QUERY SUPPORT FOR GMZ
Generic text-based compression models are simple and fast but there are two issues that needs to be addressed. They cannot leverage the structure that exists in data to achieve better compression and there is an unnecessary decompression step before the user can actually use the data. To address t...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-07-01
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| Series: | The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences |
| Online Access: | https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-4-W2/95/2017/isprs-archives-XLII-4-W2-95-2017.pdf |
| _version_ | 1819155738248871936 |
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| author | A. Khandelwal K. S. Rajan |
| author_facet | A. Khandelwal K. S. Rajan |
| author_sort | A. Khandelwal |
| collection | DOAJ |
| description | Generic text-based compression models are simple and fast but there are two issues that needs to be addressed. They cannot leverage
the structure that exists in data to achieve better compression and there is an unnecessary decompression step before the user can actually
use the data. To address these issues, we came up with GMZ, a lossless compression model aimed at achieving high compression
ratios. The decision to design GMZ (Khandelwal and Rajan, 2017) exclusively for GML's Simple Features Profile (SFP) seems
fair because of the high use of SFP in WFS and that it facilitates high optimisation of the compression model. This is an extension of
our work on GMZ. In a typical server-client model such as Web Feature Service, the server is the primary creator and provider of
GML, and therefore, requires compression and query capabilities. On the other hand, the client is the primary consumer of GML, and
therefore, requires decompression and visualisation capabilities. In the first part of our work, we demonstrated compression using a
python script that can be plugged in a server architecture, and decompression and visualisation in a web browser using a Firefox addon.
The focus of this work is to develop the already existing tools to provide query capability to server. Our model provides the ability
to decompress individual features in isolation, which is an essential requirement for realising query in compressed state. We con -
struct an R-Tree index for spatial data and a custom index for non-spatial data and store these in a separate index file to prevent alter -
ing the compression model. This facilitates independent use of compressed GMZ file where index can be constructed when required.
The focus of this work is the bounding-box or range query commonly used in webGIS with provision for other spatial and non-spatial
queries. The decrement in compression ratios due to the new index file is in the range of 1–3 percent which is trivial considering
the benefits of querying in compressed state. With around 75 % average compression of the original data, query support in compressed
state and decompression support in the browser, GMZ can be a good alternative to GML for WFS-like services. |
| first_indexed | 2024-12-22T15:41:45Z |
| format | Article |
| id | doaj.art-9c7cb7624db1444099c247aa9a122583 |
| institution | Directory Open Access Journal |
| issn | 1682-1750 2194-9034 |
| language | English |
| last_indexed | 2024-12-22T15:41:45Z |
| publishDate | 2017-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences |
| spelling | doaj.art-9c7cb7624db1444099c247aa9a1225832022-12-21T18:21:06ZengCopernicus PublicationsThe International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences1682-17502194-90342017-07-01XLII-4-W2959910.5194/isprs-archives-XLII-4-W2-95-2017QUERY SUPPORT FOR GMZA. Khandelwal0K. S. Rajan1Lab for Spatial Informatics, International Institute of Information Technology, Hyderabad, IndiaLab for Spatial Informatics, International Institute of Information Technology, Hyderabad, IndiaGeneric text-based compression models are simple and fast but there are two issues that needs to be addressed. They cannot leverage the structure that exists in data to achieve better compression and there is an unnecessary decompression step before the user can actually use the data. To address these issues, we came up with GMZ, a lossless compression model aimed at achieving high compression ratios. The decision to design GMZ (Khandelwal and Rajan, 2017) exclusively for GML's Simple Features Profile (SFP) seems fair because of the high use of SFP in WFS and that it facilitates high optimisation of the compression model. This is an extension of our work on GMZ. In a typical server-client model such as Web Feature Service, the server is the primary creator and provider of GML, and therefore, requires compression and query capabilities. On the other hand, the client is the primary consumer of GML, and therefore, requires decompression and visualisation capabilities. In the first part of our work, we demonstrated compression using a python script that can be plugged in a server architecture, and decompression and visualisation in a web browser using a Firefox addon. The focus of this work is to develop the already existing tools to provide query capability to server. Our model provides the ability to decompress individual features in isolation, which is an essential requirement for realising query in compressed state. We con - struct an R-Tree index for spatial data and a custom index for non-spatial data and store these in a separate index file to prevent alter - ing the compression model. This facilitates independent use of compressed GMZ file where index can be constructed when required. The focus of this work is the bounding-box or range query commonly used in webGIS with provision for other spatial and non-spatial queries. The decrement in compression ratios due to the new index file is in the range of 1–3 percent which is trivial considering the benefits of querying in compressed state. With around 75 % average compression of the original data, query support in compressed state and decompression support in the browser, GMZ can be a good alternative to GML for WFS-like services.https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-4-W2/95/2017/isprs-archives-XLII-4-W2-95-2017.pdf |
| spellingShingle | A. Khandelwal K. S. Rajan QUERY SUPPORT FOR GMZ The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences |
| title | QUERY SUPPORT FOR GMZ |
| title_full | QUERY SUPPORT FOR GMZ |
| title_fullStr | QUERY SUPPORT FOR GMZ |
| title_full_unstemmed | QUERY SUPPORT FOR GMZ |
| title_short | QUERY SUPPORT FOR GMZ |
| title_sort | query support for gmz |
| url | https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-4-W2/95/2017/isprs-archives-XLII-4-W2-95-2017.pdf |
| work_keys_str_mv | AT akhandelwal querysupportforgmz AT ksrajan querysupportforgmz |