Creating a Function Catalog

Procedure

Create a function catalog file. For example, my.function.catalog. Create the function descriptors as shown in the following sample:

   <function-descriptors name="my-functions">
      <function-descriptor name="My.AVG"
     category="my category" multivalued="false" 	      implclass="com.tibco.rta.runtime.metric.functions.MyMetric"
      datatype="DOUBLE" description="My metric function">
   </function-descriptor>

Table 1. Function Descriptors Properties
Property Name	Description
name	Name of the function
category	The category name
multivalued	Indicates whether or not the function is single-valued or multivalued. The default value is `false`. Remember that for a multivalued function, all values must be of the same datatype.
implclass	To create custom metric function, you should extend either `SingleValueMetricFunction` or `MultiValueMetricFunction`. For more information about the API, refer to the TIBCO Service Performance Manager Java API reference pages.
datatype	Datatype of the metric. For example, the datatype of `AVERAGE` is generally be a `double`.
description	Description of the metric function

Create the function parameters as shown in the following example:
```
    <function-params>
    <function-param id="PARAM1" datatype="LONG" ordinal="0"
     description="Measuable Quanitity to be averaged" />
    </function-params>
```
Specify the function parameters, data types, and the ordinal position. The parameters specified here are bound to the fact attributes in the <product_name>_schema.xml. For example, the ID specified for the parameter is used in the schema to bind the parameter to the fact.

Binding Function Parameters to the Schema

Each metric can store some contextual data for future reuse. The context definition is also used by the database schema generator to generate columns in the metric tables. For each metric, the associated context is stored in these columns in the database. Create the function context as shown in the following example:

    <function-context>
         <function-param id="count" datatype="LONG" ordinal="0"
         description="" />
         <function-param id="sum" datatype="DOUBLE" ordinal="1"
       description="" />
    </function-context>
  </function-descriptor>
</function-descriptors>