks for your reply. I've actually been thinking in an object oriented form for a while. I've looked at implimenting this project in Java using either prevailance or a object persistence model that mapped to a RDBMS. I like the idea of zope, so maybe I should clarify my question: How does an object in zope know where it sits in the hirearchy, and how does it reach other objects. That's what I'm really looking for, I can probably code the rest of the parts. Jason Corbett --- [EMAIL PROTECTED] wrote: > Hi Jason, > > I am not a zope developer, I am a semi-new user who > started with zope > coming from the same mindset as yourself. One of the > biggest challanges(at > least for me) is to wrap your mind around object > oriented programming. The > zope database is an object oriented database. This > means that you will > want/need to design your product differently than if > you were using > mysql/php to present and store your data. Think of > the information you > want to track as real world objects, and it is. Then > think about how these > real world objects relate to one another. You will > start to see a pattern. > Use this pattern to create a hierarchical > folder(object) structure. This > structure along with python's object inheritance > will allow you to develop > your relationships. Play with zope. Write your > product. Discover that you > need to rewrite your product because you did not > understand some > fundamentals. Complete the rewrite. Rinse and repeat > until you get it > right. > > Cheers, > Mike > > > Hello Zope developers, > > > > I'm a newbie (sorry most people have this curse > at > > one point or another). I have read the zope book > (or > > at least most of it), and the zope developer > manual. > > I can't quite figure out how to have relationships > > between instances of classes in the database. > > > > Let me first ask if I'm using zope for the > correct > > thing. I see that a lot of zope products deal > with > > content management, while mine doesn't really. > > Basically I want to do what I would normally do > with > > mysql and php, but use zope instead. So I need a > way > > to reference in some intelligent way between > objects > > in zope, and I need a way to query for a list of > them. > > > > I read about ZCatalogs, etc and how you can use > that > > for querying and indexing. That isn't my first > > priority, so I'll worry about that a little later. > > > > Basically I have an instance of a class 'A'. As > > part of it I need to reference either a single or > in > > some cases multiple instances of class 'B'. > Basically > > I'll have a mix of one-to-one relations and > > one-to-many. When I'm coding my python class (I'm > > going to do a product if you can't tell), how > would I > > get a list of the 'B' instances that relate to > this > > object, and how would I store that? The zope > > developer manual was pretty good for writing > classes, > > and making views on it, but I need to be able to > call > > methods on those instances and return lists of > them. > > > > Sorry for the long email, I just don't want to > leave > > details out. If you think I'm barking up the > wrong > > tree, and shouldn't be using zope for this, don't > be > > afraid to let me know. Although I will be pretty > > disappointed, I think zope is exactly what I've > been > > looking for, I can't find anything like it in any > > other language. > > > > Jason Corbett > > > > __ > > Do you Yahoo!? > > The New Yahoo! Shopping - with improved product > search > > http://shopping.yahoo.com > > > > ___ > > Zope-Dev maillist - [EMAIL PROTECTED] > > http://mail.zope.org/mailman/listinfo/zope-dev > > ** No cross posts or HTML encoding! ** > > (Related lists - > > > http://mail.zope.org/mailman/listinfo/zope-announce > > http://mail.zope.org/mailman/listinfo/zope ) > > > = . _ ___ / __// / (_)__ __ __ / /_/ __ / /__/ / _ \/ // /\ \/ / /_//_/ //_/_//_/\_,_/ /_/\_\ /_/ === Caldera OpenLinux __ Do you Yahoo!? The New Yahoo! Shopping - with improved product search http://shopping.yahoo.com ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] relations in objects
Hi Jason, I am not a zope developer, I am a semi-new user who started with zope coming from the same mindset as yourself. One of the biggest challanges(at least for me) is to wrap your mind around object oriented programming. The zope database is an object oriented database. This means that you will want/need to design your product differently than if you were using mysql/php to present and store your data. Think of the information you want to track as real world objects, and it is. Then think about how these real world objects relate to one another. You will start to see a pattern. Use this pattern to create a hierarchical folder(object) structure. This structure along with python's object inheritance will allow you to develop your relationships. Play with zope. Write your product. Discover that you need to rewrite your product because you did not understand some fundamentals. Complete the rewrite. Rinse and repeat until you get it right. Cheers, Mike > Hello Zope developers, > > I'm a newbie (sorry most people have this curse at > one point or another). I have read the zope book (or > at least most of it), and the zope developer manual. > I can't quite figure out how to have relationships > between instances of classes in the database. > > Let me first ask if I'm using zope for the correct > thing. I see that a lot of zope products deal with > content management, while mine doesn't really. > Basically I want to do what I would normally do with > mysql and php, but use zope instead. So I need a way > to reference in some intelligent way between objects > in zope, and I need a way to query for a list of them. > > I read about ZCatalogs, etc and how you can use that > for querying and indexing. That isn't my first > priority, so I'll worry about that a little later. > > Basically I have an instance of a class 'A'. As > part of it I need to reference either a single or in > some cases multiple instances of class 'B'. Basically > I'll have a mix of one-to-one relations and > one-to-many. When I'm coding my python class (I'm > going to do a product if you can't tell), how would I > get a list of the 'B' instances that relate to this > object, and how would I store that? The zope > developer manual was pretty good for writing classes, > and making views on it, but I need to be able to call > methods on those instances and return lists of them. > > Sorry for the long email, I just don't want to leave > details out. If you think I'm barking up the wrong > tree, and shouldn't be using zope for this, don't be > afraid to let me know. Although I will be pretty > disappointed, I think zope is exactly what I've been > looking for, I can't find anything like it in any > other language. > > Jason Corbett > > __ > Do you Yahoo!? > The New Yahoo! Shopping - with improved product search > http://shopping.yahoo.com > > ___ > Zope-Dev maillist - [EMAIL PROTECTED] > http://mail.zope.org/mailman/listinfo/zope-dev > ** No cross posts or HTML encoding! ** > (Related lists - > http://mail.zope.org/mailman/listinfo/zope-announce > http://mail.zope.org/mailman/listinfo/zope ) > ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] relations in objects
