Opasnet base structure

This page is a knowledge crystal of subtype method. The page identifier is Op_en1913
Moderator:Nobody (see all) Click here to sign up.
Upload data {{#opasnet_base_link:Op_en1913}}

Result database is a storage and retrieval system for variable results. It is basically an SQL database with the following functionalities:

1. Storage of results of variables with uncertainties when necessary, and as multidimensional arrays when necessary.D↷
2. Automatic retrieval of results when called from the collaborative workspace or other platforms.
3. Description and handling of the dimensions that the variables may take.
4. Storage and retrieval system for items that are needed to calculate the results of variables.
5. A platform for performing computer runs to update the results of variables.
6. Follow-up of the linkages between variables, the data about a particular variable, and the computing formula of the variable, in respect to their impact on the variable result.
7. Follow-up of the age and validity of the content based on the previous point.
8. A platform for planning computer runs based on the update need, CPU demand, and CPU availability.

Functionalities of the result database

Storage and retrieval of results of variables

The most important functionality is to store and retrieve the results of variables. Because variables may take very different forms (from a single value such as natural constant to an uncertain spatio-temporal concentration field over the whole Europe), the database must be very flexible. The basic solution is described in the variable page, and it is only briefly summarised here. The result is described as

  P(R|x1,x2,...) 

where P(R) is the probability distribution of the result and x₁ and x₂ are defining locations where a particular P(R) applies. A dimension means a property along which there are multiple locations and the result of the variable may have different values when the location changes. In this case, x₁ and x₂ are dimensions, and particular values of x₁ and x₂ are locations. A variable can have zero, one, or more dimensions. Even if a dimension is continuous, it is usually operationalised in practice as a list of discrete locations. Such a list is called an index, and each location is called a row of the index. In the general information structure of the new risk assessment method, dimensions are Classes with a special purpose. An index can be thought of as a variable that inherits its plausible range from a dimension (class).

Uncertainty about the true value of the variable is operationalised as a random sample from the probability distribution, in such a way that the samples are located along an index Sample, which is a list of integers 1,2,3...n, where n=number of samples.

The dimensions of a variable are determined by the parent variables (by inheritance) and the formula used to calculate the result. Thus, there is not a place where the dimensions of a particular variable are explicitly asked for. In addition, the indices (as operationalisations of dimensions) are NOT properties of variables but of risk assessments. This may sound unintuitive, but the reasoning is that indices are just practical ways to handle dimensions, and these practical needs may change from one assessment to another.

The tables Variable and Result contain the result data. In addition, Location, Dimension, Index, and Rows contain data about the dimensions and indices used. These tables together offer the functionalities of data storage and retrieval, and handling of multidimensionality and uncertainty.

Calculation of the updated results

The result of a variable can be calculated when four things are known:

1. The list of of upstream variables (parents) (Definition/causality attribute),
2. The results of the parent variables,
3. The data used to derive the result (Definition/data attribute), and
4. The formula used to calculate the result based on the items above (Definition/formula attribute).

The three sub-attributes of the Definition are represented by three tables in the result database: Causality, Formula, and Data. In addition, the results of the parents can be obtained from the Result table. The variable transfer protocol is used to extract these data from the result database, send them to an external software such as R to calculate the result, and store the calculated result into the Result table of the database. The technical solutions to do this in practice have to be developed.

When a variable result is calculated, the computing software must know, which indices must be used with which variables. This can be automatically resolved using the following reasoning algorithm.

• Make a list of all unfinished risk assessments.
• Make a list of all indices in these risk assessments.
• Compile all indices of a particular dimension into one large "super-index" with all the locations.
• Use these "super-indices" in the calculations.
• Apply a particular "super-index" for a particular variable, if that variable has the dimension in question.

A wild use of occasional indices is discouraged, because they cause heavy computing needs with little benefit. Therefore, there should be a "standard risk assessment" that is constantly kept unfinished. It would then contain recommended indices for all major dimensions. This way, at least the standard indices are always used in computations, and the need for users to develop their own indices is smaller.

When the new results are stored in the database, the old results of the variables are deleted. The different versions of the variable results are NOT permanently stored anywhere. However, when a risk assessment report is created using the reporting tool, the result distributions used for that report are stored, together with the definitions and other data about all variables. Thus, a full copy of everything that relates to a particular assessment can be downloaded and stored outside the result database.

