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• how to improve design ability

  - by Cong Hui

  I recently went on a couple of interviews and all of them asked a one or two design questions, like how you would design a chess, monopoly, and so on. I didn't do good on those since I am a college student and lack of the experience of implementing big and complex systems. I figure the only way to improve my design capability is to read lots of others' code and try to implement myself. Therefore, for those companies that ask these questions, what are their real goals in this? I figure most of college grads start off working in a team guided by a senior leader in their first jobs. They might not have lots of design experience fresh out of colleges. Anyone could give pointers about how to practice those skills? Thank you very much

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• avoid the use of 'mixed=true' in xml schema

  - by Ralph Kretzler

  I am using xjc to convert a schema to java classes. When I am using mixed=true in the schema I am losing the access method for child nodes instead there is a single general content access method. Is there a way to rewrite the schema without using mixed=true. There is no way that I can change the xml so I have to customize the schema. Schema XML camera or camera Thanks, Ralph

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• How To Deal With Terrible Design Decisions

  - by splatto

  I'm a consultant at one company. There is another consultant who is a year older than me and has been here 3 months longer than I have, and a full time developer. The full-time developer is great. My concern is that I see the consultant making absolutely terrible design decisions. For example, M:M relationships are being stored in the database as a comma-delimited string rather than using a conjunction table to hold the relationships. For example, consider two tables, Car and Property: Car records: Camry Volvo Mercedes Property records: Spare Tire Satellite Radio Ipod Support Standard Rather than making a table CarProperties to represent this, he has made a "Property" attribute on the Car table whose data looks like "1,3,7,13,19,25," I hate how this decision and others are affecting the quality of my code. We have butted heads over this design three times in the past two months since I've been here. He asked me why my suggestion was better, and I responded that our database would be eliminating redundant data by converting to a higher normal form. I explained that this design flaw in particular is discussed and discouraged in entry level college programs, and he responded with a shot at me saying that these comma-separated-value database properties are taught when you do your masters (which neither of us have). Needless to say, he became very upset and demanded I apologize for criticizing his work, which I did in the interest of not wanting to be the consultant to create office drama. Our project manager is focused on delivering a product ASAP and is a very strong personality - Suggesting to him at this point that we spend some time to do this right will set him off. There is a strong likelihood that both of our contracts will be extended to work on a second project coming up. How will I be able to exert dominant influence over the design of the system and the data model to ensure that such terrible mistakes are not repeated in the next project? A glimpse at the dynamics: I can be a strong personality if I don't measure myself. The other consultant is not a strong personality, is a poor communicator, is quite stubborn and thinks he is better than everyone else. The project manager is an extremely strong personality who is focused on releasing tomorrow's product yesterday. The full-time developer is very laid back and easy going, a very effective communicator, but is someone who will accept bad design if it means not rocking the boat. Code reviews or anything else that takes "time" will be out of the question - there is no way our PM will be sold on such a thing by anybody.

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• Refactoring in domain driven design

  - by Andrew Whitaker

  I've just started working on a project and we're using domain-driven design (as defined by Eric Evans in Domain-Driven Design: Tackling Complexity in the Heart of Software. I believe that our project is certainly a candidate for this design pattern as Evans describes it in his book. I'm struggling with the idea of constantly refactoring. I know refactoring is a necessity in any project and will happen inevitably as the software changes. However, in my experience, refactoring occurs when the needs of the development team change, not as understanding of the domain changes ("refactoring to greater insight" as Evans calls it). I'm most concerned with breakthroughs in understanding of the domain model. I understand making small changes, but what if a large change in the model is necessary? What's an effective way of convincing yourself (and others) you should refactor after you obtain a clearer domain model? After all, refactoring to improve code organization or performance could be completely separate from how expressive in terms of the ubiquitous language code is. Sometimes it just seems like there's not enough time to refactor. Luckily, SCRUM lends it self to refactoring. The iterative nature of SCRUM makes it easy to build a small piece and change and it. But over time that piece will get larger and what if you have a breakthrough after that piece is so large that it will be too difficult to change? Has anyone worked on a project employing domain-driven design? If so, it would be great to get some insight on this one. I'd especially like to hear some success stories, since DDD seems very difficult to get right. Thanks!

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• A design pattern for data binding an object (with subclasses) to asp.net user control

  - by Rohith Nair

  I have an abstract class called Address and I am deriving three classes ; HomeAddress, Work Address, NextOfKin address. My idea is to bind this to a usercontrol and based on the type of Address it should bind properly to the ASP.NET user control. My idea is the user control doesn't know which address it is going to present and based on the type it will parse accordingly. How can I design such a setup, based on the fact that, the user control can take any type of address and bind accordingly. I know of one method like :- Declare class objects for all the three types (Home,Work,NextOfKin). Declare an enum to hold these types and based on the type of this enum passed to user control, instantiate the appropriate object based on setter injection. As a part of my generic design, I just created a class structure like this :- I know I am missing a lot of pieces in design. Can anybody give me an idea of how to approach this in proper way.

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• How to design database having multiple interrelated entities

  - by Sharath Chandra

  I am designing a new system which is more of a help system for core applications in banks or healthcare sector. Given the nature of the system this is not a heavy transaction oriented system but more of read intensive. Now within this application I have multiple entities which are related to each other. For e.g. Assume the following entities in the system User Training Regulations Now each of these entities have M:N Relationship with each other. Assuming the usage of a standard RDBMS, the design may involve many relationship tables each containing the relationships one other entity ("User_Training", "User_Regulations", "Training_Regulations"). This design is limiting since I have more than 3 entities in the system and maintaining the relationship graph is difficult this way. The most frequently used operation is "given an entity get me all the related entities" . I need to design the database where this operation is relatively inexpensive. What are the different recommendations for modelling this kind of database.

