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Sending incremental updates

If the inventory management system is able to keep track of the changes made to the objects in the software it is possible to use incremental updates, allowing for real-time communication. Every time an advertiser needs a new object to be published the inventory management system should send an add mutation to DV. Then, if the object gets changed, for example if the asking price is lowered, a change mutation should be sent. And when the object has been sold, or if there is another reason why it should no longer be advertised, a delete mutation should be sent.
Change mutations need to include the complete object data, not just the data that has been changed. They are therefore very comparable to add mutations.

Sending incremental updates allows for a more real-time approach compared to sending data in bulk. It is however possible to save up several mutations before sending them as a group, if so desired.

Things to decide when using incremental updates:

  • Transfer method
    DV can accommodate several ways of sending mutations to DV, but the most common is using HTTP POST to our endpoint.
  • Data format
    DV accepts all common file formats that support structured data, like JSON and XML.
  • Character encoding
    DV supports the most common character encodings like UTF-8 (with or without BOM), ISO 8859-1, ISO 8859-15 and Windows-1252.
  • Queuing mechanism
    Processing mutations can take up to several seconds, depending on the amount of data. It is therefore advised to queue the mutations to be sent in the background instead of having the user wait.
    If desired it is possible to send mutations in parallel (max. 5 simultaneous requests). Keep in mind that sending multiple mutations for the same vehicle at the same time will have unwanted effects.
    It is also possible to send multiple mutations in the same request, even for different advertisers.

Response

Each request sent results in a response stating the result of the request. It is very much advised to check this result. If DV could not process the request the inventory management system should try again later.
The response is an XML message and is documented here: http://www.doorlinkenvoorraad.nl/xml/result.xsd (Dutch).
The response message can also include the status of the advertisements, as further described in II.4. Feedback.