- What is a Change Only Update (COU) supply of the AddressBase products?
A change only update (COU) supply of data contains records or files that have changed between product refreshes to a customer.
COU data enables a user to identify three types of change:
1) Inserts (CHANGE_TYPE ‘I’) are objects that have been newly inserted into your area of interest since the last product refresh.
2) Deletes (CHANGE_TYPE ‘D’) are objects that have ceased to exist in your area of interest since the last product refresh.
3) Updates (CHANGE_TYPE ‘U’) are objects that have been updated in your area of interest since the last product refresh.
- Will the COU change type be the same for an address that has been updated in all of the AddressBase products?
Not necessarily. In the main, if an address that exists in all 3 products has changed the COU will be reflected consistently (where the change is within each respective technical specification). However, because AddressBase Premium contains provisional and historic records it is possible that COU change types will differ between products.
For example, if a house is under construction, the address of this house (when known) may appear in AddressBase Premium as a ‘provisional address’. This would be reflected as a COU change type of ‘I’ because it is being inserted into this product for the first time. This address would not appear in the COU for AddressBase or AddressBase Plus because these products only contain the current ‘approved’ addresses. When the construction of the house is completed and the status of the address is set to ‘approved’ it is only then that the COU for AddressBase and AddressBase Plus will capture this change as ‘I’. This address status change would be reflected as a ‘U’ in AddressBase Premium because an existing record is being updated.
Likewise, if an address is demolished in the real world there is no longer a requirement to manage the address as the current address. Therefore, in AddressBase and AddressBase Plus this record will have a change type of ‘D’ and will be deleted from your data holdings when applied. In AddressBase Premium however, the change type for this record will be ‘U’ because a status attribute is updated to reflect that it is a historic record.
- What benefit will I receive if I take a COU refresh of the product over a full supply refresh?
The benefit of receiving your product as a COU supply is that data volumes are smaller therefore it will significantly reduce the amount of time required to process each product refresh of the data when compared to the time taken to process a full supply. This means that the most up to date AddressBase products content will be available to you quicker.
COU supply is most effective when applied every time that the product is refreshed. For example, AddressBase products are refreshed every six weeks (as full supply and COU). Therefore to ensure that your data holdings are complete and consistent with the full supply, you should request and apply COU for your area of interest every six weeks.
- What does ‘base-lining my data’ mean?
‘Base-lining’ is preparing your data holdings with the most up-to-date full supply of the product before applying change only update for the first time.
If you have previously been supplied your product data as a full supply it is important that before you apply a COU to your data holdings you ensure that your data holdings are up-to-date. For example, if you intend to apply COU for the first time using Epoch 17 COU, you must ensure that the Epoch 16 Full Supply is loaded as a baseline in your data holdings. If this isn’t the case and you apply Epoch 17 COU to Epoch 15 Full Supply you may lose some important changes and corrupt your data holdings.
- How will AddressBase products Change Only Update (COU) files be supplied?
The data is delivered in one of two methods:
- Non geographic chunks (containing up to 1 million changes)
- Geographic chunks (5km x 5km ‘tiles’). This option only applies to PSMA customers.
Customers may request updates of the latest changes in their order area at any time using the Ordnance Survey online service. Customers can assign a regular date for receipt of COU. These will then be sent automatically on the required media or placed on the file transfer protocol (FTP) server for collection (if under 2GB). Public sector users can download their geographic chunked COU in the same way that they download the full supply geographic chunks.
- Are there any differences between CSV and GML COU?
The addresses contained in the COU for the CSV and GML product formats are exactly the same. However, because the data is structured differently, there are subtle differences in the way feature lifecycles are captured in AddressBase Premium.
AddressBase Premium CSV contains lifecycle information (e.g. last_update_date) for all of the record identifiers (excluding header, trailer and metadata). This granular view of change brings with it a real advantage if your business has a requirement to understand the nature of the change. For example, if you have an interest in seeing how many ‘Commercial’ properties have been updated to ‘Residential’ you can extract this information out from your data holdings using date ranges.
AddressBase Premium GML contains lifecycle information for the BLPU member and the Street member. The BLPU member contains the following address elements: LPI, Classification, Delivery Point Address, Application Cross Reference, Organisation and Successor. The Street member contains the Street and Street Descriptor elements. By structuring the data within these 2 members the user will benefit by being able to load an address into many commonly used applications without the need for translation. This means the data can be used for more than just a transfer format and be implemented in its raw format.
- AS I use AddressBase product under a Public Sector Agreement licence, is COU available as tiles?
Yes. Public Sector users can order COU as geographic chunks (5km x 5km tiles). This data is currently available via the download service. COU supplied via this mechanism is ‘tile-based’ COU rather than ‘feature-based’. This means that if an address has changed, the entire tile will be supplied (including unchanged addresses that fall in that tile).
- What is a UPRN?
A Unique Property Reference Number (UPRN) is the persistent unique identifier that underpins the AddressBase products range.
Each record has a UPRN which provides a reference key to join related address records across different datasets.
Throughout its lifecycle, information on the address of a property can change. This may be due to a change of name, a sub-division or aggregation of an address within a building, change of use, such as from single occupancy to multiple occupancies or the eventual demolition of the property. All of these historic, alternative and provisional addresses are recorded against the same UPRN.
UPRNs are integers (numbers) that can be up to 12 digits in length; they can therefore be less than 12 digits long and do not require leading zeros. However some gazetteer database applications will pad UPRNs that are less than 12 digits with zeros.
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