Information extraction for building knowledge basis

Editor's Notes

• #27: The spatial layout of content elements of a Web page helps human readers to understand the semantics of contents. In this page a user is able to identify details of a music band because descriptive information are close to the image and each music band is shown by using the same visual pattern._____________________________________________________________________ Introduction of human oriented,Browser makesrectangles *** usa la pagina last-fm***The web designer represent the pages for representing unitaria information L’Unitarietà is given by the spatial consistency of an information that give the semantics to a user and we want exploit such spatial consistency for query the pages. This is possible by exploiting as funzionano the layout engineThis is a page presentation oriented *** mettere last-fm col browser**Its internal representation in thisThe layout that make the browser is this.*** illuminare**The spatial layout of nodes ** mettere un rettangolo*** allow user to identify some homogeneous part of information that are the descriptions of these music band.This means presentation oriented human orientedi.e. the human understand that this information are referred to the same music band because they have a certain spatial continuity
• #28: Layout engines of Web browsers assign a rectangle to each DOM element. ___________________________________________________The internal code of a page is this How can we query the page using the spatial information?The browser when visualize the pages represent the information in their rectangles that we can call minimum bounding rectangle. In fact the layout engine assign to each node*** parallelotraildom e quellochevedi--- vedicoldplayèscritto qua dentro e siillumina, img e siillumina***For each node based on the stylesheet, what the web designer.Presentation oriented, all also the style is used for give emphasis so that the human understand the important information, so the name in bold. (sviluppifuturiusarli)
• #29: As shown in the the figure the complex, involved and nested structure of the DOM has a clear presentation that enable user to read and understand the meaning of information presented in the Web page.
• #32: The rectangular algebra is an extension of the Allen’s interval algebra to the two dimensional case. For example in this case the relatio x (b,e) y is intuitively obtained by applying interval algebra to both sides of the rectangle.__________________________________________________________So we could use the spatial model of geospatial database for representing the mutual relationships between objects***Mostra RA***The rectngular algebra define 169 relations, all the possible relations between rectangles *** mostrare la figurona***Between this and this in the relation algebra this relation is called so*** illumina****** Ritaglia un singolo rettangolo***-----------------Modelli del mondo geospaziale per rappresentare le mutue relazioniRAIlluminare 2 - albero non basato del nesting ma su contenimento e relazioni
• #33: In order to allow the representation of spatial relations existing between pairs of content items/rectangles laid out by the layout engine of a Web broser in the presentation of a Web page, we use the rectangular algebra relations model. This model is well known and widely adopted in geo-Spatial databases and has very interesting properties like invertibility that enable optimized evaluations of SXPath language.____________________________________________So we could use the spatial model of geospatial database for representing the mutual relationships between objects***Mostra RA***The rectngular algebra define 169 relations, all the possible relations between rectangles *** mostrare la figurona***Between this and this in the relation algebra this relation is called so*** illumina****** Ritaglia un singolo rettangolo***-----------------Modelli del mondo geospaziale per rappresentare le mutue relazioniRAIlluminare 2 - albero non basato del nesting ma su contenimento e relazioni
• #34: No comment. Già tutto nella slide.and has very interesting properties like invertibility that enable optimized evaluations of SXPath language._______________________________________So we could use the spatial model of geospatial database for representing the mutual relationships between objects***Mostra RA***The rectngular algebra define 169 relations, all the possible relations between rectangles *** mostrare la figurona***Between this and this in the relation algebra this relation is called so*** illumina****** Ritaglia un singolo rettangolo***-----------------Modelli del mondo geospaziale per rappresentare le mutue relazioniRAIlluminare 2 - albero non basato del nesting ma su contenimento e relazioni
