2.1.850 Part 1 Section 18.15.2, stp (Strings in Subtopic)
a. The standard does not limit the length of the value of this element.
Excel restricts the value of this element to be at most 255 characters.
b. The standard describes 1 for stp for cube functions only.
In Office, a value of 0 for the first stp indicates that not all of the related cells with calling cube functions have been refreshed. For each Cube function, there shall be exactly one stp.
c. The standard makes no mention of an xml:space attribute.
Excel uses this attribute to specify, using the W3C space preservation rules, how white space should be handled for the element's contents; its allowed values are defined by the XML 1.0 specification.
d. The standard does not describe how stp relates to the RTD function.
In Office, for the RTD function, the first stp having a value of "" indicates that the RTP add-in is run on the local machine. Any other value for the stp indicates the server name. All subsequent stps indicate the topics of the RTD function.