SNOMED Documentation Search


 Other Documents

Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

The form in which records are represented may have a substantial impact on the efficiency, accuracy and completeness of retrieval. The forms that best suit retrieval may differ from the forms that are required to meet the principles of clinically safe and legally valid

Gloss
telectronic health records
.

Anchor
_231f8203-345d-4188-95d3-66c07ebf7176
_231f8203-345d-4188-95d3-66c07ebf7176
Storing information as entered

This option leaves information in the form entered in the

Gloss
telectronic health record
with no additions to assist future retrieval. The application must do all the work needed to locate the required records and compute subsumption and
Gloss
tequivalence
when a request is made to retrieve data.

...

An innovative approach to the issues raised by literal storage of

Gloss
tpostcoordinated expressions
is to implement an
Gloss
texpression
repository. Each unique
Gloss
texpression
used in the system is stored in a referenced database table and assigned an internal unique
Gloss
tIdentifier
(e.g. a
Specref
RefTypedata type
tUUID
). When an
Gloss
texpression
is used in a clinical record entry the unique
Gloss
texpression
id is used to reference the
Gloss
texpression
in the repository.

The key advantages of this approach of this approach are:

Anchor
_ef18d02c-57a9-4cdc-92ee-c0730eb8997e__b
_ef18d02c-57a9-4cdc-92ee-c0730eb8997e__b

  • The
    Gloss
    Spacetrue
    texpression
    Gloss
    tIdentifier
    can have a fixed size whereas a
    Gloss
    tpostcoordinated expression
    in of variable and indeterminate size. This significantly improves storage and index efficiency.
  • The
    Gloss
    texpression
    repository can also be used to store
    Gloss
    tnormal form
    representations of each
    Gloss
    texpression
    and to relate these to the original
    Gloss
    texpression
    . This optimizes performance for
    Gloss
    texpression
    normalization during retrieval.
  • The
    Gloss
    texpression
    repository could also be processed by a
    Gloss
    tDescription Logic Classifier
    and a
    Gloss
    ttransitive closure
    table of all the
    Gloss
    texpression
    used in the application could then be generated.
    Gloss
    tpostcoordinated
    retrieval would then be highly optimized by using the
    Gloss
    ttransitive closure
    to test a single join between each predicate and the candidate
    Gloss
    texpressions
    .

Related Links

...

One possible approach to optimization of retrieval is to

Gloss
ttransform
the original stored information into an equivalent representation with the minimum number of
Gloss
tpostcoordinated
components.

The objective of this approach is to allow the generation of simple indices for the

Gloss
tprecoordinated
representation. It is then possible to undertake most retrievals using the scg-expression
Concept
ShowParts
t
term
116680003|is
a|
ShowFormatinline
Gloss
tsubtype hierarchy
to compute whether
Gloss
tConcepts
in the record are
Gloss
tsubtypes
of the
Gloss
tConcepts
used to specify retrieval. Where
Gloss
tpostcoordination
is required, the minimum number of additional tests are required to confirm that a
Gloss
tConcept
in the record meets the specified retrieval criteria.

One difficulty with this approach is that there may be more than one representation that requires the same degree of

Gloss
tpostcoordination
. This is discussed in more detail and illustrated in Transforming expressions to normal forms .

If this approach is adopted additional rules need to be applied to determine the choice between alternatives with a similar number of

Gloss
tpostcoordinated
components.

Example:

In the hypothetical example illustrated in , the

Gloss
tConcept
"red steel pedal bicycle", for which no
Gloss
tprecoordinated
representation exists, could be represented as:

"red pedal bicycle" +

scg-expression
Concept
ShowParts
t
term
|make
of|
= scg-expression
Concept
ShowParts
t
term
|steel|

or

"steel pedal bicycle" + " color " = "red"

Both are equally close to the objective of minimizing

Gloss
tpostcoordination
. A rule is needed to determine which of these is preferred. There is no obvious right or wrong solution to this but a simple rule that places the attributes in an
Specref
RefTypefield
torder
will, if applied consistently, allow all
Gloss
tpostcoordinated
representations to be reduced to a single minimized form.

...

An alternative approach is to expand any

Gloss
Spacetrue
tprecoordinated
Gloss
tconcepts
in the record to their fullest possible
Gloss
tpostcoordinated
forms. This general type of
Gloss
ttransformation
is illustrated in Transforming expressions to normal forms .

This approach requires a richer record structure but has the advantage that there are three possible end-points to

Gloss
tpostcoordination
, each of which ensures that any computably equivalent representations of
Gloss
tConcepts
will expand to an identical
Gloss
tpostcoordinated
form. The three end-points are summarized here:

  • Short
    Gloss
    tcanonical form
    :
    • This is the most parsimonious of the three options.
    • A
      Gloss
      tconcept
      is represented as the combination of:
      • Gloss
        Spacetrue
        tSubtype
        Gloss
        trelationships
        with its most proximate
        Gloss
        tprimitive
        supertypes;
      • The recorded
        Gloss
        tqualifier
        values and/or
        Gloss
        tdefining characteristics
        that distinguish it from its most proximate
        Gloss
        tprimitive
        supertypes.
  • Long
    Gloss
    tcanonical form
    :
    • This option is more verbose as it includes some redundancy.
    • A
      Gloss
      tconcept
      is represented as the combination of:
      • Gloss
        Spacetrue
        tSubtype
        Gloss
        trelationships
        with its most proximate
        Gloss
        tprimitive
        supertypes;
      • All of its recorded
        Gloss
        tqualifier
        values and/or
        Gloss
        tdefining characteristics
        , irrespective of whether they are shared by its most proximate
        Gloss
        tprimitive
        supertypes.
  • Exhaustive
    Gloss
    tpostcoordinated
    form:
    • This option is extremely verbose.
    • A
      Gloss
      tConcept
      is represented as a combination of:
      • Gloss
        Spacetrue
        tSubtype
        Gloss
        trelationships
        with all of its
        Gloss
        tsupertype ancestors
      • All of its recorded
        Gloss
        tqualifier
        values and/or
        Gloss
        tdefining characteristics
        , irrespective of whether they are shared by its most proximate
        Gloss
        tprimitive
        supertypes.

If the retrieval criteria are expressed in a similar form, a relatively simple

Specref
RefTypefield
tquery
can interrogate the record for all entries with a matching set of
Gloss
Spacetrue
tprimitive
Gloss
tConcepts
and specified characteristics.