Follow-up of validity

The result of a variable is valid since its update until something that affects its content (i.e., the four things listed above) changes. Therefore, there must be a system that follows what things these are for a particular variable, and whether they have changed since the last calculation of the variable result. When the data in Causality, Formula, and Data tables is combined with the data of the dates when the parent variables were run, it can be automatically concluded whether the variable is valid or not. If the variable is older than its determinants, there is a need to recalculate the result. This cannot be done fully automatically, because some variables are probably being actively edited, and this would create a constant need to update everything downstream. In addition, some complex variables may take even weeks to compute.

Therefore, there should be a planning system for result updates. This can easily be done by adding tables Run and Run_list to the database. These tables contain information about the runs that have been performed or are being planned to be performed. The user can add variables to and delete them from the lists of planned runs. The needs for updating can be combined into practical collections of variables, given their connections, computer time needed, and computer time available. Then, when the task has been defined and the resources are available, a computer run can automatically be performed.

Suggested techniques to get started

MySQL:

The current idea is to describe the variables in Mediawiki, which is a text-based software. It would therefore become very difficult to operate these functionalities from there. Instead, if we store the data into the most convenient way, it can be effectively utilised. The most convenient way is to use an SQL database, which is the standard for large databanks. Among all SQL software, MySQL is the best due to several reasons:

• It is freely available open access software.
• It is easy to use.
• It has powerful functionalities.

To make this work out, we need a variable transfer protocol so that the result of a variable can be retrieved either automatically by a calculating software, or manually by the user who wants to explore the result. Fancy presenting software can be built on top of the database, so that the user does not see huge lists of numbers, but nice distributions instead. The development of this software is, again, technically straightforward, because:

• It is only communicating with the MySQL database, except some launch codes must be placed in other parts of the toolbox. Thus, the development can easily be decentralized.
• Something applicable probably exists in the open code world.
• It is not needed in the early life stages of the toolbox.

A suggested table and column structure for the database

Variable Information about variable attributes and validity Columns Var_id* (identifier of the variable) Var_name (variable name as in Mediawiki) Var_scope (variable scope as in Mediawiki) Var_unit (variable unit as in Mediawiki) Validity_date (the date when the variable last was valid [1.1.2100 if it is currently valid]) Run_id (the run that produced the current results of the variable) Run_time (CPU time that was needed for this variable during the last run)

Result All results are stored in this table. Each value of a result of a variable has an own row. Columns Result_id* (identifier of the row in this table) Var_id (identifier of the variable) Result (the actual value of the variable) Sample (the row in the uncertainty index Sample. Use 0, if the result is deterministic.)

Location The location of the result along a particular dimension. Columns Result_id* Dim_id* Location	Dimension Information about dimensions Columns Dim_id* (Dimension identifier) Dim_name (Dimension name) Dim_scope (Dimension scope) Dim_unit (Dimension unit) Dim_definition (Dimension definition) Dim_result: (Dimension result: the range of plausible values, such as "non-negative real number", "positive integer", or an exhaustive list of labels)
Index Information about indices Columns Ind_id* (index identifier) Ind_name (index name) Dim_id (dimension identifier)	Rows Information about rows of indices Columns Ind_id* (index identifier) Row_number* (the number of this row in the index) Location (the location along the dimension of this row and index)
Risk_assessment Attributes of a risk assessment Columns RA_id* (risk assessment identifier) RA_name RA_scope RA_started (date when the risk assessment was started) RA_finished (date when the risk assessment was finished)	RA_vars Defines the variables used in a risk assessment Columns RA_id* (risk assessment identifier) Var_id* (variable identifier)
RA_indices Defines the indices used in a risk assessment Columns RA_id* (risk assessment identifier) Ind_id* (index identifier)

Causality Defines the parents in the causal chain Columns Var_id* Causality_date (date when the parent list was last changed) Parent_id* (var_id of a parent variable)	Formula Defines the formulas of the variables Columns Var_id* Formula_date (date when the formula was last changed) Software* (name of the software able to run the formula) Formula (software code)
Data Defines the data of the variables Columns Var_id* Data_date (date when the data was last changed) URL* (location of the data file)	Run Information about the computer runs Columns Run_id* (the identifier of the computer run) Run_date (when the run was actually performed successfully) Run_who (who performed/will perform the run) Run_method (what method was/will be used in the run) Planned_run_date (the estimated date for the run)
Run_list List of variables in a run Columns Run_id* (the identifier of the computer run) Run_order* (the order in which the variables will be computed) Var_id (the identifier of the variable)

^* This column or these columns together uniquely identify the row in the table

---

Result database is for storing variable results in a way that they can be used independently of the assessment they were created in.

