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SPARQL 1.1 Query Results CSV and TSV Formats

Abstract

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.

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.

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

x,literal
http://example/x,String
http://example/x,"String-with-dquote"""
_:b0,Blank node
,Missing 'x'
,
http://example/x,
_:b1,String-with-lang
_:b1,123

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):

?x<TAB>?literal
<http://example/x><TAB>"String"
<http://example/x><TAB>"String-with-dquote\"" 
_:blank0<TAB>"Blank node"
<TAB>"Missing 'x'"
<TAB>
<http://example/x><TAB>
_:blank1<TAB>"String-with-lang"@en
_:blank1<TAB>123

A. References

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

A.1 Normative References

SPARQL11-JSON-RES

SPARQL 1.1 Query Results JSON Format, A. Seaborne, Editor, W3C Recommendation, 21 March 2013, http://www.w3.org/TR/2013/REC-sparql11-results-json-20130321. Latest version available at http://www.w3.org/TR/sparql11-results-json.

SPARQL11-QUERY

SPARQL 1.1 Query Language, S. Harris, A. Seaborne, Editors, W3C Recommendation, 21 March 2013, http://www.w3.org/TR/2013/REC-sparql11-query-20130321. Latest version available at http://www.w3.org/TR/sparql11-query.