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• Requesting feedback on my OO design

  - by Prog

  I'm working on an application that creates music by itself. I'm seeking feedback for my OO design so far. This question will focus on one part of the program. The application produces Tune objects, that are the final musical products. Tune is an abstract class with an abstract method play. It has two subclasses: SimpleTune and StructuredTune. SimpleTune owns a Melody and a Progression (chord sequence). It's play implementation plays these two objects simultaneously. StructuredTune owns two Tune instances. It's own play plays the two Tunes one after the other according to a pattern (currently only ABAB). Melody is an abstract class with an abstract play method. It has two subclasses: SimpleMelody and StructuredMelody. SimpleMelody is composed of an array of notes. Invoking play on it plays these notes one after the other. StructuredMelody is composed of an array of Melody objects. Invoking play on it plays these Melodyies one after the other. I think you're starting to see the pattern. Progression is also an abstract class with a play method and two subclasses: SimpleProgression and StructuredProgression, each composed differently and played differently. SimpleProgression owns an array of chords and plays them sequentially. StructuredProgression owns an array of Progressions and it's play implementation plays them sequentially. Every class has a corresponding Generator class. Tune, Melody and Progression are matched with corresponding abstract TuneGenerator, MelodyGenerator and ProgressionGenerator classes, each with an abstract generate method. For example MelodyGenerator defines an abstract Melody generate method. Each of the generators has two subclasses, Simple and Structured. So for example MelodyGenerator has a subclasses SimpleMelodyGenerator, with an implementation of generate that returns a SimpleMelody. (It's important to note that the generate methods encapsulate complex algorithms. They are more than mere factory method. For example SimpleProgressionGenerator.generate() implements an algorithm to compose a series of Chord objects, which are used to instantiate the returned SimpleProgression). Every Structured generator uses another generator internally. It is a Simple generator be default, but in special cases may be a Structured generator. Parts of this design are meant to allow the end-user through the GUI to choose what kind of music is to be created. For example the user can choose between a "simple tune" (SimpleTuneGenerator) and a "full tune" (StructuredTuneGenerator). Other parts of the system aren't subject to direct user-control. What do you think of this design from an OOD perspective? What potential problems do you see with this design? Please share with me your criticism, I'm here to learn. Apart from this, a more specific question: the "every class has a corresponding Generator class" part feels very wrong. However I'm not sure how I could design this differently and achieve the same flexibility. Any ideas?

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• Active Directory and Apple's Workgroup Manager

