December 2000 - Zope-Dev

Re: [Zope-dev] FW: ZPatterns, ObjectDomain, UML and all that.....
by Roch'e Compaan 05 Dec '00

05 Dec '00

> If you want to store one DataSkin inside another, where either one of them > is stored in a Rack, you will have to create appropriate SkinScript or > custom attribute providers to do so. But what if I always store dataskins in there own racks but simply assign an attribute of one Dataskin to the instance of another Dataskin? I simply want to be able to say Customer.Address.Street... > > > >PS: I checked Rack.py: > > > >CreateItem call _RawItem and in _RawItem the Rack for that instance is set: > > item._setRack(Self) # Connect to Rack > > > >I might be wrong but after a quick look at the attributehandling code in > >Dataskins.py suggests that the Dataskin does not know who its datamanager > >is. > > Yes, it does. _setRack() is called whenever a DataSkin is retrieved from a I meant to say "it DOES know" - but I do NOT :) Roché

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RE: [Zope-dev] time-travel how to?
by Damien Morton 05 Dec '00

05 Dec '00

Thanks for the tip. Yes, the HistoricalRevisions subsystem looks interesting. Im not sure it solves my problem though, in that the revisions seem to be for a single given object, rather than for a given subtree or site. They certainly dont seem to apply to folderish objects. For my application, making read-only restrictions on time-travel is perfectly acceptable, so I dont believe that paradoxes are of concern. Anyone have any suggestions about where to start with this? > -----Original Message----- > From: Shane Hathaway [mailto:shane@digicool.com] > Sent: Tuesday, December 05, 2000 11:05 AM > To: zope-dev(a)zope.org > Subject: Re: [Zope-dev] time-travel how to? > > > Damien Morton wrote: > > > > How do you access the fabled time travel features of Zope? > > > > Reading through the source I see that you can open a > database in read only > > mode and specify the point in time that that view is for. > > > > Would it be possible to mount the same data.fs multiple > times in read-only > > mode, each mounting with a different temporal view? > > > > Is there some other mechanism by which the time-travel > feature can be > > accessed? Ideally it would be possible to create a temporal > view of the > > database much like one would create a version, but that the > view would be > > enabled by traversing through that view in the URL. > > See the history tab of DTML methods. > > > For example, http://foo.com/nov3/x/y/z would be a view of > the database at > > nov3, where the actual time and date of the view would be > specified in the > > nov3 object. > > That would be spiffy! It would be fun to visit: > > http://mysite.com/HistoricalRevisions/2000Jan01/manage > > It's also very doable. Of course, time travel restrictions would have > to be imposed. (Zope will produce a "temporal paradox" > exception if you > do the right thing. It's something of an easter egg IMHO.) > > Shane > > _______________________________________________ > Zope-Dev maillist - Zope-Dev(a)zope.org > http://lists.zope.org/mailman/listinfo/zope-dev > ** No cross posts or HTML encoding! ** > (Related lists - > http://lists.zope.org/mailman/listinfo/zope-announce > http://lists.zope.org/mailman/listinfo/zope ) >

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time-travel how to?
by Damien Morton 05 Dec '00

05 Dec '00

How do you access the fabled time travel features of Zope? Reading through the source I see that you can open a database in read only mode and specify the point in time that that view is for. Would it be possible to mount the same data.fs multiple times in read-only mode, each mounting with a different temporal view? Is there some other mechanism by which the time-travel feature can be accessed? Ideally it would be possible to create a temporal view of the database much like one would create a version, but that the view would be enabled by traversing through that view in the URL. For example, http://foo.com/nov3/x/y/z would be a view of the database at nov3, where the actual time and date of the view would be specified in the nov3 object.

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FW: ZPatterns, ObjectDomain, UML and all that.....
by RC Compaan 05 Dec '00

05 Dec '00

(forgot to cc this to zope-dev) -----Original Message----- From: RC Compaan [mailto:sparroy@adept.co.za] Sent: 05 December 2000 03:17 To: steve(a)spvi.com Subject: RE: ZPatterns, ObjectDomain, UML and all that..... > Thanks... is that working between transactions? It has me a little > confused. I've been snooping through the implementation of ZPatterns > for a clue.... and it looks to me like: Well so far it seems to work fine... I do however receive a KeyError with one of my Dataskins but this is isolated to one particular Dataskin. I did not inspect the innards of ZPatterns that well, I must say, so this issue still remains unresolved to me as well. > a) the data manager for a DataSkin is a non-persistent attribute. > (self._v_dm_). I think this means that it needs to be set > somehow in every Zope transaction before you can do much of > anything with the instance. If this is the case then my current implementation will have to change quite dramatically :( I don't quite understand why Dataskins are implemented in this way - this obstructs natural object oriented programming? I would have thought that the datamanager is set when the a Dataskin is created. > RC> With Container/Content type objects I do roughly the same - I > RC> have setContainer methods for the Content objects. > > So most of your objects are defined in Python products, or are these > methods ExternalMethods? They are all external methods - I do most of my development with ZClasses and Python Methods make life a lot easier. Roché PS: I checked Rack.py: CreateItem call _RawItem and in _RawItem the Rack for that instance is set: item._setRack(Self) # Connect to Rack I might be wrong but after a quick look at the attributehandling code in Dataskins.py suggests that the Dataskin does not know who its datamanager is.

