Database System Concepts and Architecture [TOC] Data Abstraction --> !!!View!!! A major purpose of a DBS: providing abstract view of data Data abstraction at several levels DBS: retrieve data efficiently [new view means new index -> quick search] Need for efficiency has……
[toc] 基本概念 Data is a collection of symbols recorded things, it represent some meaning (information) only if it is interpreted. Information: factors: "meaning", "humans", "assign to", "data" concept: Information is a concept / notion that holds only if there……
Network Flow Flow network. Abstraction for material flowing through the edges. G = (V, E) = directed graph, no parallel edges. 【简单图】 Two distinguished nodes: s = source, t = sink. c(e) = capacity of edge e. D……
Dynamic Programming Dynamic programming: Break up a problem into a series of overlapping sub-problems, and build up solutions to larger and larger sub-problems. Weighted Interval Scheduling Weighted interval scheduling problem. Job j starts at $s_j$, finishes at $f_j$, and has weight or……