  - by qbn

  I thought I'd share my experiences here. I work for a small business with only ~20 users. I wanted the ability to use managed client preferences to assign things like the software update server. Basically the ability to manage my Macs easily and in a native way. At first I tried the magic triangle solution, but I found this to be very complicated. Not only does it require a Mac OS X Server, but it gives you two points of failure. Additionally each Mac workstation must be bound to both servers. Eventually I sucked it up and went with the schema changes documented here. I was hesitant at first, because the instructions require a lot of manual work. However it was fairly basic and only took me about an hour and a half. Below you'll find the schema changes file that was a result of my work. I followed the instructions exactly and double checked everything, after six months of having this in place things have been running great. Too good to not share. I hope I save someone a couple of hours. # ================================================================== # # This file should be imported with the following command: # ldifde -i -u -f Apple AD Schema Changes.ldf -s server:port -b username domain password -j . -c "cn=Configuration,dc=X" #configurationNamingContext # LDIFDE.EXE from AD/AM V1.0 or above must be used. # This LDIF file should be imported into AD or AD/AM. It may not work for other directories. # # ================================================================== # ================================================================== # Attributes # ================================================================== # Attribute: apple-category dn: cn=apple-category,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.10.4 ldapDisplayName: apple-category attributeSyntax: 2.5.5.12 adminDescription: Category for the computer or neighborhood oMSyntax: 64 systemOnly: FALSE # Attribute: apple-computeralias dn: cn=apple-computeralias,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.20.3 ldapDisplayName: apple-computeralias attributeSyntax: 2.5.5.12 adminDescription: XML plist referring to a computer record oMSyntax: 64 systemOnly: FALSE # Attribute: apple-computer-list-groups dn: cn=apple-computer-list-groups,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.11.4 ldapDisplayName: apple-computer-list-groups attributeSyntax: 2.5.5.12 adminDescription: groups oMSyntax: 64 systemOnly: FALSE # Attribute: apple-computers dn: cn=apple-computers,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.11.3 ldapDisplayName: apple-computers attributeSyntax: 2.5.5.12 adminDescription: computers oMSyntax: 64 systemOnly: FALSE # Attribute: apple-data-stamp dn: cn=apple-data-stamp,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.12.2 ldapDisplayName: apple-data-stamp attributeSyntax: 2.5.5.5 adminDescription: data stamp oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-dns-domain dn: cn=apple-dns-domain,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.18.1 ldapDisplayName: apple-dns-domain attributeSyntax: 2.5.5.12 adminDescription: DNS domain oMSyntax: 64 systemOnly: FALSE # Attribute: apple-dnsname dn: cn=apple-dnsname,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.19.4 ldapDisplayName: apple-dnsname attributeSyntax: 2.5.5.12 adminDescription: DNS name oMSyntax: 64 systemOnly: FALSE # Attribute: apple-dns-nameserver dn: cn=apple-dns-nameserver,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.18.2 ldapDisplayName: apple-dns-nameserver attributeSyntax: 2.5.5.12 adminDescription: DNS name server list oMSyntax: 64 systemOnly: FALSE # Attribute: apple-group-homeowner dn: cn=apple-group-homeowner,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.14.2 ldapDisplayName: apple-group-homeowner attributeSyntax: 2.5.5.5 adminDescription: group home owner settings oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-group-homeurl dn: cn=apple-group-homeurl,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.14.1 ldapDisplayName: apple-group-homeurl attributeSyntax: 2.5.5.5 adminDescription: group home url oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-imhandle dn: cn=apple-imhandle,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.21 ldapDisplayName: apple-imhandle attributeSyntax: 2.5.5.12 adminDescription: IM handle (service:account name) oMSyntax: 64 systemOnly: FALSE # Attribute: apple-keyword dn: cn=apple-keyword,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.19 ldapDisplayName: apple-keyword attributeSyntax: 2.5.5.12 adminDescription: keywords oMSyntax: 64 systemOnly: FALSE # Attribute: apple-mcxflags dn: cn=apple-mcxflags,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.10 ldapDisplayName: apple-mcxflags attributeSyntax: 2.5.5.12 adminDescription: mcx flags oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-mcxsettings dn: cn=apple-mcxsettings,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.16 ldapDisplayName: apple-mcxsettings attributeSyntax: 2.5.5.12 adminDescription: mcx settings oMSyntax: 64 systemOnly: FALSE # Attribute: apple-neighborhoodalias dn: cn=apple-neighborhoodalias,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.20.2 ldapDisplayName: apple-neighborhoodalias attributeSyntax: 2.5.5.12 adminDescription: XML plist referring to another neighborhood record oMSyntax: 64 systemOnly: FALSE # Attribute: apple-networkview dn: cn=apple-networkview,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.10.3 ldapDisplayName: apple-networkview attributeSyntax: 2.5.5.12 adminDescription: Network view for the computer oMSyntax: 64 systemOnly: FALSE # Attribute: apple-nodepathxml dn: cn=apple-nodepathxml,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.20.1 ldapDisplayName: apple-nodepathxml attributeSyntax: 2.5.5.12 adminDescription: XML plist of directory node path oMSyntax: 64 systemOnly: FALSE # Attribute: apple-service-location dn: cn=apple-service-location,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.19.5 ldapDisplayName: apple-service-location attributeSyntax: 2.5.5.12 adminDescription: Service location oMSyntax: 64 systemOnly: FALSE # Attribute: apple-service-port dn: cn=apple-service-port,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.19.3 ldapDisplayName: apple-service-port attributeSyntax: 2.5.5.9 adminDescription: Service port number oMSyntax: 2 systemOnly: FALSE # Attribute: apple-service-type dn: cn=apple-service-type,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.19.1 ldapDisplayName: apple-service-type attributeSyntax: 2.5.5.5 adminDescription: type of service oMSyntax: 22 systemOnly: FALSE # Attribute: apple-service-url dn: cn=apple-service-url,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.19.2 ldapDisplayName: apple-service-url attributeSyntax: 2.5.5.5 adminDescription: URL of service oMSyntax: 22 systemOnly: FALSE # Attribute: apple-user-authenticationhint dn: cn=apple-user-authenticationhint,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.15 ldapDisplayName: apple-user-authenticationhint attributeSyntax: 2.5.5.12 adminDescription: password hint oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-class dn: cn=apple-user-class,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.7 ldapDisplayName: apple-user-class attributeSyntax: 2.5.5.5 adminDescription: user class oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-homequota dn: cn=apple-user-homequota,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.8 ldapDisplayName: apple-user-homequota attributeSyntax: 2.5.5.5 adminDescription: home directory quota oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-homesoftquota dn: cn=apple-user-homesoftquota,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.17 ldapDisplayName: apple-user-homesoftquota attributeSyntax: 2.5.5.5 adminDescription: home directory soft quota oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-homeurl dn: cn=apple-user-homeurl,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.6 ldapDisplayName: apple-user-homeurl attributeSyntax: 2.5.5.5 adminDescription: home directory URL oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-mailattribute dn: cn=apple-user-mailattribute,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.9 ldapDisplayName: apple-user-mailattribute attributeSyntax: 2.5.5.12 adminDescription: mail attribute oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-picture dn: cn=apple-user-picture,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.12 ldapDisplayName: apple-user-picture attributeSyntax: 2.5.5.12 adminDescription: picture oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-user-printattribute dn: cn=apple-user-printattribute,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.13 ldapDisplayName: apple-user-printattribute attributeSyntax: 2.5.5.12 adminDescription: print attribute oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-webloguri dn: cn=apple-webloguri,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.1.22 ldapDisplayName: apple-webloguri attributeSyntax: 2.5.5.12 adminDescription: Weblog URI oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: apple-xmlplist dn: cn=apple-xmlplist,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.17.1 ldapDisplayName: apple-xmlplist attributeSyntax: 2.5.5.12 adminDescription: XML plist data oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: ipHostNumber dn: cn=ipHostNumber,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.1.1.1.19 ldapDisplayName: ipHostNumber attributeSyntax: 2.5.5.5 adminDescription: IP address oMSyntax: 22 systemOnly: FALSE rangeUpper: 128 # Attribute: macAddress dn: cn=macAddress,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.1.1.1.22 ldapDisplayName: macAddress attributeSyntax: 2.5.5.5 adminDescription: MAC address oMSyntax: 22 systemOnly: FALSE rangeUpper: 128 # Attribute: mountDirectory dn: cn=apple-mountDirectory,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.8.1 ldapDisplayName: mountDirectory attributeSyntax: 2.5.5.12 adminDescription: mount path oMSyntax: 64 isSingleValued: TRUE systemOnly: FALSE # Attribute: mountDumpFrequency dn: cn=apple-mountDumpFrequency,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.8.4 ldapDisplayName: mountDumpFrequency attributeSyntax: 2.5.5.5 adminDescription: mount dump frequency oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: mountOption dn: cn=apple-mountOption,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.8.3 ldapDisplayName: mountOption attributeSyntax: 2.5.5.5 adminDescription: mount options oMSyntax: 22 systemOnly: FALSE # Attribute: mountPassNo dn: cn=apple-mountPassNo,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.8.5 ldapDisplayName: mountPassNo attributeSyntax: 2.5.5.5 adminDescription: mount passno oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: mountType dn: cn=apple-mountType,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.63.1000.1.1.1.8.2 ldapDisplayName: mountType attributeSyntax: 2.5.5.5 adminDescription: mount VFS type oMSyntax: 22 isSingleValued: TRUE systemOnly: FALSE # Attribute: ttl dn: cn=ttl,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: attributeSchema attributeId: 1.3.6.1.4.1.250.1.60 ldapDisplayName: ttl attributeSyntax: 2.5.5.9 oMSyntax: 2 isSingleValued: TRUE systemOnly: FALSE dn: changetype: modify add: schemaUpdateNow schemaUpdateNow: 1 - # ================================================================== # Classes # ================================================================== # Class: apple-computer dn: cn=apple-computer,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.10 ldapDisplayName: apple-computer adminDescription: computer objectClassCategory: 3 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-category mayContain: 1.3.6.1.4.1.63.1000.1.1.1.10.4 # mayContain: apple-computer-list-groups mayContain: 1.3.6.1.4.1.63.1000.1.1.1.11.4 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-mcxflags mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.10 # mayContain: apple-mcxsettings mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.16 # mayContain: apple-networkview mayContain: 1.3.6.1.4.1.63.1000.1.1.1.10.3 # mayContain: apple-service-url mayContain: 1.3.6.1.4.1.63.1000.1.1.1.19.2 # mayContain: apple-xmlplist mayContain: 1.3.6.1.4.1.63.1000.1.1.1.17.1 # mayContain: macAddress mayContain: 1.3.6.1.1.1.1.22 # mayContain: ttl mayContain: 1.3.6.1.4.1.250.1.60 # Class: apple-computer-list dn: cn=apple-computer-list,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.11 ldapDisplayName: apple-computer-list adminDescription: computer list objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-computer-list-groups mayContain: 1.3.6.1.4.1.63.1000.1.1.1.11.4 # mayContain: apple-computers mayContain: 1.3.6.1.4.1.63.1000.1.1.1.11.3 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-mcxflags mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.10 # mayContain: apple-mcxsettings mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.16 possSuperiors: organizationalUnit possSuperiors: container # Class: apple-configuration dn: cn=apple-configuration,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.12 ldapDisplayName: apple-configuration adminDescription: configuration objectClassCategory: 3 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-data-stamp mayContain: 1.3.6.1.4.1.63.1000.1.1.1.12.2 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-xmlplist mayContain: 1.3.6.1.4.1.63.1000.1.1.1.17.1 # mayContain: ttl mayContain: 1.3.6.1.4.1.250.1.60 possSuperiors: organizationalUnit possSuperiors: container # Class: apple-group dn: cn=apple-group,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.14 ldapDisplayName: apple-group adminDescription: group account objectClassCategory: 3 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-group-homeowner mayContain: 1.3.6.1.4.1.63.1000.1.1.1.14.2 # mayContain: apple-group-homeurl mayContain: 1.3.6.1.4.1.63.1000.1.1.1.14.1 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-mcxflags mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.10 # mayContain: apple-mcxsettings mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.16 # mayContain: apple-user-picture mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.12 # mayContain: ttl mayContain: 1.3.6.1.4.1.250.1.60 # Class: apple-location dn: cn=apple-location,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.18 ldapDisplayName: apple-location objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-dns-domain mayContain: 1.3.6.1.4.1.63.1000.1.1.1.18.1 # mayContain: apple-dns-nameserver mayContain: 1.3.6.1.4.1.63.1000.1.1.1.18.2 possSuperiors: organizationalUnit possSuperiors: container # Class: apple-neighborhood dn: cn=apple-neighborhood,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.20 ldapDisplayName: apple-neighborhood objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-category mayContain: 1.3.6.1.4.1.63.1000.1.1.1.10.4 # mayContain: apple-computeralias mayContain: 1.3.6.1.4.1.63.1000.1.1.1.20.3 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-neighborhoodalias mayContain: 1.3.6.1.4.1.63.1000.1.1.1.20.2 # mayContain: apple-nodepathxml mayContain: 1.3.6.1.4.1.63.1000.1.1.1.20.1 # mayContain: apple-xmlplist mayContain: 1.3.6.1.4.1.63.1000.1.1.1.17.1 # mayContain: ttl mayContain: 1.3.6.1.4.1.250.1.60 possSuperiors: 2.5.6.5 possSuperiors: container # Class: apple-serverassistant-config dn: cn=apple-serverassistant-config,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.17 ldapDisplayName: apple-serverassistant-config objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-xmlplist mayContain: 1.3.6.1.4.1.63.1000.1.1.1.17.1 possSuperiors: organizationalUnit possSuperiors: container # Class: apple-service dn: cn=apple-service,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.19 ldapDisplayName: apple-service objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mustContain: apple-service-type mustContain: 1.3.6.1.4.1.63.1000.1.1.1.19.1 # mayContain: apple-dnsname mayContain: 1.3.6.1.4.1.63.1000.1.1.1.19.4 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-service-location mayContain: 1.3.6.1.4.1.63.1000.1.1.1.19.5 # mayContain: apple-service-port mayContain: 1.3.6.1.4.1.63.1000.1.1.1.19.3 # mayContain: apple-service-url mayContain: 1.3.6.1.4.1.63.1000.1.1.1.19.2 # mayContain: ipHostNumber mayContain: 1.3.6.1.1.1.1.19 possSuperiors: organizationalUnit possSuperiors: container # Class: apple-user dn: cn=apple-user,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.1 ldapDisplayName: apple-user adminDescription: apple user account objectClassCategory: 3 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: apple-imhandle mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.21 # mayContain: apple-keyword mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.19 # mayContain: apple-mcxflags mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.10 # mayContain: apple-mcxsettings mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.16 # mayContain: apple-user-authenticationhint mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.15 # mayContain: apple-user-class mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.7 # mayContain: apple-user-homequota mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.8 # mayContain: apple-user-homesoftquota mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.17 # mayContain: apple-user-homeurl mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.6 # mayContain: apple-user-mailattribute mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.9 # mayContain: apple-user-picture mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.12 # mayContain: apple-user-printattribute mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.13 # mayContain: apple-webloguri mayContain: 1.3.6.1.4.1.63.1000.1.1.1.1.22 # Class: mount dn: cn=apple-mount,cn=Schema,cn=Configuration,dc=X changetype: ntdsschemaadd objectClass: classSchema governsID: 1.3.6.1.4.1.63.1000.1.1.2.8 ldapDisplayName: mount objectClassCategory: 1 # subclassOf: top subclassOf: 2.5.6.0 # rdnAttId: cn rdnAttId: 2.5.4.3 # mayContain: mountDirectory mayContain: 1.3.6.1.4.1.63.1000.1.1.1.8.1 # mayContain: mountDumpFrequency mayContain: 1.3.6.1.4.1.63.1000.1.1.1.8.4 # mayContain: mountOption mayContain: 1.3.6.1.4.1.63.1000.1.1.1.8.3 # mayContain: mountPassNo mayContain: 1.3.6.1.4.1.63.1000.1.1.1.8.5 # mayContain: mountType mayContain: 1.3.6.1.4.1.63.1000.1.1.1.8.2 possSuperiors: 2.5.6.5 possSuperiors: container dn: changetype: modify add: schemaUpdateNow schemaUpdateNow: 1 - # ================================================================== # Updating present elements # ================================================================== # Add the new class to the user object dn: CN=User,CN=Schema,CN=Configuration,DC=X changetype: modify add: auxiliaryClass auxiliaryClass: apple-user - # Add the new class to the computer object dn: CN=Computer,CN=Schema,CN=Configuration,DC=X changetype: modify add: auxiliaryClass auxiliaryClass: apple-computer - # Add the new class to the group object dn: CN=Group,CN=Schema,CN=Configuration,DC=X changetype: modify add: auxiliaryClass auxiliaryClass: apple-group - # Add the new class to the configuration object dn: CN=Configuration,CN=Schema,CN=Configuration,DC=X changetype: modify add: auxiliaryClass auxiliaryClass: apple-configuration -

