Define Distributed Attributes

To spread the distributed attributes, identify the elements and attributes required, create, define and connect elements:

• Create bound elements

• Create attributes for bound elements

• Create the distributed attribute schema

• Define binding elements

• Connect bound elements to binding elements.

Create Bound Elements

The task only differs from the creation of a regular User Defined Element Type (UDET) element in one aspect, and that is that the UDET intended for use as bound attribute group must be based on the XPITEM element type.

To create bound elements, the UDETs to be used as bound attribute groups must be created, these UDETs must be defined with XPITEM as their basetype, then the attributes must be created. Refer to User Defined Element Types for further information on the creation of a UDET element.

Create Attributes for Bound Elements

The attributes can be defined as any regular User Defined Attribute (UDA), no special considerations need to be taken. Refer to User Defined Attributes for further information on the creation of a UDA.

Create Binding Elements

A binding element can be any system defined element type or UDET. Engineering items for use in AVEVA Tags must be UDETs with a Base Type of ENGITE. Refer to User Defined Element Types for further information on the creation of a UDET.

Distributed Attributes Hierarchy

Before distributed attributes can be used, the top level XPIWLD elements must be created in the required databases for the bound elements to be created in. These must be all of the XPIWLDs identified by the DSXDST elements for the distributed attributes and can be created with AVEVA Administration or another application module.

Create Distributed Attribute Schema

To create the distributed attribute schema, elements must be linked and bound then the database where the bound elements are to be created and stored in must be defined:

• Link binding and bound elements

  • Create DSXSCH

  • Create DSXOWN

  • Create DSXMBR

• Define which database the bound elements are created and stored in

  • Create DSXHOM

  • Create DSXTST

  • Create DSXDST

It is assumed that the two administrative levels, DSXWLD and DSXGRP elements have been navigated to or have been created.

Create DSXSCH Element

DSXSCH elements represent distributed attribute schema and consists of a name and an optional default home reference. The default home reference specifies the location that the bound elements are created in. The location can be overridden at lower levels in the schema.

Create DSXOWN Element

DSXOWN elements represent the binding element type definition, define the element type that may be extended by attributes. The definition contains an element list which designates the element type and a default home reference that specifies the hierarchy where the Bound elements are created.

Create DSXMBR Element

The DSXMBR element binds the distributed attributes to the binding element defined by the owning DSXOWN element. The definition specifies which XPITEM based UDETs can be used as attributes for the specified owner. There is a cardinality definition available that defines the minimum and maximum number of each of the attributes that may be created. A -1 in the maximum definition represents an infinite number. It also contains an allocation reference that might override anything defined at schema or owner level. The default Home definition is the location where attributes are created and managed.

Create DSXHOM Element

The DSXHOM element represents the actual default home, for example: creates the top-level elements where the attribute groups are created. The default home destination contains a string or ID expression that evaluates the name or ID of the default home to be used.

Create DSXTST Element

The DSXTST element defines the default home value as a text string. It also contains a test that must yield true upon evaluation to consider this default home as valid.

Create DSXDST Element

The DSXDST element denotes the default home value as a text string. It contains a test that must yield true upon evaluation to consider this default home as valid.

Distributed Attributes Graphical View

To view relationships between a UDET and its distributed attribute element types in the Graphical View window of the Lexicon module. Select the required DSXOWN or DSXMBR element in the Dictionary Explorer, then on the Home tab, in the Display group select Graphical View to display the graphical view for the selected element.

The central node is the Binding Element, the list in this node displays the elements to which the distributed attributes can be bound. The list is populated with the element types from the ELEL attribute of the DSXOWN element (:VALVTAG in this case).

The bound element types (based on XPITEM) display as nodes that depend on the binding element. The arrangement of nodes in the distributed attributes view window follows the same rules as the UDA graphical view window, when there are less than 20 bound nodes, the view is arranged in spider layout, otherwise the list layout displays.

Cases

Datasheets can display a group of attributes in a table with alternative sets of values according to different design or operating cases.

In order to use cases, a Distributed Attributes data model must be defined, with the set of attributes required for each case to be grouped on a single bound element type (XPITEM). The Distributed Schema can then be set cardinality on this bound element type to define the number of cases that can be stored against the binding element type (ENGITE). Thus a Tag can have a number of alternative sets of the same attributes associated with it.