String (computer science)

About: String (computer science) is a research topic. Over the lifetime, 19430 publications have been published within this topic receiving 333247 citations. The topic is also known as: str & s.

Non-literal textual search using fuzzy finite-state linear non-deterministic automata

Abstract: Method and system for selectively retrieving information contained in a stored document set using a metric-based or "fuzzy" finite-state non-deterministic automation. The system receives a generalized regular search expression from a user. The system then performs prematching during which it estimates a dissimilarity metric for each target string in the stored document set with respect to the search expression. The strings are then sorted by dissimilarity metric, with the best matches, i.e., the strings having the lowest dissimilarity metrics, first. The search expression is broken down into one or more segments. A linear fizzy finite-state non-deterministic automation is constructed (501) by matching each segment of the search expression with a corresponding set of states and transitions. The automation is initialized and then processes target strings read (502) from the sorted list, thereby generating a dissimilarity value for each target string. A dissimilarity value for each string is determined based upon penalties associated with one-to-one fuzzy character substitution, exchanged adjacent characters, one-to-many, many-to-one, and many-to-many character substitution, and other differences between the search expression and a target string read from storage.

Multiattribute hashing using Gray codes

Abstract: @)2 of this string decides the bucket that the record is stored. In this paper we propose to use Gray codes instead of binary codes, in order to map record signatures to buckets. In Gray codes, successive codewords differ in the value of exactly one bit position, thus, successive buckets hold records with similar record signatures. The proposed method achieves better clustering of similar records and avoids some of the (expensive) random disk accesses, replacing them with sequential ones. We develop a mathematical model, derive formulas giving the average performance of both methods and show that the proposed method achieves 0% - 50% relative savings over the binary codes. We also discuss how Gray codes could be applied to some retrieval methods designed for range queries, such as the grid file [Nievergelt84a] and the approach based on the so-called z-ordering [Orenstein84a].

Expressiveness of Streaming String Transducers

Abstract: Streaming string transducers define (partial) functions from input strings to output strings. A streaming string transducer makes a single pass through the input string and uses a finite set of variables that range over strings from the output alphabet. At every step, the transducer processes an input symbol, and updates all the variables in parallel using assignments whose right-hand-sides are concatenations of output symbols and variables with the restriction that a variable can be used at most once in a right-hand-side expression. It has been shown that streaming string transducers operating on strings over infinite data domains are of interest in algorithmic verification of list-processing programs, as they lead to Pspace decision procedures for checking pre/postconditions and for checking semantic equivalence, for a well-defined class of heap-manipulating programs. In order to understand the theoretical expressiveness of streaming transducers, we focus on streaming transducers processing strings over finite alphabets, given the existence of a robust and well-studied class of ``regular'' transductions for this case. Such regular transductions can be defined either by two-way deterministic finite-state transducers, or using a logical MSO-based characterization. Our main result is that the expressiveness of streaming string transducers coincides exactly with this class of regular transductions.

Ring signatures of sub-linear size without random oracles

Abstract: Ring signatures, introduced by Rivest, Shamir and Tauman, enable a user to sign a message anonymously on behalf of a "ring". A ring is a group of users, which includes the signer. We propose a ring signature scheme that has size O(√N) where N is the number of users in the ring. An additional feature of our scheme is that it has perfect anonymity. Our ring signature like most other schemes uses the common reference string model. We offer a variation of our scheme, where the signer is guaranteed anonymity even if the common reference string is maliciously generated.

System for parallel string search with a function-directed parallel collation of a first partition of each string followed by matching of second partitions

Abstract: A character string search arithmetic operation is performed at high speed with a small hardware scale processing module, such as a symbol string search module. The search module is connected to a CPU through address and data buses and includes a function definition section for defining a function of the apparatus in accordance with a command from the CPU, a data input/output section for receiving a symbol string to be searched through the data bus and for outputting the result of a search. A search processing section performs the search based on a function defined by the function definition section. A symbol string to be searched for, which is internally stored, is compared with the symbol string data input to the module's data input/output means. A condition holding section holds data indicative of an internal condition corresponding to the result of the search processing. Thereby, the CPU and the symbol string search module can perform the search at high speed.