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• Is Design Pattern only for Object-Oriented design?

  - by Tim

  I was wondering if all design Patterns are only used in Object-Oriented design? Are there any design patterns used in non Object-Oriented design? Thanks and regards!

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• New design patterns/design strategies

  - by steven

  I've studied and implemented design patterns for a few years now, and I'm wondering. What are some of the newer design patterns (since the GOF)? Also, what should one, similar to myself, study [in the way of software design] next? Note: I've been using TDD, and UML for some time now. I'm curious about the newer paradigm shifts, and or newer design patterns.

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• Design Pattern Advice for Bluetooth App for Android

  - by Aimee Jones

  I’m looking for some advice on which patterns would apply to some of my work. I’m planning on doing a project as part of my college work and I need a bit of help. My main project is to make a basic Android bluetooth tracking system where the fixed locations of bluetooth dongles are mapped onto a map of a building. So my android app will regularly scan for nearby dongles and triangulate its location based on signal strength. The dongles location would be saved to a database along with their mac addresses to differentiate between them. The android phones location will then be sent to a server. This information will be used to show the phone’s location on a map of the building, or map of a route taken, on a website. My side project is to choose a suitable design pattern that could be implemented in this main project. I’m still a bit new to design patterns and am finding it hard to get my head around ones that may be suitable. I’ve heard maybe some that are aimed at web applications for the server side of things may be appropriate. My research so far is leading me to the following: Navigation Strategy Pattern Observer Pattern Command Pattern News Design Pattern Any advice would be a great help! Thanks

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• Authorization design-pattern / practice?

  - by Lawtonfogle

  On one end, you have users. On the other end, you have activities. I was wondering if there is a best practice to relate the two. The simplest way I can think of is to have every activity have a role, and assign every user every role they need. The problem is that this gets really messy in practice as soon as you go beyond a trivial system. A way I recently designed was to have users who have roles, and roles have privileges, and activities require some combinations of privileges. For the trivial case, this is more complex, but I think it will scale better. But after I implemented it, I felt like it was overkill for the system I had. Another option would be to have users, who have roles, and activities require you to have a certain role to perform with many activities sharing roles. A more complex variant of this would given activities many possible roles, which you only needed one of. And an even more complex variant would be to allow logical statements of role ownership to use an activity (i.e. Must have A and (B exclusive or C) and must not have D). I could continue to list more, but I think this already gives a picture. And many of these have trade offs. But in software design, there are oftentimes solutions, while perhaps not perfect in every possible case, are clearly top of the pack to an extent it isn't even considered opinion based (i.e. how to store passwords, plain text is worse, hashing better, hashing and salt even better, despite the increased complexity of each level) (i.e. 2, Smart UI designs for applications are bad, even if it is subjective as to what the best design is). So, is there a best practice for authorization design that is not purely opinion based/subjective?