• #35: By representing RA relations/spatial relation we obtain the SDOM where continuous arrows represent spatial containment and dotted arrows represent RA relations. This way we have a model of a Web page that represent all spatial relations existing between each pair of DOM nodes.Spatial relations enable also the definition of a spatial ordering along the 4 main direction North, South, East, and West as shown in the figure._____________________________Intuizione di DOMSo I can make a tree of the page not based on nesting of tags, but by using the spatial containment and spatial relations*** tirare fuori l’sdom****** sempre animando, mostrando sempre I due elementi scelti, ***Between image and radiohead there is the spatial relation (s, bi)I can represent this data model that do not capture the simple nesting of tags but catcht the spatial arrangment of the objects on the page*** con le animazioni***This is the new data model that I use called Spatial DOM. That is the Document Object Model with the objects of the DOM where the relations (queste scure) are containment relations, (quelle tratteggiate) are the Rarelations.It allows to introduce an ordering in the page using this model ----------------Nuovo modello che uso SDOMIntrodurre che permette di definire ordinamento spaziale nella pagina
• #36: The RA relation is too fine grained and verbose, difficult to use by a human. So we introduce also the Rectangular Cardinal Relations and topological relations (Two of the most intuitive and diffused spatial models) in order to map RA relations and allow user to query spatial relations in a more intuitive way.________________________________________________________Such relations are very complicated We need more intuitive relations to use So we use another geospatial model called RCR and Topological relations mapped with the RA modelDivide in regional tiles and it is simple
• #37: The RA relation is too fine grained and verbose, difficult to use by a human. So we introduce also the Rectangular Cardinal Relations and topological relations (Two of the most intuitive and diffused spatial models) in order to map RA relations and allow user to query spatial relations in a more intuitive way.________________________________________________________Such relations are very complicated We need more intuitive relations to use So we use another geospatial model called RCR and Topological relations mapped with the RA modelDivide in regional tiles and it is simple
• #38: In this slide is show a comparison between Xpath and SXPath. Suppose a user that need to extract details of a music band. By using Xptah the user need to know the intricate DOM structure. By using SXPth the user can exploit the visual pattern adopted by the Web designers for organizing details of the music bands._______________________
• #39: In this slide is show a comparison between Xpath and SXPath. Suppose a user that need to extract details of a music band. By using Xptah the user need to know the intricate DOM structure. By using SXPth the user can exploit the visual pattern adopted by the Web designers for organizing details of the music bands._______________________
• #40: SXPath expressions are also resilient. In fact, a gicen visual pattern can be queried in the same way on different web pages having different internal encodings.____________________________________Another advantage is that it is more general For instance, with only a query I can catch different DOMs because their spatial representation is the same.So it generalize the patterns Our language catch visual patterns, catch in general way visual patterns on Web pages Example 2A single data record can be split in different sub-treesWrapper induction techniques like DEPTA [Zhai et al.] recognize datarecords when they are encoded in the DOM as consecutive similarsubtrees-------------------Esempio 2Altrovantaggioacchiappo DOM diversiIl linguaggiocattura in manieragenerale pattern visuali
• #42: The SXPath language has been thought for supporting information extraction from presentation-oriented documents. It derives from Xpath so it do not requires the user to learn it from scratch.It is simple to learn and more human oriented than Xpath.SXPath maintain polynomial combined complexity and constitutes a stepping stone for different kinds of Web applications aimed at acquiring infromaiton from the Web.___________________
• #44: The SDOM essentially is the traditional DOM enriched by the set of rectangular algebra relations between each pair of nodes.________________________________________
• #45: The SXPath language is an extension of the XPath language. So beside traditional axes the SXPath language provides users with a new set of axes called spatial axed. Spatial axes are expressed by rectangular cardinal relations and topological relations that are more intuitive to use for human and that can be easily mapped into rectangular algebra relations.____________________________________
• #46: Spatial axes are defined as interpreted binary relations expressed by RCR and mapped into RA by the means of the function mu.________________________________________
• #47: As said before the SXPath language extends the Xpath language by spatial axes and spatial position functions.We have studied interesting fragments of SXPath corresponding to XPath fragments already studied in literature in order to have a clear picture of expressivity and complexity of the language. In particular, we studied the Core Xpath/SXPath (navigational core of Xpath/SXPath) and the WF/Spatial WF fragments (that allow position/spatial position functions).____________________________
