"How does it connect to my WMS?" is usually the first technical question in any automated storage and retrieval system (ASRS) evaluation, and it deserves a better answer than "there's an API." Integration is where automation projects succeed or stall, and the buyers who understand what's actually being connected make better vendor decisions and smoother go-lives.
The short answer: your WMS stays the system of record for inventory and orders, the ASRS runs its own control software for everything happening inside the structure, and the two exchange a defined set of messages through an integration layer. The longer answer is worth understanding in three parts: the software stack, the data that moves between systems, and the work required before anything connects.
The Warehouse Software Stack: WMS, WCS, and WES
Three software layers show up in almost every automated facility, and the names get confused often enough to cause real procurement mistakes.
Warehouse Management System (WMS). The planning layer. It owns inventory records, order management, receiving, and overall warehouse visibility. A WMS decides what needs to happen, typically releasing work in waves or batches, but it doesn't control machines.
Warehouse Control System (WCS). The machine layer. A WCS directly controls automated equipment (conveyors, sorters, ASRS, robots) and synchronizes physical movements in real time. It executes what the layers above it decide.
Warehouse Execution System (WES). The orchestration layer between the two. A WES takes released order data and decides when and how to act on it based on live floor conditions, then hands instructions to the equipment control layer.
In practice: the WMS releases order data, the WES sequences it against real-time conditions, and the WCS carries the instructions to the machines. Smaller operations often run just WMS plus the ASRS vendor's control software. Larger ones layer in a WES when multiple automation systems need coordinating.
Where the ASRS Sits in That Stack
A modern ASRS ships with its own control software, and that software does more than move robots. Attabotics' system, for example, includes proprietary software that operates the entire Storage System: it manages robot movement, order fulfillment, sequencing, sortation, and conveyance inside the Cubic Storage Structure, running the robots in 90-second waves.
That matters for integration scope. Your WMS doesn't need to know which robot fetches which bin or in what order. It needs to send orders and receive confirmations and inventory updates. The choreography inside the structure is the ASRS software's job, which keeps the integration surface between the two systems small and stable.
Attabotics connects that software to host systems through an integration API built for WMS connectivity. Per the company's published FAQ, the system works with existing software regardless of API: a communications layer can talk to any host system as long as the interface is specified. The software also supports customizable order processing for specific business rules, and optional continuous 5G wireless communication to the robots.
The Three Connections That Make Up "Integration"
Treating integration as a single connector is how projects get underscoped. It's more accurate to think of three distinct connections:
1. The machine connection. How the ASRS control software talks to its own hardware, and how the system connects to surrounding equipment like conveyors or pack stations. This is largely the vendor's responsibility, but it defines what's possible at the boundaries, so it belongs in the evaluation conversation.
2. The data connection. The message traffic between the WMS and the ASRS. The core flows are consistent across the industry: orders and item master data travel down from the WMS; pick confirmations, inventory adjustments, and exceptions travel back up. Every time an item enters or leaves the ASRS, the system updates its own inventory database and sends that update to the host, keeping the two systems synchronized in near real time.
3. The workflow connection. The operational logic that decides how the automated process and your human processes fit together. Which orders route to the ASRS versus manual picking? How are partial orders consolidated? What happens to exceptions? This is the layer that determines whether the system fits your operation or forces your operation to fit the system, and it's where configurable business rules earn their keep.
Vendors quote the data connection. Projects live or die on the workflow connection.
What Data Actually Flows Between WMS and ASRS
A typical message set between a WMS and an ASRS covers:
| Direction | Message | Purpose |
|---|---|---|
| WMS → ASRS | Item master data | Dimensions, weights, storage rules for each SKU |
| WMS → ASRS | Inbound/putaway notices | What's arriving for induction into the system |
| WMS → ASRS | Order releases | Order lines the ASRS should fulfill |
| ASRS → WMS | Pick confirmations | Line-level confirmation as work completes |
| ASRS → WMS | Inventory adjustments | Real-time stock updates as items enter and leave |
| ASRS → WMS | Exceptions | Shorts, damaged items, cycle count discrepancies |
The WMS remains the system of record; the ASRS control layer depends on receiving accurate, current data from it. That dependency is why the preparation work below matters more than the connector technology.
