The visual specification creation process

The visual specification creation process provides you with several options for designing a new set of calculated representations or calculated fields for a product specification. The process itself, however, begins with the decision of whether to create both calculated representations and calculated fields or just one of those components.

The process for designing a visual specification is as follows:

• Create a specification for your rules.
• Create rules for calculated representations or calculated fields as necessary.

Specifications

Specifications are ways to group calculated representations and fields so they correspond with a product specification or other symbology requirements you may have. You can create specifications that correspond to hard-copy and electronic products.

You have to set the following to create specifications:

• Table location—Where the information related to specifications is stored. The table can be stored in a geodatabase you specify.

  The product library geodatabase is recommended if one is being set up and used in other workflows. The information in the specifications table is used to associate your rules, stored in the rules table, with the appropriate specification.

• Name—The name you have defined for the specification. This can correspond with a product specification or a different grouping you would like to use for the rules you are going to define.
• Description—A brief description of the specification you are creating. If you have used an acronym as the specification name, the description can be the definition of the acronym.
• Preserve free representations—This check box resides on the Layer Properties dialog box. When checked, visual specification calculation will not overwrite existing free representations. A free representation is a rule associated with a single feature.

Calculated representation specification rules

Calculated representations allow you to use attributes to determine the way features are symbolized. The representations are grouped based on specifications, which can be based on actual data models you are using.

The calculated representation creation process is divided into several steps, as outlined below.

Creating a new representation

A representation is related to a feature class and is a means of storing a group of RuleIDs to symbolize features. By default, the representation name is <feature layer name>_<specification name>. This indicates which group of rules pertains to a layer that is associated with a specification.

Learn more about understanding representations

When you create the representation, you have two options for determining the way a feature's geometry is changed:

• Store change to geometry as representation override—Leaves the source feature intact and stores any changes with the explicit override fields
• Change the geometry of the supporting feature—Changes the geometry of the source feature based on the representation rule

Learn more about managing the geometry editing behavior settings

Creating a calculated representation specification rule

Calculated representation specification rules contain descriptive information to identify the rule as well as the Structured Query Language (SQL) statements and Visual Basic Scripting Edition (VBScript) expressions that define the symbolization for the statement. The SQL statements allow you to choose the attributes you want to use from both feature layers and stand-alone tables. For example, you can construct a query in which you include features where the Name field in a feature class is equal to the Full_Name field in a stand-alone table.

The definition of the rule can be extended with a VBScript to refine the symbols used for these features. For example, you can use one symbol to represent cities with populations between 1,000 and 50,000 and larger symbols to represent cities with populations between 50,001 and 100,000 using if…then statements.

The symbol can be chosen from any style that contains representation rules. If the style does not contain representations, it still appears on the Representation Rule Selector dialog box but does not have any symbols that can be chosen.

When the specification rule is created, you can choose to update the feature class with the symbols when changes are applied.

Defining overrides for the fields

In addition to the basic rule for the calculated representation, you can also define overrides for the representation rule. This allows you to create conditions in which the symbol size or other properties change depending on values in a specified field.

Remarque :

Only fields with a Double data type can be used as override fields.

Calculated field specification rules

Calculated fields allow you to determine the appearance of labels and annotation or basic data type values based on attributes you select. The fields are grouped based on the specification you choose.

The calculated field creation process is divided into several steps, as outlined below.

Creating a calculated field specification rule

Calculated field specifications rules contain descriptive information to identify the rule as well as the Structured Query Language (SQL) statements and Visual Basic Scripting Edition (VBScript) expressions that define the labels or annotation that are going to be displayed. The SQL statements allow you to choose the attributes you want to use from both feature layers and stand-alone tables. For example, you can construct a query in which you include features where the Name field in a feature class is equal to the Full_Name field in a stand-alone table. With calculated fields, you also define a VBScript that indicates which fields can be used to determine the field values.

Specifying a field for the calculated fields

When the calculated fields are created, you have the option of overwriting values in an existing field or creating a new field for the calculated values. When you create a new field, the values that result from the SQL statement and VBScript expression populate the field.

Status of calculated representations and fields

As calculated representations and calculated fields are created, there are different symbols displayed next to them to indicate their status. The table below shows each of the symbols with a brief description.

Status	Symbol	Description
New Calculated Representation		A new representation or field has been added to the specification.
Calculated Representation		A feature class representation or field exists.
Virtual Calculated Representation/Field		A representation or field exists in the specification, but it does not currently exist on the layer's feature class.
Current Calculated Representation		The representation or field is currently set to the layer for the specification.
Different Calculated Representation		The representations or field properties that exist in the specification are different from the representation or field properties on the layer's feature class.

Status symbols for calculated representation and fields

Calculating visual specifications

This is the last step in the creation process. Calculating a visual specification applies representation rules and generates the text strings in calculated fields. There are two ways to do this:

1. Execute the Calculate Visual Specifications geoprocessing tool.
2. Check the Update Feature Class(es) check box on the Layer Properties dialog box on the Calculated Representations tab or the Calculated Fields tab. If more than one set of specifications is associated with the same data, you can decide to only update columns associated with individual specifications.

   Astuce:

   To make the Calculated Representations and the Calculated Fields tabs visible in the Layer Properties dialog box, check the Display Calculated Representations and Calculated Fields tab check box on the Visual Specifications dialog box.