Some exhibit/booth areas are staffed by knowledgeable people who are happy to answer questions, chat and/or listen to ideas for using or improving their products.
> no base point to start a conversation
How about the topic of the talk?
If you ask a question during Q&A, others may be interested and approach you to follow up.
> like a dating site except with no bio
Conference speakers typically have public bios and photos, which helps with hallway recognition. Those who are open to talking can often be found in a small group, which can be joined via topical comment/question.
But usually such very big shows happen somewhere in the USA/UK/west Europe etc. And pricey. What I've seen in my country were usually a conferences structured like a series of talks with breaks. If conference is big then 2 or 3 treks in parallel in different room. In this case there is only one point of interest - the presenter, and maybe one or two previous or next presenters. It's not a problem to recognize presenter, a problem is talk to him/her longer than a single carefully prepared question and answer, because there are like 20 other people around all trying to talk to him/her.