SPARQL 1.1 Query Results CSV and TSV Formats

W3C Working Draft 01 May 2012

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Andy Seaborne, The Apache Software Foundation


The formats CSV [RFC4180] (comma separated values) and TSV [IANA-TSV] (tab separated values) provide simple, easy to process formats for the transmission of tabular data. They are supported as input datat formats to many tools, particularly spreadsheets. This document describes their use for expressing SPARQL query results from SELECT queries.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document describes two simple additional results formats that have been found to be convenient in practice when consuming data obtained with SPARQL. They complement the other standard formats in XML and in JSON.

The set of SPARQL 1.1 Recommendations comprises:

This document was produced by the SPARQL Working Group, which is part of the W3C Semantic Web Activity.

This document was published by the SPARQL Working Group as a Last Call Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to public-rdf-dawg-comments@w3.org (subscribe, archives). The Last Call period ends 01 June 2012. All feedback is welcome.

The SPARQL WG welcomes reports of implementations, sent to the comments address. If we gather sufficient evidence of interoperable implementations, the group may request to skip Call for Implementations (Candidate Recommendation) drafts and have the next round of publications be Proposed Recommendations.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This is a Last Call Working Draft and thus the Working Group has determined that this document has satisfied the relevant technical requirements and is sufficiently stable to advance through the Technical Recommendation process.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of Contents

1. Introduction

This document describes CSV and TSV formats for expressing the results of a SPARQL SELECT query. They provide lowest common denominator formats between systems using different implementation technologies.

Other formats for expression SPARQL results are the SPARQL XML Results Format [RDF-SPARQL-XMLRES] and SPARQL JSON Results Format [SPARQL11-JSON-RES]. Each format is useful in different application scenarios.

The SPARQL Results CSV Results Format is a lossy encoding of a table of results. It does not encode all the details of each RDF term in the results but instead just gives a string without indicating the type of the term (IRI, Literal, Literal with datatype, Literal with language, or blank node). This makes it simple to consume data, such as text and numbers, in applications without needing to understand the details of RDF. In some applications, guesses as to which elements are hyperlinks are made pragmatically, for example, guessing that strings starting "http://" are links.

The SPARQL Results TSV Results Format does encode the details of RDF terms in the results table by using the syntax that SPARQL [SPARQL11-QUERY] and Turtle [TURTLE] use. An application receiving a TSV-encoded results set can split each line into elements of the result row, and extract all the details it wishes to process of the RDF terms by simple string processing, without a complete XML or JSON parser required by the more complex SPARQL result formats.

When this document uses the words must, must not, should, should not, may and recommended, they must be interpreted as described in RFC 2119 [RFC2119].

1.1 Example

The following artificial example is used to illustrate the features of serializing results in each format.

x literal Comment (not part of the table)
<http://example/x> String An IRI and a string consisting of characters S-t-r-i-n-g
<http://example/x> String-with-dquote" String with a double quote in it.
_:b0 Blank node Blank node
Missing 'x' No RDF term for the x column
This row has no terms in it.
<http://example/x> No term in the literal column.
_:b1 "String-with-lang"@en An RDF literal with a language tag
_:b1 123 An RDF literal, datatype xsd:integer, and lexical form 123.

2. Transmission issues using CSV and TSV Formats

The SPARQL results formats described here confirm to the formal specifications of the relevant formats, Comma Separated values (CSV) [RFC4180] and Tab Separated Value (TSV) [IANA-TSV].

Systems providing these formats should note that the content types for CSV is text/csv and for TSV text/tab-separated-values. Being text/*, the default character set is US-ASCII. The charset parameter should be used in conjunction with SPARQL Results; UTF-8 is recommended: text/csv; charset=utf-8 and text/tab-separated-values; charset=utf-8.

The end-of-line in CSV is CRLF i.e. Unicode codepoints 13 (0x0D) and 10 (0x0A).

The end-of-line in TSV is EOL i.e. Unicode codepoint 10 (0x0A).

Applications reading these formats are advised to cope with both CRLF and LF as end of line markers and not rely on conformance to the formal specifications.

3. CSV - Comma Separated values

In the SPARQL Results CSV Format, the results table is serialized as one line listing the variables in the results, using the CSV header line, followed by one line for each query solution (a line may end up split by newlines in the data). Values in the results are strings, for URIs, literals and blank nodes, together with numbers when the literals are of numeric XSD datatype.

3.1 Serializing the Results Table

The first line of a SPARQL CSV Results Format response is the header line giving the names of the variables used in the result set. The header line consists of the variable names, without leading ?, separated by commas.

While the text/csv format does not require a header row, the SPARQL CSV Results Format must use a header row. If the content type parameter header is used, it must be header=present.

The remaining rows are the values of the results, with each binding determined by the position in the row, corresponding to the entry in the header line.

If a variable is not bound, an empty field is used (e.g. ,,). Each row must have the same number of fields, with each field corresponding to a binding to the variable in the header line in the same field position.

