What did Tim-Berners Lee mean with "HTTP also allows index search" in his paper "World wide web: The Information Univesrse"?

Question

For my work on the history of hypertext systems and the WWW I cam across one sentence on the development of HTTP which I don't understand and where I could not find any information about:
Page 55: (bold marking from me)

A new search and retrieve (SR) protocol, known as HTTP, was found to be necessary. Faster than FTP for document retrieval, HTTP also allows index search. HTTP is similar in implementation to the Internet protocols above and similar in functionality to the WAIS protocol. Some differences are discussed below.

The paper can be accessed here for free:

http://www.emeraldgrouppublishing.com/products/backfiles/pdf/backfiles_sample_5.pdf

Answer 1

It's probably a reference to the <ISINDEX> HTML element, which was like a <FORM> with a single input element, used for constructing queries like http://foo/bar?baz from the page http://foo/bar when baz was entered by the user. The purpose was for the page containing the <ISINDEX> element to serve as a "search engine" for some collection of documents that could be returned in response to the queries with parameter.

An explicit reference to search engines of the "search the contents of everything everywhere" type - and not as an idea but an implemented feature! - at this stage seems much less likely to me.

MDN has some historical links related to <ISINDEX> that may be of interest: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/isindex