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• Clean MVC design when there is viewer latency

  - by Tony Suffolk 66

  It isn't clear if this question has already been answered, so apologies in advance if this is a duplicate : I am implementing a game and trying to design around a clean MVC pattern - so my Control plane will implement the rules of the game (but not how the game is displayed), and the View plane implements how the game is displayed, and user iteraction - i.e. what game items or controls the user has activated. The challenge that I have is this : In my game the Control Plane can move game items more or less instaneously (The decision about what item to place where - and some of the initial consequences of that placement are reasonably trivial to calculate), but I want to design the Control Plane so that the View plane can display these movements either instaneously or using movement animations. The other complication is that player interaction must be locked out while those game items are moving (similar to chess - you can't attack an opposing piece as it moves past one of your pieces) So do I : Implement all the logic in the Control Plane asynchronously - and separate the descision making from the actions - so the Control plane decides piece 'A' needs to move to a given place - tells the view plane, and but does not implement the move in data until the view plane informs the control plane that the move/animation is complete. A lot of interlock points between the two layers. Implement all the control plane logic in one place - decisions and movement (keeping track of what moved where), and pass all the movements in one go to the View plane to do with what it will. Control Plane is almost fire and forget here. A hybrid of 1 & 2 - The control plane implements all the moves in a temporary data store - but maintains a second store which reflects what is actually visible to the viewer, based on calls and feedback from the View plane. All 3 are relatively easy to implement (target language is python), but having never done a clean MVC pattern with view latency before - I am not sure which design is best

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• Oracle Schema Design: Seperate Schema with I/O Overhead?

  - by Guru

  We are designing database schema for a new system based on Oracle 11gR1. We have identified a main schema which would have close to 100 tables, these will be accessed from the front end Java application. We have a requirement to audit the values which got changed in close to 50 tables, this has to be done every row. Which means, it is possible that, for a single row in MYSYS.T1 there might be 50 (or more) rows in MYSYS_AUDIT.T1_AUD table. We might be having old values of every column entry and new values available from T1. DBA gave an observation, advising against this method, because he said, separate schema meant an extra I/O for every operation. Basically AUDIT schema would be used only to do some analyse and enter values (thus SELECT and INSERT). Is it true that, "a separate schema means an extra I/O" ? I could not find justification. It appears logical to me, as the AUDIT data should not be tampered with, so a separate schema. Also, we designed a separate schema for archiving some tables from MYSYS. From MYSYS_ARC the table might be backed up into tapes or deleted after sufficient time. Few stats: Few tables (close to 20, 30) in MYSYS schema could grow to around 50M rows. We have asked for a total disk space of 4 TB. MYSYS_AUDIT schema might be having 10 times that of MYSYS but we wont keep them more than 3 months. Questions Given all these, can you suggest me any improvements? Separate schema affects disc I/O? (one extra I/O for every schema ?) Any general suggestions? Figure: +-------------------+ +-------------------+ | MYSYS | | MYSYS_AUDIT | | | | | | 1. T1 | | 1. T1_AUD | | 2. T2 | | 2. T2_AUD | | 3. T3 |--------->| 3. T3_AUD | | 4. T4 |(SELECT, | 4. T4_AUD | | . | INSERT) | . | | . | | . | | . | | . | | 100. T100 | | 50. T50_AUD | +-------------------+ +-------------------+ | | | | |(INSERT) | | | * +-------------------+ | MYSYS_ARC | | | | 1. T1_ARC | | 2. T2_ARC | | 3. T3_ARC | | 4. T4_ARC | | . | | . | | . | | 100. T100_ARC | +-------------------+ Apart from this, we have two more schemas with only read only rights, but mainly they are for adhoc purpose and we dont mind the performance on them.

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• Design Book–Dimensional or No Dimensional, that is..the question

  - by drsql

  So, it is right there in the title of the book “Relational Database Design” etc (the title is kinda long :)  But as I consider what to cover and, conversely, what not to cover, dimensional design inevitably pops up. So I am considering including it in the book. One thing I try to do is to cover topics to a level where you can start using it immediately, and I am not sure that I could get a deep enough coverage of the subject to do that. I don’t really feel like it has to be the definitive source...(read more)

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• Recommendations for books and training resources covering for Design for Programmers

  - by Jon Hopkins

  Off the back of one of the answers to this question (currently the second highest scoring), it made me think, what's the best way to get developers up to speed on good basic design principals. I'm not talking about making them into graphic designers but some developers almost take pride in ugly UIs, seeing them as unimportant next to the functionality. What primarily interested in are the graphic design elements rather than the usability aspects which is pretty well covered by books such as Don't Make Me Think. Use of white space, emphasis, font selection and a million other things I'm probably not even aware of. I know people are often seen as artistic or not artistic but surely the basics can be taught and someone has written a book covering this?

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• Is this proper OO design for C++?

