Problems in Semantic Search

1
Problems in Semantic Search
Krishnamurthy Viswanathan and Varish
Mulwad krishna3, varish1 AT umbc DOT edu
1
2
Agenda

• Introduction
• Swoogle
• Cool things others do
• Swoogle facts/figures
• Our ideas
• References

2
3

• Why is Semantic Search significant?

3
4
Swoogle

• Swoogle is a search engine for Semantic Web (SW)
  documents
• It offers the following services
• Search SW ontologies and documents
• Search SW terms, i.e. URIs that have been defined
  as classes and properties
• Provide metadata of SW documents and support
  browsing the Semantic Web

4
5
Swoogle

• Swoogle supports two relevant query types
• Ontology Searches a small collection that
  consists only of Semantic Web Ontologies
• Document Searches all SW documents. This search
  space is much larger
• Swoogle indexes only the documents URL, the
  terms being defined in the document, explicit
  descriptions about the document, and the
  namespaces used by the document

5
6
Swoogle capabilities

• Web search
• Basic metadata e.g. url, desc, ns etc.
• Document metadata hasEncoding, hasLength etc.
• RDF metadata hasGrammar, hasCntTriple etc.
• Advanced search using Lucene features
• REST based services Compose an HTTP GET query
  and retrieve the results in the form of RDF/XML

6
7
Examples of REST queries

• A query is represented as a URL
• REST_QUERY SERVICE_URI ? PARAMS
• Example search SW documents which are classified
  as ontologies (ontoRatio gt 0)
• queryType e.g. search_swd_ontology
• searchString user constructed (see manual)
• Key
• http//logos.cs.umbc.edu8080/swoogle31/q?queryTyp
  esearch_swd_ontologysearchStringpersonkeydemo
  

7
8

• Cool things other semantic search engines do

8
9
Sindice

• Sindice is a Semantic Web search engine created
  at Digitial Enterprise Research Institute (DERI)
• Interesting things to note about Sindice
• Architecture
• Indexing

9
10
Sindice

• Sindice uses the paradigms of cloud computing for
  their architecture
• Sindice uses Hadoop / Nutch to distribute
  crawling across multiple machines
• Collected data is stored in a HBase a
  distributed column store

10
11
Sindice

• Sindice indexes based on
• Inverse Functional Properties (IFP)
• URIs
• Literals (Keywords)
• IFP An OWL cardinality restriction
• Benefits Faster Retrieval

11
12
Watson A gateway to the Semantic Web

• From the Knowledge Management Institute at the
  Open University in UK
• Interesting things to note about Watson
• Consider implicit semantic relationships
• Quality of Semantic documents
• Rich access to semantic data

12
13
Watson

• Implicit relationships between semantic web
  documents
• Equivalence (Duplicate detection)
• Quality of Semantic Documents
• Richer access to Semantic Data
• Web Interface for Humans
• SparQL end point
• Java/SOAP and REST APIs

13
14
Others

• Semantic Web Search Engine (SWSE)
• Pipelined architecture for crawling and indexing
• Improved index and storage structure
• Falcons
• Class subsumption reasoning
• Includes a Triple Store

14
15
Power Aqua

• Multi-ontology based QA system powered by
  PowerMap and Watson
• Takes inputs in the form of NL queries
• Factual queries that can be expressed as one or
  more linguistic triples
• Common wh-questions

15
16
Power Aqua

• Key challenges in order to be able to answer
  NL-questions
• Locating the ontologies relevant to a particular
  query
• Identifying semantically sound relationships
• Combining information from multiple queries

16
17
Swoogle facts/figures

• The search engine components currently run on 4
  machines
• These machines host the crawler, the Lucene
  index, the MySQL database etc. and access the NFS
• Approximately 20,000 pages are accessed by
  Swoogle everyday (which get queued)
• About 1,731,371 pure SW documents have been
  discovered

17
18
Swoogle facts/figures

• Swoogle crawler has a large queue of documents to
  be crawled and indexed
• Swoogle accesses metadata and index files over
  the NFS that makes information retrieval slower

18
19
Our Ideas Research and Engineering

• Acquire new hardware
• Parallelize Swoogle
• Focus on a particular domain
• Project Swoogle as a search engines for agents

19
20
Our Ideas Research and Engineering

• Improve Swoogles indexing scheme
• Analyze Swoogles ranking scheme
• Use of Swoogle Metadata
• Improve the usability of the website
• Google like Services

20
21
References

• Li Ding et al., "Swoogle A Search and Metadata
  Engine for the Semantic Web", Proceedings of the
  Thirteenth ACM Conference on Information and
  Knowledge Management, November 2004.
• P. Mika, G. Tummarello Web Semantics in the
  Clouds, IEEE Intelligent Systems, Volume 23 ,
  Issue 5 (September 2008)
• E. Oren, R.Delbru, M. Catasta, R. Cyganiak, H.
  Stenzhorn, G.
• Tummarello Sindice.com A document-oriented
  lookup index for open linked data. In
  International Journal of Metadata, Semantics and
  Ontologies, 3(1), 2008.
• Mathieu dAquin et al., Watson A Gateway for
  the Semantic Web ,Poster session of the European
  Semantic Web Conference, ESWC 2007
• Gong Cheng, Weiyi Ge, Honghan Wu, Yuzhong Qu ,
  Searching Semantic Web Objects Based on Class
  Hierarchies In WWW 2008 Workshop on Linked Data
  on the Web, 2008

21
22

• Questions ?

22