Introduction
This document describes the Triple-S format for survey data and
variables.
Background
The aim of the Triple-S standard is to define a means
of transferring the key elements of entire surveys between different
survey software packages across various hardware and software platforms.
This initial version of the Triple-S standard has been
devised by Keith Hughes, Stephen Jenkins and Geoff Wright. The impetus was
a paper by Peter Wills(1).
Summary
A Triple-S survey is described in two ASCII text files.
One, the Definition File, contains version and general information of the
survey together with definitions of the survey variables. This is used to
interpret the contents of the Data file. By default the Definition File
has a file extension of 'SSS' and the corresponding Data File has the same
name but with the extension 'ASC'.
The format of each of the files has been designed to
enable software read/write routines to be easy to implement. To further
aid the development process the files are relatively simple to read by
eye.
1. Data Use and Reuse, P Wills, SGCSA, Bristol England September
1992.
The Definition File
Outline
The definition file is comprised of a number of
keywords some of which have associated parameters. These describe two
aspects:
a. the file itself in terms of version number, date and time
of creation etc.
b. the survey in terms of the survey variables.
The following shows an outline of the contents of the definition file.
SSS
VERSION 1.0
DATE "date_text"
TIME "time_text"
ORIGIN "origin_text"
USER "user_text"
SURVEY
TITLE "survey_title_text"
RECORD record_id
VARIABLE variable_id
. variable_details
. END VARIABLE
.
VARIABLE variable_id
. variable_details
. END VARIABLE
END RECORD
END SURVEY
END SSS
The items shown in uppercase are keywords. Those shown
in lower case or as numeric digits are keyword parameters.
Basic Formatting Rules
1. General
a. Only characters in the ASCII range decimal 32 to
decimal 255 are considered valid - all others are ignored when read.
2. Keywords
a. The case of letters in keywords is insignificant, so a is
equivalent to A, b to B and so on.
b. Any number of space characters (decimal 32),
including none, can appear between keywords and parameters. Thus
VERSION 1.0 could be written VERSION1.0 and END SSS could appear as
ENDSSS
c. Individual keywords cannot contain embedded
space characters, thus VER SION is considered invalid.
3. Text String Parameters
a. The double quote character, decimal 34, is used to introduce and
end text strings.
b. To represent the double quote character in a string,
surround the character with braces: {"}
Alternatively use the two-digit hexadecimal ASCII equivalent
(surrounded by braces): {22}
c. To represent characters in the ASCII range
decimal 0 to decimal 31 within a string, use the two-digit
hexadecimal ASCII equivalent surrounded by braces. Any number of
consecutive characters can be surrounded by just one pair of braces,
for example to represent a CR/LF sequence within a text string
specify: {0D0A}
d. To represent a newline instruction within a string use
the special mnemonic: {NL}
e. To represent the open brace character within
a string, outside its special uses described in rules b, c and d
above, surround it with braces, thus: {{}
Alternatively, use the two-digit hexadecimal ASCII equivalent
surrounded by braces: {7B}
4. Other Parameters
a. The case of letters in other parameters is
insignificant, so that a is equivalent to A, b to B and so on.
b. Any number of space characters (decimal 32),
including none, can appear between parameters and keywords. Thus
VERSION 1.0 could be written VERSION1.0
c. Individual (non string) parameters cannot
contain embedded space characters, thus 1 .0 is considered invalid.
Formatting Recommendations
In order to improve the readability of the definition file, it is
recommended that:
1. The file is organised into lines using CR,LF
(decimal 13,decimal 10) combinations. These are ignored when read
(according to Basic Formatting Rule 1a).
2. At most one keyword, or keyword phrase, appears on one line.
3. Lines are indented with space or tab characters
to reflect the structure inherent in the file. An indent is applied
after every keyword which has a corresponding END keyword.
Definition File Keywords
This section describes the syntax and function of each of the keywords
and keyword phrases used to form a Triple-S definition file. The keywords
are shown in the order they are expected in the file.
SSS
Mandatory. Should be the first (not ignored) characters in the file.
VERSION 1.0
Mandatory. The current version is 1.0.
The following four keywords (DATE, TIME, ORIGIN and
USER) can appear in any order and are optional. Each should appear at most
once.
DATE "date_text"
Optional between VERSION 1.0 and SURVEY. The parameter
should represent the date the file was created. For example: DATE
"7th July 1994"
TIME "time_text"
Optional between VERSION 1.0 and SURVEY. The parameter
should represent the time the file was created. For example: TIME
"11:15"
ORIGIN "origin_text"
Optional between VERSION 1.0 and SURVEY. The parameter
should represent the originating system (program and operating system).
For example: ORIGIN "MyProg v2, DOS 5.00"
USER "user_text"
Optional between VERSION 1.0 and SURVEY. The parameter
should represent the user who created the file. For example: USER "A
Smith"
SURVEY
Mandatory. Introduces details of the survey.
