What is a From-To List?

Connectivity is the engineering backbone of every operating facility. The drawings show it; the line list specifies it; the from-to list compresses it into a queryable table. For any team whose work depends on understanding how the plant is wired together — revamp scoping, MOC, MTO, integrity, LDAR — the from-to list is the document they reach for first.

From-to data sources

From-to information is derived from three sources, each with its own role:

• P&IDs and PFDs — lines are shown schematically connecting equipment and off-page connectors. The P&ID is the authoritative schematic source for every from-to entry.
• Isometrics — physical routing is documented spool by spool. The isometric confirms the from-to entry is consistent with how the line is actually built.
• Line list — the structured tabular record that carries the from-to columns alongside the rest of the line attributes.

Discrepancies between these three sources indicate either a documentation error or an undocumented field modification. On any operating facility, the gap between the from-to list on record and the from-to reality in the field is a leading indicator of audit and reliability findings.

From-to lists in brownfield work

On any modification to an existing facility, the from-to list is the first document engineers need to understand the scope. Which lines connect to the equipment being modified? Where do those lines go? What other systems are affected? Without accurate from-to data, scope definition relies entirely on field walkdowns and manual reading of drawings — weeks of engineering hours before any productive design work can begin.

From-to connectivity and the engineering knowledge graph

When from-to data is structured and contextualized across P&IDs, PFDs, isometrics, and line lists, it forms the connectivity backbone of the engineering knowledge graph — the logical map of how every line in the facility connects equipment to equipment and system to system. From a graph, the downstream questions become queries:

• Which lines feed this vessel, and what spec is each one built to?
• If we replace this exchanger, which upstream and downstream lines are inside the modification scope?
• For an LDAR survey, which components sit on lines connecting equipment in regulated service?
• For a turnaround MTO, which line numbers feed into this equipment cluster, and what is the aggregated material requirement?

Each of these is an intractable spreadsheet exercise on a static document set, and a single query against a contextualized from-to graph.