user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: acm sig proceeding is a conference event of what? 
Knowledge Triplets: ACMGIS 2012, base.giscience.giscience_event.has_keynote_speaker, Samuel Madden
ACMGIS 2012, conferences.conference.series, ACM SIGSPATIAL
ACMGIS 2012, time.event.start_date, 2012-11-06
Redondo Beach, conferences.conference_venue.conferences, ACMGIS 2012
Geographic information science, conferences.conference_subject.specific_conferences_about_this, ACMGIS 2012
ACM SIGSPATIAL, time.recurring_event.instances, ACMGIS 2012
ACMGIS 2012, base.giscience.giscience_event.has_keynote_speaker, Brian McClendon
ACMGIS 2012, conferences.conference.venue, Redondo Beach
ACMGIS 2012, time.event.instance_of_recurring_event, ACM SIGSPATIAL
ACMGIS 2012, time.event.end_date, 2012-11-09
ACM SIG Proceeding, conferences.conference_proceedings.conference, ACMGIS 2012
ACMGIS 2012, conferences.conference.proceedings, ACM SIG Proceeding
ACMGIS 2012, base.giscience.giscience_event.has_submission_deadline, 2012-06-25
ACMGIS 2012, time.event.locations, Redondo Beach
ACM SIGSPATIAL, conferences.conference_series.conference, ACMGIS 2012
Redondo Beach, location.location.events, ACMGIS 2012
ACMGIS 2012, conferences.conference.focus, Geographic information science

Answer: ACMGIS 2012