I am designing a bit of software that will integrate with our enterprise system using web services. We are dealing with work orders that are needed to maintain equipment. We have a bit of a disagreement in regards to the structure of the contract. There are two methods on my side, I would like a single work order class with all properties related to the work order in it. example (simplified)WO - class  Number - property  Description - property  WarrantyStatus - property  WarrantySettlementDate - property  LabourSteps<LabourStep>[] - list property  Children<WO>[] - list propertyOn their side, they want to create a work order class, but for each logical group of data,   they want to create another class to wrap the properties.  example (simplified)WO - class  WOHeader - class    Number - property    Description - property  Warranty - class    WarrantyStatus - property    WarrantySettlementDate - property  LabourSteps<LabourStep>[] - list property  Children<WO>[] - list propertyNow they will have approx 8 classes in the full definition that they want to create all with a few properties in each. This seems a bit over the top to me and has a bit of a code smell or anti pattern feel to it. For my example, I have two classes, WO and LabourStep. They have 4 classes for the same thing WO,WOHeader,Warranty,LabourStep. There will only ever be one WOHeader per WO and the same for Warranty.My one seems far simpler to manage changes (add a new property to WO and thats it), but is less human readable.On their side, The structure is a little more easier to read by a human, but it feel like its pushing a logical view onto the contract the doesn't really belong. And to add a new property potentially requires a modification to the WO and the creation of a new class if a new logical group was added. These extra classes are only there to group properties.What is the right way to go?======EDIT==========Frank - I completely agree with your thoughts and it is the way I approach my development. Except in this case, the third party monolithic enterprise system we are integrating with has been written in a very generic way to try and cater for as many businesses as possible. The data is spread across three tables in a one to one mapping with the majority in one table. There is barely any validation. There is no concept of a Warranty object/thing in that system. Its just 3 properties against a WO. All the web service will do is act like a data store, with the WO persisted as a whole. e.g. getWO() updateWO() createWO(). There will never be get/updateWarranty() methods. It's all just one blob of data to read/persist. On our side, we never use the result directly from web services even if they are our own. We convert them into proper models and then use those. To us a data contract is very different to a model. There is no business logic in the data contract, its purely a container to get data from one part of the system to another without closely coupling them. That means we can easily change to persist to a database instead of a web service and all its needs to do is match the interface of the web service. This also allows us to modify our own models which may even include results from multiple web services without having to worry about being restricted to or changing the format of the data contracts.So when I think in those terms, Having the data contracts split into WOHeader or WOWarranty classes just doesn't make any sense. It will never used in that way, not even by them. Its just there for a nice logical group of properties that mean nothing by themselves. A region block around those properties would have the same net effect. Labour steps and equipment details however, make a lot of sense to be in separate classes as they are separate entities and not just properties of work orders. 
Should we create classes just to group properties
design;web services