A data structure describing how the properties of a particular section differ from a Word-defined standard SEP. As in the PAPX, the differences between the SEP for a section and the standard SEP are encoded as list of sprms that describe how the standard SEP can be transformed into the section's SEP. By applying a SEPX's sprms to the standard SEP, it is possible to reconstitute the SEP for that section.
The PLCFSED, a data structure stored in a Word file, records the locations of all SEPXs stored in a Word file. The array of CPs in the plcfsed records the boundaries of sections in the Word document . The second array in the plcf, an array of SEDs (SEction Descriptors), is in 1-to-1 correspondence to the array of CPs. Each SED stores the beginning FC of the SEPX that records the properties for a section. If the FC stored in a SED is -1, the section properties of the section are exactly equal to the standard section properties.
The SEP for a particular section may be constructed if a CP of a character in that section is known. First search the array of CPs in the PLCSED for the index of the largest CP that is less than or equal to the CP of the character. Use this index to locate the SED in the plcfsed which describes the section. The FC stored in the SED is the offset from the beginning of the Word file at which the SEPX is stored. If the stored FC is equal to 0xFFFFFFFF, then the SEP for the section is exactly equal to the standard SEP (see SEP structure definition) Otherwise, read the SEPX into memory and create a copy of the standard SEP. Finally, apply the sprms stored in the SEPX to the standard SEP to produce the SEP for a section.