What to Prepare Before Integration Starts
Integration problems are usually data problems discovered late. Industry best practice, consistent across integrators and software vendors, comes down to four preparation steps:
- Audit your master data. Item dimensions, weights, packaging hierarchies, and storage rules need to be accurate before installation, because the ASRS makes physical decisions based on them. An item master that's 95% right means 5% of your SKUs jam, misroute, or get rejected at induction.
- Confirm the system of record. Decide explicitly which system owns inventory truth, and at what points the two systems reconcile. Ambiguity here becomes phantom inventory later.
- Map the message set. Define which messages your WMS sends, which transactions the ASRS reports back, and how each side handles the other's exceptions. Get this in writing during vendor evaluation, not during implementation.
- Test against your real workflows. Test scenarios should cover your actual order profile, including the awkward cases: partial lines, returns, cycle counts, and peak-volume sequencing.
Ask every ASRS vendor the same two questions: which WMS platforms have you integrated with before, and what happens when my WMS sends something your system doesn't expect? The quality of the second answer tells you most of what you need to know.
Proof Point: Integrating Alongside a Legacy Operation
Integration doesn't only mean connecting software. Gordon Food Service's Calgary distribution center integrated Attabotics' 3D robotic system directly with its existing manual picking operations, running the automated system in tandem with legacy processes rather than replacing them at once. That deployment pattern, automation absorbing volume while established workflows continue, is what a well-scoped workflow connection makes possible, and the partnership has run continuously since 2018.
FAQ
Do I need to replace my WMS to install an ASRS?
No. An ASRS is designed to work under your existing WMS, which stays the system of record for inventory and orders. Attabotics, for example, states its communications layer can work with any host system regardless of API, as long as the interface is specified.
What's the difference between a WMS and a WCS?
A WMS is the planning layer: it manages inventory, orders, and warehouse processes, and decides what needs to happen. A WCS is the machine layer: it directly controls automated equipment in real time and executes the work. An ASRS arrives with its own control software filling the WCS role for the equipment it runs.
How does inventory stay accurate between the WMS and the ASRS?
Through continuous message exchange. Each time an item enters or leaves the ASRS, the system updates its own database and sends the adjustment to the WMS, so both systems reflect the same stock position in near real time.
What causes most ASRS integration problems?
Data quality, more than connectivity. Inaccurate item dimensions, weights, or packaging data cause physical failures at induction and picking, which is why auditing master data before installation is the most consistently recommended preparation step.
Can an ASRS handle order logic specific to my business?
The better systems can. Attabotics' software supports customizable order processing for specific business rules, and its workstations switch between picking, decanting, cycle counts, and kitting by mode. Confirm the specific rules you need during vendor evaluation rather than assuming.
Conclusion
ASRS-WMS integration is a defined, well-trodden path, not a research project. Your WMS keeps its job, the ASRS control software keeps its own, and a specified message set connects the two. The projects that go smoothly are the ones that treat integration as three connections (machine, data, workflow), clean their master data before installation, and pressure-test the workflow logic against real order profiles. The projects that struggle are the ones that bought a connector and assumed the rest would follow. Know which project you're running before you sign.
Sources
- Made4net — WMS vs. WCS vs. WES Explained — software layer definitions and how they divide planning, orchestration, and machine control
- Modula — WES vs. WMS vs. WCS: Differences and How They Work Together — stack roles and the release/orchestrate/execute flow
- MHI Blog — Understanding ASRS Software Integration — message mapping between WMS and ASRS, inventory update flow
- OPEX — Bridging Legacy Systems with Automation — API connections to legacy systems, data mapping before deployment
- ASC Software — Automated Storage and Retrieval Systems Guide — WMS as system of record, master data audit recommendation
- Attabotics — Warehouse Automation Technology — Attabotics Software capabilities, integration API, communications-layer FAQ, 5G option, workstation modes
- Attabotics — Gordon Food Service Calgary Case Study (PDF) — integration alongside legacy manual picking operations since 2018
