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FHIR
Infrastructure
Work
Group
|
Maturity Level : 2 | Standards Status : Trial Use |
_filter
is
a
parameter
that
can
be
used
with
the
Search
Operation
.
It
uses
Filter
requests
have
access
to
the
same
set
of
search
parameters
that
are
available
to
the
search
operation
in
that
resource
context
on
the
server
(e.g.,
standard
parameters
defined
,
parameters
for
the
resources,
and
each
resource
,
etc.).
The
_filter
parameter
provides
a
syntax
for
expressing
a
set
of
query
expressions
on
the
underlying
resources.
Examples of filters:
Patient:
name
co
"pet"
-
all
patients
with
the
characters
"pet"
in
a
given
or
family
name
Patient:
given
eq
"peter"
and
birthdate
ge
2014-10-10
-
all
patients
with
a
given
name
of
peter,
born
on
or
after
10-Oct
2014
Observation:
code
eq
http://loinc.org|1234-5
-
all
observations
with
the
LOINC
code
"1234-5"
Observation:
subject.name
co
"pet"
-
all
observations
on
a
patient
with
the
characters
"pet"
in
a
given
or
family
name
Observation:
related[type
eq
"has-component"].target
pr
true
-
all
observations
that
have
component
observations
(note:
this
uses
one
of
the
search
parameters
defined
for
this
mechanism,
see
below)
Observation:
related[type
eq
has-component].target
re
Observation/4
-
all
observations
that
have
Observation/v
as
a
component
Observation:
subject.id
eq
3425
and
code-value-quantity
eq
code$loinc|12907-2,value$ge150|http://unitsofmeasure.org|mmol/L
-
all
observations
for
a
particular
patient
that
have
a
LOINC
code
of
"12907-2"
(Sodium
[Moles/volume]
in
Red
Blood
Cells)
AND
a
value
greater
than
"150
mmol/L"
Patient:
given
eq
"peter"
and
birthdate
ge
2014-10-10
and
_has:Observation:patient:code
eq
http://loinc.org|1234-5
-
all
patients
with
a
given
name
of
peter,
born
on
or
after
10-Oct
2014
that
have
an
observation
referring
to
them
with
a
LOINC
code
of
1234-5
The _filter syntax has the following features:
Note: The only difference between a "string" value and a "token" value is that a string can contain spaces and ')' and ']'. There is otherwise no significant difference between them.
Formal grammar for the syntax:
filter = paramExp / logExp / ("not") "(" filter ")"
logExp = filter ("and" / "or" filter)+
paramExp = paramPath SP compareOp SP compValue
paramExp = paramValue SP compareOp SP compValue
compareOp = (see table below)
compValue = string / numberOrDate / token
string = json string
token = any sequence of non-whitespace characters (by Unicode rules) except "]" and ")"
paramPath = paramName (("[" filter "]") "." paramPath)
paramValue = hasSpecifier / paramPath
hasSpecifier = "_has:" resource ":" index ":" index
resource = ALPHA (DIGIT / ALPHA)*
index = nameCharStart (nameChar)*
paramPath = paramName (("[" filter "]") "." paramValue)
paramName = nameCharStart (nameChar)*
nameCharStart = "_" / ALPHA
nameChar = "_" / "-" / DIGIT / ALPHA
numberOrDate = DIGIT (DateChar)*
dateChar = DIGIT / "T" / "-" / "." / "+"
dateChar = DIGIT / "T" / "-" / "." / "+" / ":" / "Z"
Notes about using the syntax:
This table summarizes the comparison operations available:
| Operation | Definition |
| eq | an item in the set has an equal value |
| ne | An item in the set has an unequal value |
| co | An item in the set contains this value |
| sw | An item in the set starts with this value |
| ew | An item in the set ends with this value |
| gt / lt / ge / le | A value in the set is (greater than, less than, greater or equal, less or equal) the given value |
| ap |
A
value
in
the
set
is
approximately
the
same
as
this
value.
Note that the recommended value for the approximation is 10% of the stated value (or for a date, 10% of the gap between now and the date), but systems may choose other values where appropriate |
| sa | The value starts after the specified value |
| eb | The value ends before the specified value |
| pr | The set is empty or not (value is false or true) |
| po | True if a (implied) date period in the set overlaps with the implied period in the value |
| ss | True if the value subsumes a concept in the set |
| sb | True if the value is subsumed by a concept in the set |
| in | True if one of the concepts is in the nominated value set by URI, either a relative, literal or logical vs |
| ni | True if none of the concepts are in the nominated value set by URI, either a relative, literal or logical vs |
| re | True if one of the references in set points to the given URL |
For detailed rules about the operators eq, ne, le, ge, lt, gt, sa, and eb see Search Prefixes .
The interpretation of the operation depends on the type of the search parameter it is being evaluated against. This table contains those details:
| Operation | String | Number | Date | Token | Reference | Quantity |
| eq | Character sequence is the same (case insensitive) | Number is the same incl same precision |
Date
is
the
same
including
same
precision
and
|
Token is the same, including namespace if specified (case insensitive) | n/a | Unit and value are the same |
| ne | (same) | |||||
| Co | Character sequence matches somewhere (case insensitive) | An item in the set's implicit imprecision includes the stated value | An item in the set's implicit period includes the stated value | n/a | n/a | n/a? |
| sw | Character sequence matches from first digit (left most, when L->R) (case insensitive) | n/a | n/a | n/a | n/a | n/a |
| ew | Character sequence matches up to last digit (right most, when L->R) (case insensitive) | n/a | n/a | n/a | n/a | n/a |
| gt / lt / ge / le | Based on Integer comparison of Unicode code points of starting character (trimmed) (case insensitive) | Based on numerical comparison | Based on date period comparison per 2.2.2.3 | n/a | n/a | Based on numerical comparison if units are the same (or are canonicalized) |
| pr | ||||||
| po | n/a | n/a | Based on date period comparison per 2.2.2.3 | n/a | n/a | |
| ss | n/a | n/a | n/a | Based on logical subsumption; potentially catering for mapping between tx | n/a | n/a |
| sb | n/a | n/a | n/a | Based on logical subsumption; potentially catering for mapping between tx | n/a | n/a |
| in | n/a | n/a | n/a | Based on logical subsumption; potentially catering for mapping between tx | n/a | n/a |
| re | n/a | n/a | n/a | n/a | Relative or absolute url | n/a |
Note:
eq
and
ne
are
appropriate
in
this
case
FHIR
®©
HL7.org
2011+.
FHIR
Release
4B
(v4.3.0)
hl7.fhir.r4b.core#4.3.0
R5
hl7.fhir.core#5.0.0
generated
on
Sat,
May
28,
2022
12:58+1000.
Sun,
Mar
26,
2023
15:26+1100.
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