Possible uses of the database

Making value-of-information analyses

Value of information (VOI) is a decision analysis tool for estimating the importance of remaining uncertainty for decision-making. For detailed description, see Value of information. Result database can be used to perform a large number of VOI analyses, because all variables are in the right format for that: as random samples from uncertain variables. The analysis is done by optimising an indicator by adjusting a decision variable so that the variable under analysis is conditionalised to different values. All this can in theory be done in the result database by just listing the indicator, the decision variable, and the variable of interest. Practical tools should be developed for this. After that, systematic VOI analyses can be made over a wide range of environmental health issues.

The improvement of the quality of a variable in time

All results that have once been stored in the result database remain there. Although the old results are not interesting for environmental health assessments after the updated result has been stored, they can be very interesting for other purposes. Some potential uses are listed below:

• The informativeness and calibration (see performance) can be evaluated for a single variable in time against the newest information.
• Critical pieces of information that had made major contribution to the informativeness and calibration can be identified afterwards.
• Large number of variables can be assessed and e.g. following questions can be asked:
  • How much work is needed to make a variable to have reasonable performance for practical applications?
  • What are the critical steps after which the variable performance is saturated, i.e., does not improve much despite additional effort?

Some useful syntax

http://www.baycongroup.com/sql_join.htm

---

• Result database connection module for Analytica: for writing variable results into the database. This requires a password.
• Result database reader module for Analytica: for reading variable results into the database.

• For SQL used by RDB reader.ANA and RDB connection.ANA, see the respective pages.

Useful queries that are not (yet) part of a model of procedure

List all dimensions that have indices, and the indices concatenated:

Select Dim_name, dim_title, dim_unit, Group_concat(Ind_name order by ind_name separator ', ') as Indices 
from Dimension, `Index`
where Dimension.dim_id = `Index`.Dim_id
group by Dim_name
order by Dimension.dim_id

List all indices, and their locations concatenated:

Select Dim_name, Dim_title, Dim_unit, Ind_name, Group_concat(Location order by row_number separator ', ') as Locations 
from `Index`, Location, Rows, Dimension
where `Index`.ind_id= Rows.ind_id and Rows.loc_id = Location.loc_id and `Index`.dim_id = Dimension.dim_id
group by Ind_name
order by Dim_name, `Index`.ind_name

List all variables and their runs, and also list all dimensions (concatenated) used for each variable for each run.

SELECT Var_id, Run_id, Var_name, Var_title, GROUP_CONCAT(Dim_name SEPARATOR ', ') as Dimensions, n, Run_method
FROM
   (SELECT Loc_of_result.Var_id, Run_list.Run_id, Var_name, Var_title, Dim_name, n, Run_method
   FROM Loc_of_result, Run_list, Run, Variable, Location, Dimension
   WHERE Loc_of_result.Result_id = Run_list.Result_id 
   AND Run_list.Run_id = Run.Run_id
   AND Loc_of_result.Var_id = Variable.Var_id
   AND Loc_of_result.Loc_id = Location.Loc_id 
   AND Location.Dim_id = Dimension.Dim_id
   GROUP BY Dimension.Dim_id, Loc_of_result.Var_id, Run_list.Run_id
   ORDER BY Loc_of_result.Var_id, Run_list.Run_id) as temp1
GROUP BY Var_id, Run_id

Other queries

This query was used to transform the Var_id data from the table Result to Loc_of_result. This was a one-time operation that is recorded for historical interest only.

UPDATE Loc_of_result, 
  (SELECT Variable.Var_id, Var_name, Loc_of_result.Loc_id, Loc_of_result.Result_id
   FROM Variable, Loc_of_result, Result
   WHERE Variable.Var_id = Result.Var_id and
   Loc_of_result.Result_id = Result.Result_id
   GROUP BY Loc_of_result.Result_id, Loc_of_result.Loc_id) as temp1
SET Loc_of_result.Var_id = temp1.Var_id
WHERE Loc_of_result.Loc_id = temp1.Loc_id and
   Loc_of_result.Result_id = temp1.Result_id