• #48: The semantics of SXPath is given by using the concept of context introduced by Wadler and aopted also by Gottlob in its studies on XPath expressivity and complexity.In SXPath the context must be extended to spatial positions of nodes and context sizes for each direction. So we have a 12-tuple instead of a 3-tuple_____________________________________________________________________________
• #49: We have given the formal semantics of SXPath by using the denotation semantics approach. So in the main difference over the XPath formal semantics is given by the function that computes the spatial axes defined as shown here.____________________________________________________
• #50: Obviously, each expression is evaluated over the context as shown here.Of couse________________________________
• #51: The study of combined computational complexity of different SXPath fragments shows that SXPath maintain Polinomial time computational complexity. Obviously SXPath as a greater exponent in the polynomial because of the quadratic number of relation stored in the SDOM that need to be explored during the evaluation of spatial axes.We compute spatial axes by using the same dynamic programming approach suggested by Gottolob but we have to explore a quadratic number of further relation in the SDOM.________________________________________ Core SXPath queries can be evaluated in time O(SDS2 á SQS) where SDSis the size of the XML document, and SQS is the size of the query QProof Sketch There are O(SVv S2) many spatial relations to beconsidered in addition to the O(SVS) many relations of the DOMincurring a higher polynomial worst case complexityIn order to obtain a polynomial-time combined complexity bound for SXPathquery evaluation we use dynamic programming adopting the Context-ValueTable (CV-Table) principle introduced by Gottlob et al.Position and size are computed on demand, we compute all spatial positionfunctions in a loop for all pairs previousÉcurrent nodesFull SXPath computational costs are dominated by String Operations belongingto XPath 1.0In SWF the computation of spatial ordering generates a higher polynomial worstcase than XPath 1.0
• #53: The architecture of the system consists in a parser of SXPath expressions (Query parser), a builder of the SDOM an engine that efficiently evaluates SXPath queries.______________________
• #54: The GUI shows the DOM, allows to write queries, enables to check query results that are show on the screen._________________________________________
• #55: In these two log-log plots are shown data efficiency and query efficiency. For evaluating data efficiency we used a growing document size, while for evaluating query efficiency we used a query with increasing number of location steps.Plots show that the system behavior is polynomial with respect to both data and query sizes._________________________________________________________
• #56: For evaluating the usability we asked some students that already know the Xpath language to learn SXPath and use it for extracting product names and prices from a web pages.The experiment has shown that user found the language usable and effective._________________________________________________
• #57: In the second experiment we evaluated the effectiveness of Sxpath with respect to Xpath. We discovered that the possibility to exploit the visual appearance of Web pages allow to write queries by less attempts than in Xpath, that Sxpath location path are more syntetic and that Sxpath is resilient (the same query can be used on different Web site having very different internal encodings in terms of DOM trees).________________________________
• #58: In the second experiment we evaluated the effectiveness of Sxpath with respect to Xpath. We discovered that the possibility to exploit the visual appearance of Web pages allow to write queries by less attempts than in Xpath, that Sxpath location path are more syntetic and that Sxpath is resilient (the same query can be used on different Web site having very different internal encodings in terms of DOM trees).________________________________
• #59: In the second experiment we evaluated the effectiveness of Sxpath with respect to Xpath. We discovered that the possibility to exploit the visual appearance of Web pages allow to write queries by less attempts than in Xpath, that Sxpath location path are more syntetic and that Sxpath is resilient (the same query can be used on different Web site having very different internal encodings in terms of DOM trees).________________________________
• #60: In presentation-oriented documents the layout of elements in the internal representation provides visual cues that help human user to understand the meaning of contents.Both contents of Web pages and PDF documents are presented to users on a two dimensional Cartesian plane. The meaning of contents is clear only after rendering. For example, the PDF encoding consists in a (completely flat) stream of strings equipped with position in which they must appear on the page. The table in the figure can be understood only after rendering_________
• #61: By using document layout analysis and document understanding techniques, combined with table recognition methods, different parts of a PDF document can be recognized. This way element of a PDF document can be represented in a more abstract format like DOM or SDOM._________________