INFORMATION EXTRACTION FROM TEMPLATE-GENERATED HIDDEN WEB DOCUMENTS

The larger amount of information on the Web is stored in document databases and is not indexed by general-purpose search engines (such as Google and Yahoo). Databases dynamically generate a list of documents in response to a user query – which are referred to as Hidden Web databases. Such documents are typically presented to users as templategenerated Web pages. This paper presents a new approach that identifies Web page templates in order to extract queryrelated information from documents. We propose two forms of representation to analyse the content of a document – Text with Immediate Adjacent Tag Segments (TIATS) and Text with Neighbouring Adjacent Tag Segments (TNATS). Our techniques exploit tag structures that surround the textual contents of documents in order to detect Web page templates thereby extracting query-related information. Experimental results demonstrate that TNATS detects Web page templates most effectively and extracts information with high recall and precision

Sampling, Information Extraction and Summarisation of Hidden Web Databases

Hidden Web databases maintain a collection of specialised documents, which are dynamically generated in response to users’ queries. The majority of these documents are generated through Web page templates, which contain information that is often irrelevant to queries. In this paper, we present a system designed to detect and extract query-related information from documents sampled from databases. The proposed system, 2PS, is based on a two-phase framework for the sampling, extraction and summarisation of Hidden Web documents. In the first phase, 2PS queries databases with random terms selected from those contained in their search interface pages and the subsequently retrieved documents – this phase retrieves a pre-determined number of sampled documents. In the second phase, it detects Web page templates from the sampled documents in order to extract information relevant to respective queries from which a content summary is generated. 2PS is validated through the implmementation of a prototype system. Its evaluation is performed through experiments on a number of real-world Hidden Web databases. The experimental results demonstrate that 2PS effectively eliminates irrelevant information contained in Web page templates and generates terms and frequencies with improved accuracy

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified