# Lookup

Four reference works accompany you through market communication: the
check identifier on the message, the condition behind a
handbook line, the decision tree behind a rejection and the field in the
BO4E schema. All four are listed here per format version; choose the version
at the top right.

## Check identifiers

For every check identifier you see use case, rulebook and
communication direction, the field level down to the BO4E attribute with the
EDIFACT segment per field, the AHB lines with their conditions and the
processes in which the number occurs. If the application handbook lists several
use cases for one number, choose the one with the
communication direction of your message.

The numbers are listed on the left by message type, for example
[55001 in 202604](/en/schnittstellen/202604/pruefi/UTILMD/PI_55001) and
[in 202610](/en/schnittstellen/202610/pruefi/UTILMD/PI_55001). You can see which numbers a
format version carries without an interface of their own under
[Not listed](/en/schnittstellen/202604/pruefi/nicht-gefuehrt).

## AHB conditions

If a handbook line reads `Muss [704]`, look up condition 704 in
the AHB conditions of the message type. There is one page per format version and
EDIFACT format: [AHB conditions 202604](/en/referenz/202604/ahb-bedingungen/UTILMDS)
and [202610](/en/referenz/202610/ahb-bedingungen/UTILMDS) for UTILMD electricity; the
other formats (UTILMD gas, ORDERS, MSCONS, INVOIC and more) are listed on the left
in the tree.

## Decision trees

Result codes apply only within their decision tree. `A01` occurs in
<Kennzahl was="a01Baeume" /> of the <Kennzahl was="ebdGesamt" /> trees and
carries <Kennzahl was="a01Bedeutungen" /> different meanings there. Always read
a result code together with the tree it comes from, and do not take over
a meaning from another tree.

The decision trees are listed on the left by number, for example
[E_0003 in 202604](/en/referenz/202604/ebd/E_0003) and
[in 202610](/en/referenz/202610/ebd/E_0003).

## BO4E schemas

For every BO4E object you see the fields with type, mandatory flag and
description, as well as the check identifiers and events in which a field
is used. Many fields of an object occur in no message of this
format version: the BO4E schema is broader than market communication.

Starting points: [Business objects](/en/bo4e/202604/bo/Marktlokation),
[Components](/en/bo4e/202604/com/Adresse) and [Enums](/en/bo4e/202604/enum/Sparte).