On Thu, Oct 09, 2003 at 05:07:28PM -0700, Jason Corbett wrote: > to reference in some intelligent way between objects > in zope, and I need a way to query for a list of them. google for mxmRelations. It does many-to-many relationships so yuo might have to modify it a bit if you really need to constrain that. -- Paul Winkler http://www.slinkp.com Look! Up in the sky! It's THE MAN! (random hero from isometric.spaceninja.com) ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] Initial ZODB permissions
On Wed, 2003-10-08 at 18:45, Andy McKay wrote: > > Yeah, wrong but toothless. Feel free to fix on appropriate branches I > > guess :-) > > Well yeah but Im betting its there for a reason, I just dont know what > it is yet. Changing that is sure to break something... The best I could find out is this snippet in Zope 2.6.2 CHANGES.txt - A new permission "Copy or Move" was added. This permission may be used respective to an object to prevent objects from being copyable or movable while within the management interface. The "old" behavior stipulated that users whom possessed the "View management screens" permission to an object's container could copy or move the object arbitrarily, even if they had limited access to the object itself. Once the object was moved or copied, the user became the owner of the new object, allowing them to see potentially sensitive information in the management interface for the object itself. This permission is granted to Manager and Anonymous by default, and must be revoked on an object-by-object basis if site managers intend to provide management screen access to folders which contain sensitive subobjects. This patch came as a result of Collector #376 (thanks to Chris Deckard). Cheers, Leo ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
[Zope-dev] relations in objects
Hello Zope developers, I'm a newbie (sorry most people have this curse at one point or another). I have read the zope book (or at least most of it), and the zope developer manual. I can't quite figure out how to have relationships between instances of classes in the database. Let me first ask if I'm using zope for the correct thing. I see that a lot of zope products deal with content management, while mine doesn't really. Basically I want to do what I would normally do with mysql and php, but use zope instead. So I need a way to reference in some intelligent way between objects in zope, and I need a way to query for a list of them. I read about ZCatalogs, etc and how you can use that for querying and indexing. That isn't my first priority, so I'll worry about that a little later. Basically I have an instance of a class 'A'. As part of it I need to reference either a single or in some cases multiple instances of class 'B'. Basically I'll have a mix of one-to-one relations and one-to-many. When I'm coding my python class (I'm going to do a product if you can't tell), how would I get a list of the 'B' instances that relate to this object, and how would I store that? The zope developer manual was pretty good for writing classes, and making views on it, but I need to be able to call methods on those instances and return lists of them. Sorry for the long email, I just don't want to leave details out. If you think I'm barking up the wrong tree, and shouldn't be using zope for this, don't be afraid to let me know. Although I will be pretty disappointed, I think zope is exactly what I've been looking for, I can't find anything like it in any other language. Jason Corbett __ Do you Yahoo!? The New Yahoo! Shopping - with improved product search http://shopping.yahoo.com ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] _p_deactivate() and _v_ variables?
Chris Withers wrote at 2003-10-8 21:22 +0100: > Casey Duncan wrote: > > > I would argue that a better plan would be to only use _v_ vars for completely > > disposable data only. The application should expect that this values will be > > gone at any random time, not just at transaction boundaries. > > I agree with this. How do we go about find code that uses the assumption that > _v_ stuff won't change unless it's at a transaction boundary? This will invalidate many current uses: * use for database connections * use for skin data * ... Dieter ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
[Zope-dev] Creative Commons Support
Are there any plans or is there any interest in supporting the Creative Commons Licenses for metadata in Zope-documents? Has there ever been any talk of such a product? Examples of applications with built-in CC support: http://creativecommons.org/technology/ccapps Greets, Wouter Vanden Hove www.open-education.org ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] _p_deactivate() and _v_ variables?
> > I would argue that a better plan would be to only use _v_ vars for completely > > disposable data only. The application should expect that this values will be > > gone at any random time, not just at transaction boundaries. > > I agree with this. How do we go about find code that uses the assumption that > _v_ stuff won't change unless it's at a transaction boundary? Note that we had a problem related to this with a client recently: In CMF, skin data is stored in portal._v_skindata, and is actually needed for the whole request, but in some ZEO setting this go cleared by a get_transaction().commit(1) which was unexpected and led to breakage because in that batch treatment we used some skin methods too... We ended up calling portal.setupCurrentSkin() after the commit() to reset the skins. FYI. Florent -- Florent Guillaume, Nuxeo (Paris, France) +33 1 40 33 79 87 http://nuxeo.com mailto:[EMAIL PROTECTED] ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] Initial ZODB permissions
Andy McKay wrote: Yeah, wrong but toothless. Feel free to fix on appropriate branches I guess :-) Well yeah but Im betting its there for a reason, I just dont know what it is yet. Changing that is sure to break something... Well, do it and I'm sur we'll soon find out :-) Chris ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
