The specification of the current Veloconnect version is available online here.
The documentation refers specifically to the XML schema reference for the XML schemas to be explained.

In progress:

• Click & Collect and Dropshipping
  • (Collect goods ordered online from a local retailer and have selected but out-of-stock goods delivered directly to your home by the supplier).

Current version:

• V. 1.6: 
  • Detailed sales data
    (Dealers can transmit article number, quantity, date of sale, and optionally price, zip code, sales channel and frame number for bicycles. Sales data is transmitted on a voluntary basis, among other things to improve the analysis of market demand and thus increase availability).
• V. 1.5:
  • Structured product data
    (Transmission of extended product data with attributes, optionally also via service providers such as Bidex, DST, e-vendo, ...).
• V. 1.4:
  • Transmission of dealer availabilities to manufacturer or service providers.
    (enables the display on the manufacturer's homepage or a marketplace of which shop in the vicinity has a desired product in stock).
• V. 1.3:
  • Document management
    (order confirmation, delivery note, invoice - with transfer of serial numbers)
• V. 1.1:
  • Article master data transfer (description, GTin/EAN, order no., prices)
  • Availability query
  • Orders (with immediate price and quantity comparison)

• pyveloedi, Python library.
• A description of the content of the extension to V. 1.3 can be found here.