  - by user121917

  I recently took a software processes course and this is my first time attempting OO design on my own. I am trying to follow OO design principles and C++ conventions. I attempted and gave up on MVC for this application, but I am trying to "decouple" my classes such that they can be easily unit-tested and so that I can easily change the GUI library used and/or the target OS. At this time, I have finished designing classes but have not yet started implementing methods. The function of the software is to log all packets sent and received, and display them on the screen (like WireShark, but for one local process only). The software accomplishes this by hooking the send() and recv() functions in winsock32.dll, or some other pair of analogous functions depending on what the intended Target is. The hooks add packets to SendPacketList/RecvPacketList. The GuiLogic class starts a thread which checks for new packets. When new packets are found, it utilizes the PacketFilter class to determine the formatting for the new packet, and then sends it to MainWindow, a native win32 window (with intent to later port to Qt).1 Full size image of UML class diagram Here are my classes in skeleton/header form (this is my actual code): class PacketModel { protected: std::vector<byte> data; int id; public: PacketModel(); PacketModel(byte* data, unsigned int size); PacketModel(int id, byte* data, unsigned int size); int GetLen(); bool IsValid(); //len >= sizeof(opcode_t) opcode_t GetOpcode(); byte* GetData(); //returns &(data[0]) bool GetData(byte* outdata, int maxlen); void SetData(byte* pdata, int len); int GetId(); void SetId(int id); bool ParseData(char* instr); bool StringRepr(char* outstr); byte& operator[] (const int index); }; class SendPacket : public PacketModel { protected: byte* returnAddy; public: byte* GetReturnAddy(); void SetReturnAddy(byte* addy); }; class RecvPacket : public PacketModel { protected: byte* callAddy; public: byte* GetCallAddy(); void SetCallAddy(byte* addy); }; //problem: packets may be added to list at any time by any number of threads //solution: critical section associated with each packet list class Synch { public: void Enter(); void Leave(); }; template<class PacketType> class PacketList { private: static const int MAX_STORED_PACKETS = 1000; public: static const int DEFAULT_SHOWN_PACKETS = 100; private: vector<PacketType> list; Synch synch; //wrapper for critical section public: void AddPacket(PacketType* packet); PacketType* GetPacket(int id); int TotalPackets(); }; class SendPacketList : PacketList<SendPacket> { }; class RecvPacketList : PacketList<RecvPacket> { }; class Target //one socket { bool Send(SendPacket* packet); bool Inject(RecvPacket* packet); bool InitSendHook(SendPacketList* sendList); bool InitRecvHook(RecvPacketList* recvList); }; class FilterModel { private: opcode_t opcode; int colorID; bool bFilter; char name[41]; }; class FilterFile { private: FilterModel filter; public: void Save(); void Load(); FilterModel* GetFilter(opcode_t opcode); }; class PacketFilter { private: FilterFile filters; public: bool IsFiltered(opcode_t opcode); bool GetName(opcode_t opcode, char* namestr); //return false if name does not exist COLORREF GetColor(opcode_t opcode); //return default color if no custom color }; class GuiLogic { private: SendPacketList sendList; RecvPacketList recvList; PacketFilter packetFilter; void GetPacketRepr(PacketModel* packet); void ReadNew(); void AddToWindow(); public: void Refresh(); //called from thread void GetPacketInfo(int id); //called from MainWindow }; I'm looking for a general review of my OO design, use of UML, and use of C++ features. I especially just want to know if I'm doing anything considerably wrong. From what I've read, design review is on-topic for this site (and off-topic for the Code Review site). Any sort of feedback is greatly appreciated. Thanks for reading this.

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• Design Pattern for Complex Data Modeling

  - by Aaron Hayman

  I'm developing a program that has a SQL database as a backing store. As a very broad description, the program itself allows a user to generate records in any number of user-defined tables and make connections between them. As for specs: Any record generated must be able to be connected to any other record in any other user table (excluding itself...the record, not the table). These "connections" are directional, and the list of connections a record has is user ordered. Moreover, a record must "know" of connections made from it to others as well as connections made to it from others. The connections are kind of the point of this program, so there is a strong possibility that the number of connections made is very high, especially if the user is using the software as intended. A record's field can also include aggregate information from it's connections (like obtaining average, sum, etc) that must be updated on change from another record it's connected to. To conserve memory, only relevant information must be loaded at any one time (can't load the entire database in memory at load and go from there). I cannot assume the backing store is local. Right now it is, but eventually this program will include syncing to a remote db. Neither the user tables, connections or records are known at design time as they are user generated. I've spent a lot of time trying to figure out how to design the backing store and the object model to best fit these specs. In my first design attempt on this, I had one object managing all a table's records and connections. I attempted this first because it kept the memory footprint smaller (records and connections were simple dicts), but maintaining aggregate and link information between tables became....onerous (ie...a huge spaghettified mess). Tracing dependencies using this method almost became impossible. Instead, I've settled on a distributed graph model where each record and connection is 'aware' of what's around it by managing it own data and connections to other records. Doing this increases my memory footprint but also let me create a faulting system so connections/records aren't loaded into memory until they're needed. It's also much easier to code: trace dependencies, eliminate cycling recursive updates, etc. My biggest problem is storing/loading the connections. I'm not happy with any of my current solutions/ideas so I wanted to ask and see if anybody else has any ideas of how this should be structured. Connections are fairly simple. They contain: fromRecordID, fromTableID, fromRecordOrder, toRecordID, toTableID, toRecordOrder. Here's what I've come up with so far: Store all the connections in one big table. If I do this, either I load all connections at once (one big db call) or make a call every time a user table is loaded. The big issue here: the size of the connections table has the potential to be huge, and I'm afraid it would slow things down. Store in separate tables all the outgoing connections for each user table. This is probably the worst idea I've had. Now my connections are 'spread out' over multiple tables (one for each user table), which means I have to make a separate DB called to each table (or make a huge join) just to find all the incoming connections for a particular user table. I've avoided making "one big ass table", but I'm not sure the cost is worth it. Store in separate tables all outgoing AND incoming connections for each user table (using a flag to distinguish between incoming vs outgoing). This is the idea I'm leaning towards, but it will essentially double the total DB storage for all the connections (as each connection will be stored in two tables). It also means I have to make sure connection information is kept in sync in both places. This is obviously not ideal but it does mean that when I load a user table, I only need to load one 'connection' table and have all the information I need. This also presents a separate problem, that of connection object creation. Since each user table has a list of all connections, there are two opportunities for a connection object to be made. However, connections objects (designed to facilitate communication between records) should only be created once. This means I'll have to devise a common caching/factory object to make sure only one connection object is made per connection. Does anybody have any ideas of a better way to do this? Once I've committed to a particular design pattern I'm pretty much stuck with it, so I want to make sure I've come up with the best one possible.