TITLE "survey_title_text"
Optional but if present appears between SURVEY and
RECORD. The text should represent the survey title. For example: TITLE
"The Fitness Centre Survey"
RECORD record_id
Mandatory. One RECORD keyword appears after SURVEY or
after TITLE (after SURVEY). It is used to introduce the definition of the
variables. The record_id can be used in conjunction with the variable_id
(see the VARIABLE keyword) to generate a unique variable name on import.
The record_id is any single character A to Z or a to z. For example:
RECORD A
Definition File Keywords (continued)
For each variable being described there should be a block comprising:
VARIABLE variable_id
Mandatory. The variable_id is an integer number of up
to four digits, in the range 1 to 9999, with or without leading zeroes.
Each variable_id must be unique within a RECORD ... END RECORD block.
For example: VARIABLE 10
NAME "name_text"
Mandatory. The name_text should represent the name the variable had in
the original survey.
For example: NAME "Q1a"
LABEL "label_text"
Mandatory. The label_text should represent the label of the original
variable.
For example: LABEL "First visited"
TYPE type_name
Mandatory. The type of the variable as represented by type_name which
must be one of:
SINGLE
MULTIPLE
QUANTITY
CHARACTER
LOGICAL
For example: TYPE SINGLE
The details following the TYPE specification vary according to the
type_name parameter.
For SINGLE and MULTIPLE variables:
One of two methods can be used to specify the
categories for variables of type SINGLE and MULTIPLE, either the
VALUES method or the SIZE method:
VALUES Method
The VALUES method requires the definition of
label text for each value category. This is done using the VALUES
specification which consists of the VALUES keyword, followed by one
or more occurrences of a category_value number (optional) and some
category_label_text, followed by END VALUES:
VALUES
category_value "category_label_text"
category_value "category_label_text"
. END VALUES
Definition File Keywords (continued)
The first category_value is always 1. Subsequent
category_values are incremented by one, thus the final
category_value is always the same as the number of items in the
list. For example, a simple Yes/No variable might be recorded as:
TYPE SINGLE
VALUES
1 "Yes"
2 "No"
END VALUES
Or alternatively, missing out the optional category_value
numbers, by:
TYPE SINGLE
VALUES
"Yes"
"No"
END VALUES
Where omitted, category_value numbers will be
assumed from the position of the corresponding category_label_text
in the list.
SIZE Method
The SIZE method requires the definition of the
number of values but without details. It takes the form of a SIZE
specification:
SIZE size_specification
A SIZE specification is mandatory if no VALUES
specification has been given. It defines the number of category
values (that is, the number of the highest value).
For example the above Yes/No variable could alternatively be
described by:
TYPE SINGLE
SIZE 2
It is the responsibility of the importer to generate appropriate
value label text as required.
Limitations:
1. VALUES and SIZE expressions are mutually
exclusive. If a VALUES expression is used then there must be no SIZE
expression given. If a SIZE expression is used then there must be no
VALUES expression given.
2. At least one value category must be defined
(either through the VALUES specification or through the SIZE
specification).
3. There is no upper limit to the number of category values.
Definition File Keywords (continued)
For QUANTITY variables:
SIZE lowest_value TO highest_value
Mandatory. The SIZE specification explicitly
defines the valid range, and implicitly defines the format and
physical size of data for the variable. For example, if the data
represented any amount between 0 and 500 to an accuracy of two decimal
places:
SIZE 0.00 TO 500.00
Limitations:
1. The valid range can include positive or
negative values. Negative values are identified by a single leading
minus sign, '-'. Positive values are identified by the absence of a
sign.
2. The number of decimal places must be the same
for both the lowest_value and the highest_value parameters. The
number of decimal places must be identical to the number of decimal
places used to represent the data in the corresponding data file.
3. Values must contain at least one digit. The
use of a decimal point is optional for integer values. The following
table gives examples of correct and incorrect representations:
4. There is no upper or lower limit to the values
that may be assigned to a quantity variable.
Definition File Keywords (continued)
For CHARACTER variables:
SIZE size_specification
Mandatory. Defines the maximum length of data for
the variable.
For example: SIZE 20
Limitations:
1. The size_specification must be at least 1.
2. There is no upper limit to the size_specification.
For LOGICAL variables:
No keywords or parameters are used to amplify the specification
of LOGICAL type variables.
Finally, for all variable types:
END VARIABLE
Mandatory. Completes definition of the variable.
Then either the definition of another variable (introduced by VARIABLE
variable_id), or:
END RECORD
Mandatory. Finishes the definition for the set of variables.
END SURVEY
Mandatory. Finishes the definition for the survey.
END SSS
Mandatory. Finishes the file. Anything after this will be ignored.
The Data File
Overview
The data file is comprised of fixed-length records.
Each record registers the responses for each of the variables in the
corresponding definition file given by one respondent.
Data is recorded in fields of fixed length and arranged
in the order defined by the variables in the definition file. The length
of each field is determined from the type and size of the corresponding
variable.
Basic Formatting Rules
1. Other than the record terminator (see below),
only characters in the range decimal 32 to decimal 255 are considered
valid - any others are considered an error when read.
