filterprop

5reg

filterprop

A surface filter that uses basic properties

Content Model
    filterprop ::= (&xml-tag;*,
                    &packetsyn1;
                    &packetsyn2;
                    &packetsyn3;
                    &packetsyn4;
                    &packetsyn5;*)
Attributes
Name | Type
`compact` | `CDATA`
`euler` | `CDATA`
`orbl` | `CDATA`
`realbdry` | `CDATA`
&packetattrlist2col;

&eltaddedver;7.0

## Description

This represents a property filter packet, one of the many types of packet that together form the packet tree that a user sees when they open a ®ina; data file, and also one of the different types of filter that users can create to refine a set of normal surfaces.

A property filter filters normal surfaces by examining basic topological properties such as orientability and Euler characteristic.

The specific constraints imposed by this filter are stored in the optional attributes `compact`, `euler`, `orbl` and `realbdry`. If this filter has several such attributes, a surface must satisfy all of the corresponding constraints in order to be accepted by this filter. (These attributes replace the deprecated &xml-compact-filter;, &xml-euler-filter;, &xml-orbl-filter; and &xml-realbdry-filter; elements, which were used with &xml-filter; in older versions of ®ina;.)

&packetchilddesc;

### Parents

&packetparents;

### Children

Element `filtercomb` has no children that are specific to property filters.

&packetchildren;

## Attributes

The following attributes are specific to combination filters:

`compact`

- Constrains the compactness of a surface. The following values are allowed:

  - `TF` signifies that the surface may be either compact or non-compact, i.e., no constraint is imposed.

  - `T-` signifies that the surface must be compact.

  - `-F` signifies that the surface must be non-compact.

  - `--` signifies that the surface must be neither compact nor non-compact, i.e., no surfaces are accepted.

  This constraint is optional; if not specified, it defaults to `TF` (i.e., there is no constraint on compactness).

`euler`

- Constrains the Euler characteristic of a surface. This attribute holds a comma-separated list of integers. A surface will satisfy this constraint if its Euler characteristic belongs to the list.

  The list of integers must not contain any whitespace.

  This constraint is optional; if it is not specified or if the list is empty, then all Euler characteristics are allowed (i.e., there is no constraint on Euler characteristic).

`orbl`

- Constrains the orientability of a surface. The following values are allowed:

  - `TF` signifies that the surface may be either orientable or non-orientable, i.e., no constraint is imposed.

  - `T-` signifies that the surface must be orientable.

  - `-F` signifies that the surface must be non-orientable.

  - `--` signifies that the surface must be neither orientable nor non-orientable, i.e., no surfaces are accepted.

  This constraint is optional; if not specified, it defaults to `TF` (i.e., there is no constraint on orientability).

`realbdry`

- Constrains the boundary of a surface. The following values are allowed:

  - `TF` signifies that the surface may either have real boundary or may not, i.e., no constraint is imposed.

  - `T-` signifies that the surface must have real boundary.

  - `-F` signifies that the surface must not have real boundary.

  - `--` signifies that the surface must neither have real boundary nor not have real boundary, i.e., no surfaces are accepted.

  This constraint is optional; if not specified, it defaults to `TF` (i.e., there is no constraint on the boundary).

&packetattrdesc;

## Example

The following &xml; snippet represents a filter that accepts discs and annuli.

    <filterprop orbl="T-" compact="T-" realbdry="T-" euler="0,1"/>