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RE: ZPatterns, ObjectDomain, UML and all that.....
by RC Compaan 05 Dec '00

05 Dec '00

Hi Steve I'm also a babe in the woods when it comes to object modelling, but here's my pennie's worth. Since code generation was not really required in the models I recently did for Zope Apps and the terrible exchange rate on the South African Rand I decided to use to very light weight Playground modelling tool. I agree with Steve Alexander that Coad notation serves ZPatterns *better* and this is exactly what Playground uses. > If I explicitly store a Bar object as an Attribute of a DataSkin then > what happens if the original Bar is removed from its Specialist's > Rack? Does the Bar I store still refer to the original Rack as its > DataManager? So.. does a Rack sometimes have 'clients' that are not > really in the Rack at all? Or perhaps I misunderstood the discussion, > and the Address wasn't really a DataSkin at all? Also.. assuming > that all works, do I have to do anything special, or carefully to be > sure that the persistence machinery doesn't incur lots of expensive > attribute fetching if I don't explicitly refer to those attributes, > but have the DataSkin as a directly set attribute of another > DataSkin? Before I started building Apps with ZPatterns I built a object/relational access layer in Delphi for my applications which enables me to create pure objects in my problem domain and delegate all data management to the the access layer. I *think* this is one of the things ZPatterns wants to do as well. Take the Customer with Address property example: I create Customer and Address Dataskins. For Customer I have an external method setAddress which sets the Address property of my Customer object and this is how I would create a new Customer: newCustomer = customerRack.newItem( CustomerCounter ) newAddress = addressRack.newItem( AddressCounter ) newCustomer.setAddress( newAddress ) I prefer the simplicity this brings when I have to access the properties of a Customer (without having to call a getter each time I need an address): myCustomer.Address.Street This also maps quite simply to SQL storage. So although instances of Address are properties of Customer they live on their own Rack and instances of Customer simply refers to their Address through assignment. With Container/Content type objects I do roughly the same - I have setContainer methods for the Content objects. Roché

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debugging authentication problems
by Toby Dickenson 05 Dec '00

05 Dec '00

Im have trouble tracking down why one specific method is needing authentication. Can anyone suggest any tips or tools? Toby Dickenson tdickenson(a)geminidataloggers.com

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Re: [Zope-dev] standard_error_message does nothing?
by simuran＠home.com 05 Dec '00

05 Dec '00

Well, I'll try to share some Zope zen obtained after fighting with "weird standard_error_message behaviour" phenomena. It might sound very weird, but to make standard_error_message behave it should/you expect it to, it must contain sufficient HTML to properly show itself. Don't ask why... I don't know :) Seems that this works fine: [standard_error_message] <html> <body> <dtml-var error_type> </body></html> In contrast with following, which does not work as expected: [standard_error_message] <dtml-var standard_html_header> <dtml-var error_type> <dtml-var standard_html_footer> [standard_html_header] <html> <body> [standard_html_footer] </body></html> Though, you need to make sure that any DTML code included in standard_error_message would not raise any exceptions (NotFound, KeyError etc...). In this case Zope will render error message that is defined in _error_html() in HTTPResponse.py, which is fine. OTOH, above hack works with almost all error types, but Unauthorized. Can anyone provide any sound explanation? Also, are there any _proper_ ways of redefining error message in Products? And why is it so, that (at least in 2.2.x) you can not remove standard_html_[header|footer] from Zope root? Does it have anything to do with being mentioned in /standard_error_message? Regards, Alex. -- Complex problems have simple, easy-to-understand wrong answers.

