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Proposal for UIML2 Shorthand

Send comments to Marc Abrams
(mailto:abrams@uiml.org)

11 October 2000

Abstract

Describing a user interface in UIML2 can produce fairly verbose documents, compared to other markup languages (e.g., HTML). Proposed here is a shorthand notation called UIML2 Shorthand that can be mechanically mapped to UIML2.

Motivation

The reason that UIML2 can be verbose is illustrated by the following <structure> element, which creates a Java AWT Frame containing a Java AWT Label:

 

<structure>

<part name="TopHello" class="Frame">

<style>

<property name="rendering">Frame</property>

<property name="title">Example UI</property>

<property name="resizable">true</property>

<property name="layout">java.awt.FlowLayout</property>

<property name="background">blue</property>

<property name="foreground">white</property>

<property name="size">500,100</property>

<property name="location">100,100</property>

</style>

<part name="L" class="Label">

<style>

<property name="text">Sample label.</property>

</style>

</part>

</part>

<structure>

The fragment above requires 12 lines to describe the Frame, and 5 lines to describe the label. Moreover, for complex documents requiring many interface components, the <structure> element can become difficult to read.

Proposed Syntax for UIML2 Shorthand

The same example in UIML2 Shorthand would look like this:

 

<structure>

<Frame name="TopHello" title="Example UI"

resizable="true" layout="java.awt.FlowLayout"

background="blue" foreground="white"

size="500,100" location="100,100">

<Label name="L" text="Sample label."/>

</Frame>

<structure>

The syntax above has several advantages over the original UIML2 syntax:

  • The description is more intuitive: the tags are things like Frame and Label.
  • The description is more concise than UIML2.
  • The syntax can be mechanically translated into UIML2, so that this proposed change introduces no compatibility problems with existing software for UIML2. A preprocessor can expand UIML2 Shorthand into UIML2.

Specification of Transformation Rules

A UIML2 Shorthand document must satisfy the following requirements.

 
  1. UIML2 Shorthand syntax is identical to UIML2 for all UIML2 language elements other than the children of <structure>.
  2. All children of <structure> in a UIML2 document are transformed as follows. Given an element C in the UIML2 Shorthand document
    3.

    <C name="N" P1="V1" ... Pn="Vn">

    ...

    </C>

    the equivalent UIML2 fragment is

    <part class="C" name="N">

    <style>

    <property name="P1">V1</property>

    ...

    <property name="Pn">Vn</property>

    </style>

    ...

    </part>

  3. In UIML2 Shorthand, no child element of <structure> can have the tag name part.
    4.

Equivalency of UIML2 Shorthand and UIML2 Documents

A UIML2 document containing a <part> with a class attribute of "part" cannot be represented as a UIML2 Shorthand document (due to item 3 in section "Specification of Transformation Rules"). Otherwise, all UIML2 documents have an equivalent representation in UIML2 Shorthand, and vice versa.

UIML2 Shorthand to UIML2 Converter

To use UIML2 Shorthand, one requires a converter program. The program reads a UIML2 Shorthand document as input, validates the document if a DTD or XML Schema is present in the input file, translates the document to the UIML2 syntax, and writes a UIML2 document as output. A converter program must include in the output UIML2 document the name of the DTD or XML Schema whose syntax is used by the converter (e.g., http://uiml.org/dtd/UIML2_0d.dtd).

Use of DTDs and XML Schemas with UIML2 Shorthand

There is no fixed set of tags used within the <structure> element of a UIML2 Shorthand document. Consequently it is impossible to create a single DTD or XML Schema to be named in a UIML2 Shorthand document.

The reason is that the UIML2 language is always used with a vocabulary defined outside UIML2. For example, there are vocabularies for Java JFC, HTML, WML, generic toolsets, and so on. Each vocabulary specifies possible values for the class attribute of the part element in UIML2. For example, a vocabulary for Java JFC might include class names of "Frame," "Menu," and "List." In UIML2 Shorthand, these class names become elements <Frame>, <Menu>, and <List>. Any DTD or XML Schema used with UIML2 Shorthand would therefore be dependent on the vocabulary used with UIML2.

Given this, one way to use UIML2 Shorthand is to create a DTD or XML Schema for every vocabulary proposed for UIML2. A UIML2 Shorthand file can then include the proper DTD or XML Schema file, and the converter program (see "UIML2 Shorthand to UIML2 Converter" above) could then validate the UIML2 Shorthand file.

Note that a single UIML2 Shorthand document might use multiple vocabularies. For example, one UIML2 Shorthand document might be designed to render to HTML and WML, and therefore use both the HTML and WML vocabularies. In this case one would have to use a DTD or XML Schema that was the union of the DTDs or XML Schemas for the HTML and WML vocabularies.

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