3.2 Serializing RDF Terms

The entry in each field is the string corresponding to the RDF term value. (c.f. SPARQL STR()) without syntax to denote what kind of term it is. The encoding quoting rules of CSV format must be used.

Blank nodes use the _:label form from Turtle and SPARQL. Use of the same label indicates the same blank node within the results but has no significance outside the results.

Fields containing any of " (QUOTATION MARK, code point 34, 0x22 in Unicode[UNICODE]), , (COMMA, code point 44, 0x2C), LF (code point 10, 0x0A) or CR (code point 13, 0x0D) must be quoted using the quoting mechanism of RFC4180 [RFC4180]. Fields are limited by a pair of quotation marks " (code point 0x22). Within quote strings, all characters except ", including new line characters have their exact meaning - newlines do not end a CSV record. " is written using a pair of quotation marks "".

The standard CSV format does not distinguish between missing values and empty strings. The SPARQL 1.1 CSV Results Format uses the same representation for unbound variables as for variables bound to an empty string literal. The other SPARQL Result formats (based on JSON, TSV or XML) can be used if this distinction is required.

3.3 Example of CSV-Serialized Results

_:b0,Blank node
,Missing 'x'

4. TSV - Tab Separated values

In the SPARQL Results TSV Format, the results table is serialized as one line listing the variables in the results, followed by one line for each query solution. All RDF terms used in the format are encoded in the format specified by Turtle [TURTLE] except that the triple quoted forms for the lexical part of literals must not be used. These forms would allow raw newlines and tabs that form part of the TSV format. A TSV format SPARQL result set must use the single quoted literal forms, together with any necessary escapes such as \t, \n and \r.

4.1 Serializing the Results Table

The results table is serialized as one line listing the variables in the results, followed by one line for each query solution. This first line is required by the TSV format [IANA-TSV], unlike CSV, where it is optional.

Variables are serialized in SPARQL syntax, using question mark ? character followed by the variable name.

Each row of the result set is serialized by sequence of RDF terms in SPARQL syntax, separated by a tab (Horizontal Tab, Unicode codepoint 9) character.

If a variable is not bound in a row, an empty field is used. Each row must have the same number of fields, corresponding to the variables listed in the first row.

4.2 Serializing RDF Terms

The SPARQL Results TSV Results Format serializes RDF terms in the results table by using the syntax that SPARQL [SPARQL11-QUERY] and Turtle [TURTLE] use.

IRIs enclosed in <...>, literals are enclosed with double quotes "..." or single quotes ' ...' with optional @lang or ^^ for datatype. The quotes around the lexical form is required. Tab, newline and carriage return characters (Unicode codepoints 0x09, 0x0A (line feed) and 0x0D (Carriage Return)) are encoded in strings as \t, \n and \r respectively. The long string forms using triple quotes """ and ''' must not be used.

The abbreviated forms for numbers (XSD integers, decimals and doubles) should be used.

Blank nodes use the _:label form from Turtle and SPARQL. Use of the same label indicates the same blank node within the results but has no significance outside the results.

4.3 Example of TSV-Serialized Results

Writing <TAB> for a raw tab character (Unicode code point 9):

_:blank0<TAB>"Blank node"
<TAB>"Missing 'x'"

A. References

This section includes references not yet included in the standard biblio DB

A.1 Normative References

Andy Seaborne. SPARQL 1.1 Query Results JSON Format W3C (in-progress) Working Draft. URL: http://www.w3.org/TR/sparql11-results-json
Steve Harris, Andy Seaborne. SPARQL 1.1 Query Language W3C (in-progress) Working Draft. URL: http://www.w3.org/TR/sparql11-query

A.2 Non-normative References

B. References

B.1 Normative references

Paul Lindner. Definition of tab-separated-values (tsv) June 1993. IANA Media Type Registration. URL: http://www.iana.org/assignments/media-types/text/tab-separated-values
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Internet RFC 2119. URL: http://www.ietf.org/rfc/rfc2119.txt
Y. Shafranovich. Common Format and MIME Type for Comma-Separated Values (CSV) Files October 2005. Internet RFC 3987. URL: http://www.ietf.org/rfc/rfc4180.txt
David Beckett, Tim Berners-Lee. Turtle: Terse RDF Triple Language. January 2008. W3C Team Submission. URL: http://www.w3.org/TeamSubmission/turtle/

B.2 Informative references

Jeen Broekstra; Dave Beckett. SPARQL Query Results XML Format. 15 January 2008. W3C Recommendation. URL: http://www.w3.org/TR/2008/REC-rdf-sparql-XMLres-20080115
The Unicode Consortium. The Unicode Standard. 2003. Defined by: The Unicode Standard, Version 4.0 (Boston, MA, Addison-Wesley, ISBN 0-321-18578-1), as updated from time to time by the publication of new versions URL: http://www.unicode.org/unicode/standard/versions/enumeratedversions.html