2. The length of each record is determined by the
corresponding definition file. The length is actually the sum of the
lengths determined by the variables in the definition file (see
below). There is no maximum record length.
3. Each record is terminated by either CR/LF,
LF/CR, CR or LF, where CR is the carriage return character (decimal
13) and LF is the line feed character (decimal 10). Whichever
terminator is used must be employed consistently - that is the same
terminator must be used throughout the file.
4. The number of respondents is determined by the
number of records in the file. There is no maximum number of records
(and hence respondents) in the file.
5. There is no specific end-of-file character. The end of the file
is determined by its physical size.
Individual Data Items
The following describe the methods used to represent
data for each type of variable. In all cases, a field comprised of space
characters represents missing data.
Variables of type SINGLE
Data is recorded as an integer number ranging from 1 to
the number of values specified for the corresponding variable. The number
0 can be used to represent missing data.
The length is the minimum number of characters required
to represent the largest value. Thus, variables with up to 9 values have a
data field one character long; variables with from 10 to 99 values have a
data field length of 2, and so on. If a particular number is smaller than
the maximum for the field, it should be right justified using leading
space or zero characters as padding.
For example, the seventh category value of a variable with 20 values
would appear as: 07
Variables of type MULTIPLE
Data is recorded with one character per value of the
corresponding variable. A character 1 is used to signify that a value has
been selected, a character 0 signifies that a value is not selected.
The length is the number of values of the corresponding variable.
For example, a multiple variable with 5 values where
the second and fifth values are selected would be recorded as: 01001
Variables of type QUANTITY
Data is recorded as a number with the same number of decimal places as
were used in the SIZE specification of the corresponding (QUANTITY type)
variable. A decimal point should always appear if one was used in the
corresponding SIZE specification.
Data is as long as required to accomodate the longest allowable
value defined by the SIZE specification of the corresponding variable.
When calculating the physical size of data for the variable, an allowance
should be made for the sign of negative values. Negative numbers are
represented with a leading minus sign, '-'. No such allowance should be
made for (the sign of) positive values. If a particular value can be
represented in a smaller length then leading spaces are used as padding.
For example, a data value of 1 for a quantity variable of: SIZE 0.5 TO
1.5 would be recorded as: 1.0
Individual Data Items (continued)
Variables of type CHARACTER
Data is recorded as the original character string.
The length of the field is simply the value defined by
the SIZE parameter of the corresponding variable. Data shorter than the
maximum length is left justified and padded to the maximum length with
trailing spaces.
For example a character variable of: SIZE 10 and data
as the word 'CHARACTER' would be recorded as: CHARACTER
Variables of type LOGICAL
Data is recorded such that character 0 represents FALSE and character 1
represents TRUE.
The length of the field is always one character.
For example, a value of true would be represented as: 1
Examples
Example Triple-S Definition File
The example defines a survey with five variables (one
each of types SINGLE, MULTIPLE, CHARACTER, QUANTITY and LOGICAL).
SSS
VERSION 1.0
DATE "06/06/94"
TIME "16:55"
ORIGIN "MyProg v2, DOS 5.00"
USER "Ann Analyst"
SURVEY
TITLE "Historic House Exit Survey"
RECORD V
VARIABLE 1
NAME "Q1"
LABEL "Number of visits"
TYPE SINGLE
VALUES
1 "First visit"
2 "Visited before within the year"
3 "Visited before that"
END VALUES
END VARIABLE
VARIABLE 2
NAME "Q2"
LABEL "Attractions visited"
TYPE MULTIPLE
VALUES
1 "Sherwood Forest"
2 "Nottingham Castle"
3 "{"}Friar Tuck{"} Restaurant"
4 "Other"
END VALUES
END VARIABLE
VARIABLE 3
NAME "Q3"
LABEL "Other attractions"
TYPE CHARACTER
SIZE 30
END VARIABLE
Example Triple-S Definition File (continued)
VARIABLE 4
NAME "Q4"
LABEL "Miles travelled"
TYPE QUANTITY
SIZE 1 TO 999
END VARIABLE
VARIABLE 5
NAME "Q5"
LABEL "Enjoyed visit"
TYPE LOGICAL
END VARIABLE
END RECORD
END SURVEY
END SSS
Example Triple-S Data File
21011Amusement Park 0121
30100 0031
21001"Marco's" Restaurant 0580
The above data corresponds to respondent data as follows:
Respondent 1:
Number of visits: Visited before within the year [2]
Attractions visited: Sherwood Forest [1]
"Friar Tuck" Restaurant [3]
Other [4]
Other attractions: Amusement Park
Miles travelled: 12
Enjoyed visit: TRUE
Respondent 2:
Number of visits: Visited before that [3]
Attractions visited: Nottingham Castle [2]
Other attractions:
Miles travelled: 3
Enjoyed visit: TRUE
Respondent 3:
Number of visits: Visited before within the year [2]
Attractions visited: Sherwood Forest [1]
Other [4]
Other attractions: "Marco's" Restaurant
Miles travelled: 58
Enjoyed visit: FALSE
