BIG DATA IS A GENERIC TERM THAT INVOLVES THE STORING AND PROCESSING OF A LARGE AMOUNT OF DATA. THIS LARGE AMOUNT OF DATA HAS BEEN PROMOTED BY TECHNOLOGIES SUCH AS MOBILE APPLICATIONS, INTERNET OF THINGS (IOT), AND GEOGRAPHIC INFORMATION SYSTEMS (GIS). AN EXAMPLE OF GIS IS A SPATIO-TEMPORAL DATABASE (STDB). A COMPLEX PROBLEM TO ADDRESS IN TERMS OF PROCESSING TIME IS PATTERN SEARCHING ON STDB. NOWADAYS, HIGH INFORMATION PROCESSING CAPACITY IS AVAILABLE EVERYWHERE. NEVERTHELESS, THE PATTERN SEARCHING PROBLEM ON STDB USING TRADITIONAL DATA MINING TECHNIQUES IS COMPLEX BECAUSE THE DATA INCORPORATE THE TEMPORAL ASPECT. TRADITIONAL TECHNIQUES OF PATTERN SEARCHING, SUCH AS TIME SERIES, DO NOT INCORPORATE THE SPATIAL ASPECT. FOR THIS REASON, TRADITIONAL ALGORITHMS BASED ON ASSOCIATION RULES MUST BE ADAPTED TO FIND THESE PATTERNS. MOST OF THE ALGORITHMS TAKE EXPONENTIAL PROCESSING TIMES. IN THIS PAPER, A NEW EFFICIENT ALGORITHM (NAMED MINUS-F1) TO LOOK FOR PERIODIC PATTERNS ON STDB IS PRESENTED. OUR ALGORITHM IS COMPARED WITH APRIORI, MAX-SUBPATTERN, AND PPA ALGORITHMS ON SYNTHETIC AND REAL STDB. ADDITIONALLY, THE COMPUTATIONAL COMPLEXITIES FOR EACH ALGORITHM IN THE WORST CASES ARE PRESENTED. EMPIRICAL RESULTS SHOW THAT MINUS-F1 IS NOT ONLY MORE EFFICIENT THAN APRIORI, MAX-SUBPATTERN, AND PAA, BUT ALSO IT PRESENTS A POLYNOMIAL BEHAVIOR.

IN THIS ARTICLE WE PRESENT PRELIMINARY RESULTS OF A PROJECT IMPLEMENTED AT THE UNIVERSIDAD DEL BÍO-BÍO (UBB), CONCEPCIÓN CAMPUS, THAT SEEKS TO CONTRIBUTE TO INCREASING THE PERCEPTION OF SECURITY AMONG USERS, BY USING INFORMATION AND COMMUNICATION TECHNOLOGIES (ICTS). CURRENTLY, COMMUNITY MEMBERS OF THE CONCEPCION CAMPUS AT UBB SHOW DIFFERENT PERCEPTIONS OF INSECURITY. INITIALLY, WE PERFORM A DIAGNOSIS TO KNOW WHAT ARE THE INSECURITY PROBLEMS THAT AFFECT THE COMMUNITY, AND THE EFFECTS OF INSECURITY ON THE WELL-BEING OF THE COMMUNITY OF THE CONCEPCIÓN CAMPUS. IN THIS WAY, WE ESTABLISH THE MAIN PROBLEMS AROUND SECURITY AND EVALUATE DIFFERENT WAYS IN WHICH THE USE OF ICTS CONTRIBUTES TO IMPROVE THE INSECURITY PERCEPTION. THIS ARTICLE REPORTS A MOBILE APPLICATION PROTOTYPE, THAT ALLOWS ALERTING OF POSSIBLE UNSAFE EVENTS, TO BE USED WITHIN THE CONCEPCIÓN CAMPUS. THIS APPLICATION ALSO PERMITS TO GENERATE REPORTS OF SECURITY PROBLEMS THAT ARE PERCEIVED AT THE CAMPUS, WHICH ALLOW BOTH APPLICATION USERS AND UNIVERSITY MANAGERS TO ACQUIRE INFORMATION ON THE UNIVERSITY ENVIRONMENT IN TERMS OF SECURITY.

WE PRESENT EFFICIENT ALGORITHMS TO COMPUTE SIMPLE AND COMPLEX MAP ALGEBRA OPERATIONS OVER RASTER DATA STORED IN MAIN MEMORY, USING THE K2-ACC COMPACT DATA STRUCTURE. RASTER DATA CORRESPOND TO NUMERICAL DATA THAT REPRESENT ATTRIBUTES OF SPATIAL OBJECTS, SUCH AS TEMPERATURE OR ELEVATION MEASURES. COMPACT DATA STRUCTURES ALLOW EFFICIENT DATA STORAGE IN MAIN MEMORY AND QUERY THEM IN THEIR COMPRESSED FORM. A K2-ACC IS A SET OF K2-TREES, ONE FOR EVERY DISTINCT NUMERIC VALUE IN THE RASTER MATRIX. WE DEMONSTRATE THAT MAP ALGEBRA OPERATIONS CAN BE COMPUTED EFFICIENTLY USING THIS COMPACT DATA STRUCTURE. IN FACT, SOME MAP ALGEBRA OPERATIONS PERFORM OVER FIVE ORDERS OF MAGNITUDE FASTER COMPARED WITH ALGORITHMS WORKING OVER UNCOMPRESSED DATASETS.

ABSTRACT?WE REPORT EFFICIENT ALGORITHMS TO COMPUTE THE MAP ALGEBRA OPERATIONS THRESHOLDING, SUM/MULTIPLICATION BY A SCALAR, POINT-WISE SUM, AND ZONAL SUM OVER RASTER DATA STORED IN MAIN MEMORY ON THE COMPACT DATA STRUCTURE K2-RASTER. RASTER DATA CORRESPOND TO NUMERICAL DATA, SUCH AS TEMPERATURE AND ELEVATION MEASURES RELATED TO SPATIAL OBJECTS LIKE CITIES, COUNTRIES, AMONG OTHERS. IN GENERAL, SPATIAL DATA CAN BE VERY LARGE, AND THEREFORE, THEY CAN BE STORED IN MAIN MEMORY IN COMPACT DATA STRUCTURES, WHICH ALLOW EFFICIENT DATA STORAGE AND QUERY THE DATA IN THEIR COMPRESSED FORM. ACCORDING TO THE LITERATURE, THE K2-RASTER IS THE BEST COMPACT DATA STRUCTURE TO HANDLE RASTER DATA, AND IT CORRESPONDS TO A K2 -TREE THAT STORES THE MAXIMUM AND MINIMUM VALUES FOR EACH INTERNAL NODE. WE THEORETICALLY SHOW THAT MAP ALGEBRA OPERATIONS CAN BE COMPUTED EFFICIENTLY USING A K2-RASTER COMPACT DATA STRUCTURE. IN FACT, MOST OF THE MAP ALGEBRA OPERATIONS HAVE A THEORETICAL EXPECTED TIME EQUIVALENT TO THE TIME OF TRAVERSING THE STRUCTURE.