Querying by sketch geographical databases. Yu Han 1, a *

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1 4th Internatonal Conference on Sensors, Measurement and Intellgent Materals (ICSMIM 2015) Queryng by sketch geographcal databases Yu Han 1, a * 1 Department of Basc Courses, Shenyang Insttute of Artllery, Shenyang,110162, Chna a @qq.com Keywords: Spatal Query; Topologcal Relatons; Spatal Reasonng. Abstract. Ths s where the abstract should be placed. It should consst of one paragraph gvng a concse summary of the materal n the artcle below. Replace the ttle, authors, and addresses wth your own ttle, authors, and addresses. You may have as many authors and addresses as you lke. It s preferable not to use footnotes n the abstract or the ttle; the acknowledgments of fundng bodes etc. are to be placed n a separate secton at the end of the text. Introducton Spatal data query s the bass of GIS functons. how to query a massve spatal database s currently one of the bottlenecks of spatal data management? Many spatal data query methods have been proposed such as Structural Spatal Query (SSQL), Spatal Query by Natural Language (SQNL), Vsual Spatal Query (VSQ), etc. SSQL and SQNL are query languages based on text; the descrpton of spatal relaton s obscured and easly results n the msmatch. The VSQ usage cons and nterface to organze query process, but t s very dffcult to accurately express spatal relaton of objects only use some prepared defnte cons. Therefore, the research on spatal query by sketch got value. Egenhofer[1][2] proposed the desgn prncple of the spatal data query by sketch, dscussed the representaton of the sketch and the query process. In 2000, Blaser[3] dscussed the nterface desgn of spatal query by sketch, sketch processng, system desgn of spatal query by sketch etc.in 2005, Grfon and Rafanell [4][5] studed dentfy of sketch and the query process of spatal-query-by-sketch, and analyze the ndetermnaton problem among them. In 2007, Caduff and Egenhofer[6] studed the applcaton of spatal query by sketch under the wreless network, and analyze the data delver prce of the envronment. Ths paper proposes a spatal query method by sketch usng 9-ntersecton model and Deep Drecton-Relaton Matrx. Ths method ntegrates drecton relatons and topologcal relatons and can handle all data types n geographcal databases. Spatal Query by Sketch Descrpton. Spatal-query-by-sketch uses a touch senstve nput devce-deally a touch screen wth a pen. Smulatons may be obtaned wth mce, but sketchng wth these devces s more cumbersome and therefore less effectve. A sketched query conssts of three steps, rangng from the drawng of a spatal query to ts executon aganst a database management system. Step 1: The user draws wth a pen or a mouse a prototype geometrc confguraton that matches closely the spatal stuaton he or she expects to retreve from the geographc database. Step 2: Spatal-query-by-sketch parses the sketch and dstlls the topology relaton and drectonal relaton among the objects from the sketch, and then stores the relatons as topology relaton table and drectonal relaton table for further query. Step 3: Spatal-query-by-sketch executes the query aganst the spatal database usng the SBSDQ-FC algorthm ths paper developed and retreves the scenes that match the sketch. Extracton of topologcal relatons and drectonal relatons. Spatal relatons representaton s the bass of spatal data query. Accordng to the characterstcs of spatal data and sketch queryng, ths paper manly consders the topologcal relatons and the drectonal relatons. In order to handle The authors - Publshed by Atlants Press 313

2 all data types n geographcal databases, we use 9-ntersecton model and Deep-Drecton-Relaton Matrx. The 9-ntersecton model s one of the man model of the topologcal relatons. The model s based on pont set topology, a theory that defnes the rules between two pont sets A and B, wth A or B beng ether a pont, lne, or area. A pont set of A has an nteror (A0), a boundary (A), and an exteror (A ). Topologcal relatons between two pont sets A and B are characterzed by the ntersecton of A s nteror, boundary, and exteror wth the nteror, boundary, and exteror of B. For two smple regons wthout holes, the categorzaton shows 8 dstnct topologcal relatons (Fg. 1). Fg. 1. the eght topologcal relatons between two spatal regons The Drecton-Relaton Matrx proposed by Goyal parttons the space nto nne parts whch called drecton tles. We denote those 9 drecton tles as {N,S,E,W,NE,SE,SW,NW,O}, We descrbe drecton between reference object and target object as a 3 3 matrx (Fg. 2). The value of element n the matrx ether s empty (Wth Ø symbolc representaton), or s non-empty (Wth Ø symbolc representaton). In 2000 Goyal extended the model to nclude nformaton about the ntersectons of the target object wth the boundares of drecton parttons whch called deep drecton-relaton matrx. The new model s capable of recordng drectons between arbtrary pars of pont, lne, and polygon objects. The deep drecton-relaton matrx s useful for drecton based queres n mult-resoluton spatal databases. Fg. 2. the drecton-relaton matrx The N objects n the sketch are the target objects n the query. We denote the objects as V= {V1, V2, Vn}. We can use the 9-ntersecton model and the deep drecton-relaton matrx to extract and save the topologcal relatons and drectonal relatons. We use array to save the relatons between the objects. We use the 9-ntersecton model and the deep drecton-relaton matrx to extract the relatons between the objects n Fgure 1 and establsh the topologcal relaton table and the drectonal relaton table as Table 1 and Table 2. Table 1. topologcal relatons of the sketch A B1 B2 B3 C A equal contan contan dsjont overlap B1 nsde equal dsjont dsjont dsjont B2 nsde dsjont equal dsjont meet B3 dsjont dsjont dsjont equal dsjont C overlap dsjont meet dsjont equal 314