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• add schema to path in postgresql

  - by veilig

  I'm the process of moving applications over from all in the public schema to each having their own schema. for each application, I have a small script that will create the schema and then create the tables,functions,etc... to that schema. Is there anyway to automatically add a newly created schema to the search_path? Currently, the only way I see is to find the users current path SHOW search_path; and then add the new schema to it SET search_path to xxx,yyy,zzz; I would like some way to just say, append schema zzz to the users_search path. is this possible?

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• Design Application to "Actively" Invite Users (pretend they have privileges)

  - by user3086451

  I am designing an application where users message one another privately, and may send messages to any Entity in the database (an Entity may not have a user account yet, it is a professional database). I am not sure how to best design the database and the API to allow messaging unregistered users. The application should remain secure, and data only accessed by those with correct permissions. Messages sent to persons without user accounts serve as an invitation. The invited person should be able to view the message, act on it, and complete the user registration upon receiving an InviteMessage. In simple terms, I have: User misc user fields (email, pw, dateJoined) Entity (large professional dataset): personalDetails... user->User (may be null) UserMessage: sender->User recipient->User dateCreated messageContent, other fields..... InviteMessage: sender->User recipient->Entity expiringUrl inviteeEmail inviteePhone I plan to alert the user when selecting a recipient that is not registered yet, and inform that he may send the message as an invitation by providing email, phone where we can send the invitation. Invitations will have a unique, one-time-use URL, e.g. uuid.uuid4(). When accessed, the invitee will see the InviteMessage and details about completing his/her registration profile. When registration is complete, InviteMessage details to a new instance of UserMessage (to not lose their data), and assign it to the newly created User. The ability to interact with and invite persons who do not yet have accounts is a key feature of the application, and it seems better to separate the invitation from the private, app messages (easier to keep functionality separate, better if data model changes). Is this a reasonable, good design? If not, what would you suggest? Do you have any improvements? Am I correct to choose to create a separate endpoint for creating invitations via the API?

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• Recommened design pattern to handle multiple compression algorithms for a class hierarchy

  - by sgorozco

  For all you OOD experts. What would be the recommended way to model the following scenario? I have a certain class hierarchy similar to the following one: class Base { ... } class Derived1 : Base { ... } class Derived2 : Base { ... } ... Next, I would like to implement different compression/decompression engines for this hierarchy. (I already have code for several strategies that best handle different cases, like file compression, network stream compression, legacy system compression, etc.) I would like the compression strategy to be pluggable and chosen at runtime, however I'm not sure how to handle the class hierarchy. Currently I have a tighly-coupled design that looks like this: interface ICompressor { byte[] Compress(Base instance); } class Strategy1Compressor : ICompressor { byte[] Compress(Base instance) { // Common compression guts for Base class ... // if( instance is Derived1 ) { // Compression guts for Derived1 class } if( instance is Derived2 ) { // Compression guts for Derived2 class } // Additional compression logic to handle other class derivations ... } } As it is, whenever I add a new derived class inheriting from Base, I would have to modify all compression strategies to take into account this new class. Is there a design pattern that allows me to decouple this, and allow me to easily introduce more classes to the Base hierarchy and/or additional compression strategies?

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• Should universities put more emphasis on teaching their students about design patterns?

  - by gablin

  While I've heard about design patterns being mentioned in a few courses at uni, I know of only a single course which actually teaches design patterns. In almost all other areas (algorithms, parallelism, architecture, dynamic languages, paradigms, etc), there are several, often a basic course and an advanced course. Should universities put more emphasis about teaching their students about design patterns and provide more courses in design patters? Are lack of knowledge about design patterns common in just-graduated junior developers?

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• Which design pattern to use when using ORM?

  - by RPK

  I am writing a small ASP.NET Web Forms application. In my solution explorer, I added various class library projects to define layers, viz: Model Repository Presentation WebUI Someone suggested me that this layered approach is not of much sense if I am using ORM tool like PetaPoco, which itself takes care of separation of data access layer. I want to use PetaPoco micro-ORM and want to know which design pattern is suitable with ORM tools. Do I still need several class library projects to separate the concerns?

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• Good Video Game User Interface Design Books/Websites?

  - by Tucker Morgan

  I having been programming games for some time, but while my teachers say that my code is good and advanced, my friends say that the interface is hard to understand and not the easiest to navigate. I want to learn how to design good user interfaces so that I can program better games, and people will have a easier time getting around. Does anyone know of any good books or websites about designing video game interfaces?

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• Explanation needed, for “Ask, don't tell” approach?

  - by the_naive

  I'm taking a course on design patterns in software engineering and here I'm trying to understand the good and the bad way of design relating to "coupling" and "cohesion". I could not understand the concept described in the following image. The example of code shown in the image is ambiguous to me, so I can't quite clearly get what exactly "Ask, don't tell!" approach mean. Could you please explain?

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