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ZPetterns implementation qustions
by Itai Tavor 05 Dec '00

05 Dec '00

Hi, I'm trying to figure out the right way to implement a set of classes and roles in ZPatterns. I asked some questions about this a while ago, and then went away and did some learning, but I'm stuck again and I'm afraid I need to ask more questions. I have two types of actors - Person (with properties name, phone, email, password) and Organization (with properties name, phone, fax, business_number). I also have two participants - Customer and Reseller. Each participant can be either a Person or an Organization. The participants can fill several roles, like OrderingEntities, BillableEntities, etc. Starting from the bottom, I create a Specialist for each role, each one with two virtual Racks - customerRack and ResellerRack, so I can refer to an OrderingEntity without caring if it's a Reseller or Customer. My problem is in implementing the Participant Specialists and storing Participant and Actor classes. Do I create Specialists for the Actors? It seems to me that since there is either one Person or one Organization per Customer, then the actor object should be created in the Customers Specialist. So Customers will have 3 Racks - defaultRack (using Customer object), personRack (using Person object) and organizationRack (using Organization object). Does this make sense? If this is a good way to do it, how do I handle creating and accessing the Person and Organization objects? Do I call personRack.newItem(newCustomerId) in the script that creates the customer? Or do I somehow do it in a SkinScript in defaultRack? And how do I get to the Person data? With an attribute provider? Or in the SkinScript: WITH personRack.getItem(self.id) COMPUTE name=name, phone=phone, email=email, password=password, personObject=RESULT) Also, if Actors are stored in the Specialists that implement the roles they participate as, there is no place to store methods that are common to an Actor regardless of role - for example, a method that checks if a password is secure enough and called when adding a Person object. So I either duplicate these methods in every Participant Specialist, or create more Specialists - which seems like a waste either way. Another problem is how to edit these objects - if I have a form which includes fields for a Customer properties and for the properties of the Person object linked to that Customer, can I change the Person object from the Customer SkinScript? I don't think I can do this: WHEN OBJECT CHANGED STORE name, password USING personObject.propertysheets.manage_changeProperties(name=self.name, password=self.password) Right? Because name and password are not properties on the Customer DataSkin. So I have to call person.manage_changeProperties(...) in the method that changes Customer... it seems to me that I always end up doing object connections work in methods and the SkinScript can't help with anything :( Hope this is not too convoluted...I'd really appreciate any help anyone can offer. The existing ZPatterns examples all deal with fairly straightforward situations, but it's the more complex class relationships where the bears and tigers are hiding :) Itai -- Itai Tavor "Je sautille, donc je suis." C3Works itai(a)c3works.com - Kermit the Frog "If you haven't got your health, you haven't got anything"

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Re: [Zope-dev] ZPatterns, ObjectDomain, UML and all that.....
by Itai Tavor 04 Dec '00

04 Dec '00

Steve Spicklemire wrote: >I've been working out some issues with EMarket, and as a way to 'clear >the cruft'.. I decided to bite the bullet and do some more careful >object modeling. Other than scribbling on paper, and making up some >diagrams that look a little like those from Coad's book on Patterns >and Strategies, I've never used any object modeling tools before in my >life. Soooo... I downloaded the eval version of ObjectDomain, and I >can go for about 5 minutes on a Mac before it crashes, and usually 10 >or 15 on Windows before it stops responding to mouse/keyboard >input. Save early, save often.. ;->. Sure it's frustrating.... but it >seems more workable that ArgoUML which I've had even less luck >with.... (What are other folks using? Rose?) anyway after much more >time that I would have thought possible I've come up with: I'm in about the same position as you right now - trying to learn formal object modeling and ZPatterns, so I'm not qualified to say anything about your model or questions... I just want to mention two things that I found: - I didn't find any of the modeling tools you mentioned, or others I've tried, very useful on a Mac (or at all), and I ended up using ConceptDraw, which is a general purpose drawing tool with UML and Coad libraries. - Steve Alexander wrote in a reply to your post: >I think Coad's notation is better and clearer, as it allows you to >communicate information about objects and their classes all in one >place. Coad's notation is more about showing interactions of objects, >whereas UML makes that awkward, and is mostly used for expressing static >information about relationships between classes. Very true, IMVHO. I still find there's a big gap between a Coad model and a ZPatterns implementation, but it's much better than with UML. HTH -- Itai Tavor "Je sautille, donc je suis." C3Works itai(a)c3works.com - Kermit the Frog "If you haven't got your health, you haven't got anything"

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Suggestion: All wiki pages have the last modified date in the foo ter. ter.
by Jay, Dylan 04 Dec '00

04 Dec '00

There is getting to be some out of date content and it would be great to see which is which. ---- Dylan Jay mailto:djay@avaya.com Avaya Communication Tel: +61 2 9886-8961 Level 5, 15 Talavera Road FAX: +61 2 9352 9224 Nth Ryde NSW 2113 Mobile:0409 606 171 AUSTRALIA

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