3 Table 2. part of the drectonal relatons of the sketch A B1 B2 B3 A B B B Spatal data retreval algorthm based on sketch. The program of Spatal-Query-by-Sketch can be formally descrbed as a standard bnary constrant satsfacton problem: (1)A fnte collecton of N varables n the sketch, V1, V2, V3, Vn; (2)For each varable V,a fnte doman of V values, D={ v 1, v 2,, v }; (3)For each par of varables (V,Vj), a constrant C{, j} between D and Dj whch s smply a subset of D Dj. f ( j v l, v m ) C{, j} we say that the assgnment { V v l,vj v j m } s consstent. The goal of Spatal-Query-by-Sketch s to fnd a soluton such that for all,j,{ V v l,vj v j m } s consstent. To solve the constrant satsfacton problem, many algorthms have been proposed. Among them, one of the most effectve algorthms s the forward checkng algorthm(fc). The forward checkng algorthm constructs solutons by consderng assgnments to varables n a partcular order, whch for concreteness we take to be V1, V2, V3, Vn.suppose that we have found a consstent assgnment to the frst -1 varables, whch means that all parwse comparsons nvolvng only these -1 varables are satsfed. At ths pont, we call V1, V2, V3, V-1 the past varables, V the current varable,and the others the future varables. The characterstc data structure of the FC algorthm s a two dmensonal array Doman.The dea s that Doman j wll contan 0 f and only f the assgnment V v s consstent wth the assgnments chosen for all the past varables. j Otherwse,t contans the ndex of the frst assgned varable wth whch V v j s nconsstent. It follows that,when we are consderng a possble value v l for the current varable V,t s suffcent to look for a zero n Doman l. Any such value s guaranteed to be consst wth all past choces. When we make a successful assgnment to the current varable, we must check t aganst all outsandng values of the future varables, updatng Doman as necessary. Analyss shows that the algorthm complexty of FC s O (KN) when the number of varables s N, the largest for the doman s K, ths s far away from the requrements of the practcal applcaton.durng the process of query,the objects n the sketch are often adjacent objects n the map, accordng to ths feature we can reduce the doman sze of the varables, each tme select the objects wth the prevous relatonshp wth the neghborng felds as the next varable, whch can sgnfcantly mprove the effcency.in order to apply the method to optmze the search algorthm the followng defnton of spatal neghborhood relatons s gven based on Vorono dagram. k 315

4 Defnton 1. P s a set of spatal objects P={P1,P2,P3,...,Pn} IR2 (1 n ), P,Pj P( j,,j=1,2,3, n),if P meets Pj through at least k Vorono regons then the dstance between P and Pj s k,denoted as d(p,pj)=k,and the relatonshp between P and Pj s called k-order neghborhood relatons. Accordng to the defnton, when queryng spatal data by sketch,the current varable V nstantated wth the values v l, the next nstance of the object does not need to consder all the doman, but only need to consder those nstances whch have 1-order neghborhood relatons wth the current assgnment. Experment. A prototype of Spatal-Query-by-Sketch s under development wth methods presented n ths paper usng C#. The expermental database ncludes 1700 spatal scenes and s composed of two types of spatal scenes. the expermental results are n Table 3. We take four group of spatal scenes from the spatal database n frst experment. The precson and recall of the algorthm s up to 100% n the experment, but when the number of samples whch contan more objects, the effcency decreased slghtly. In ths experment the precson and recall has been able to reach 100% because the samples of ths experment are all taken from the spatal scene database and all objects are 1-order neghbors. Table 3. the precson and recall of the frst experment Samples Frst Second precson and counts type type recall Frst group % Second group % Thrd group % Fourth group % fourth group Conclusons Ths paper presents a sketch-based spatal data retreval method, gves the representaton of the sketch and query algorthms and ts optmzaton for practcal applcaton, the method can be used to process ntutve spatal data query n complex spatal scene. However, for large mass spatal data the processng effcency of the method s to be mproved. Future research are: (1) study of fuzzy sketch query method combned wth shape, topology and drecton based on the qualtatve representaton of the shape and spatal smlarty; (2) applcaton of ths method embedded nto the GIS. References [1] Egenhofer, Spatal-Query-by-Sketch[C], Proceedngs of the IEEE symposum on vsual languages, IEEE Computer Socety, Washngton DC, USA,1996. [2] Egenhofer M.J. Query processng n Spatal-Query-by -Sketch[J]. Journal of Vsual Languages and Computng, [3] BLASER A D. Sketchng spatal queres [D]. Mane: Unversty of Mane,2000. [4] Ferr, F., P. Grfon, and M. Rafanell. Queryng by sketch geographcal databases and ambgutes. Copenhagen, Denmark: Sprnger Verlag, Hedelberg, D-69121, Germany [5] Ferr,F.,P.Grfon and M. Rafanell. The sketch recognton and query nterpretaton by GSQL, a geographcal sketch query language. Proceedngs of the Ffth Internatonal Conference on Computer and Informaton Technology, 2005,

5 [6] Caduff,D.and Egenhofer, Geo-moble query-by-sketch. Internatonal Journal of Web Engneerng and Technology, (2):