Architecture Workgroup

P1. Purpose

P1.1 Introduction

Xlink is an XML based language for relating information. It is more flexible than ID IDREF IDREFS method used in Versions 1 and 2 of MISMO Architecture. It is more extensible than the xs:key xs:keyref approach used by Commercial MISMO. However it‘s use is not incompatible with either the Residential or Commercial legacy designs.

P1.2 Audience

1. MISMO Workgroup members developing MISMO messages.
2. Designers and users of systems that create and consume the XML instance documents used in Real Estate Finance transactions.
3. Technical or business professionals wishing to evaluate MISMO specifications.

P1.3 Terminology

1. MUST - This word,or the terms “REQUIRED” or “SHALL”, mean that the definition is an absolute requirement of the specification.

2. MUST NOT - This phrase, or the phrase “SHALL NOT”, mean that the definition is an absolute prohibition of the specification.

3. SHOULD - This word, or the adjective “RECOMMENDED”, mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.

4. SHOULD NOT - This phrase, or the phrase “NOT RECOMMENDED” mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label.

5. MAY - This word, or the adjective “OPTIONAL”, mean that an item is truly optional.

P1.4 Document Status

P1.5 Rationale for this MEG

C1.1 Guidelines

Ref	Guideline
36.1	1:1 relationships SHOULD be expressed by containment.
36.1.1	All data points MUST have a 1:1 relationship with the container that holds them.
36.1.2	Relationships between containers MAY be expressed by a RELATIONSHIP container. Some 1:1 relationships are between containers. For example two PARTY containers can have a co-applicant relationship that is expressed using xlink.
36.2	1:Many relationships SHOULD be expressed by containment.
36.2.1	A container MAY have a child with a plural noun name. For example EMPLOYERS may be a child of BORROWER. The cardinality of EMPLOYERS is 0:1. The cardinality of EMPLOYER, which is a child of EMPLOYERS, is 0:Many.
36.2.2	The 1:Many relationship MAY be between containers. For example a BORROWER may have many ASSETS. In this case the relationship is expressed in the RELATIONSHIP container.
36.3	Many:Many relationships MUST be expressed with xlink using the RELATIONSHIP elements.
36.3.1	Relationship SHOULD be expressed with three facts: From, To, Arcrole. Each of these are elements in the Xlink namespace as defined by the W3C http://www.w3.org/TR/xlink/.
36.3.2	The RELATIONSHIPS container SHALL be limited to the following locations: child of DEAL, child of BUNDLE, child of DOCUMENT, and child of MESSAGE. The scope of each of these MUST be limited to items that are siblings of the parent RELATIONSHIPS container or descendants of those siblings.
36.3.3	When creating instance documents implementers MAY select to provide only one direction arcs
36.3.4	Arcroles WILL be managed in the LDD as simple types.
36.3.5	xlink:arcrole values WILL be the URI form of the LDD simpleType.

C2 Additional Information - Examples

Example of 36.1

Data point FirstName child of NAME container

<NAME>
    <FirstName>Alice</FirstName>
</NAME>

Example of 36.2

All of these are valid XML instance documents

Example A, a Borrower has two Aliases

<BORROWER>
    <ALIASES>
        <ALIAS>
            <NAME>
                <FirstName>Alisson</FirstName>
            </NAME>
        </ALIAS>
        <ALIAS>
            <NAME>
                <FirstName>Ali</FirstName>
            </NAME>
        </ALIAS>
    </ALIASES>
</BORROWER>

Example B, a Borrower has no Alias

<BORROWER>
    <ALIASES/>
</BORROWER>

Example C, a Borrower has no Alias

<BORROWER/>

Examples of 36.3

Example A
Two directional relationships from Asset to Borrower and from Borrower to Asset. Note that xlink:arcroles will be URI but are shortened here.

<?xml version="1.0" encoding="UTF-8"?>
<DEAL xmlns="http://mismo.org/residential/2009/schemas"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink"
    xsi:schemaLocation="http://mismo.org/residential/2009/schemas file://V3_Reference_Model_DRAFT_20081212.xsd"
    type="resource">
    <ASSETS>
        <ASSET type="resource" xlink:label="Asset1">
    </ASSET>
    </ASSETS>
    <PARTIES>
        <PARTY>
            <ROLES>
                <ROLE>
                    <BORROWER type="resource" xlink:label="Borrower1">
                    </BORROWER>
                </ROLE>
            </ROLES>
        </PARTY>
        <RELATIONSHIPS/>
    </PARTIES>
  <RELATIONSHIPS>
                <RELATIONSHIP type="arc" xlink:from="Asset1" xlink:arcrole="IsOwnedBy" xlink:to="Borrower1"/>
                <RELATIONSHIP type="arc" xlink:from="Borrower1" xlink:arcrole="IsOwnerOf" xlink:to="Asset1"/>
  </RELATIONSHIPS>
</DEAL>

Example B
SimpleType representation of Asset Onwership

<xs:simpleType name="AssetOwnership">
    <xs:restriction base="xs:string">
        <xs:enumeration value="IsOwnerOf"/>
        <xs:enumeration value="IsOwnedBy"/>
    </xs:restriction>
</xs:simpleType>

Example C
URI representation of Asset Ownership

• urn:org:MISMO:residential:2009:LDD:AssetOwnership:IsOwnerOf
• urn:org:MISMO:residential:2009:LDD:AssetOwnership:IsOwnedBy

Metadata

M1. Metadata

Element	Description
Title	MEG0036 Use of Xlink To Manage Relationships
Identifier	MEG0036
Category	Baseline
Date Created	1/15/2007 7:15:00 AM
Last Updated	4/24/2009 01:26:00 PM
Rights	Copyright of MISMO. All rights reserved.

M1.1 Release History

Date	Release	Comments
1/16/2007	.01	Initial Version
1/15/2009	.02	Draft revision
1/20/2009	.03	Added examples on Xlink
1/21/2009	.04	Formatted per MEG template, minor corrections, and updated examples.
4/24/2009	.05	Updated based on 4/24 D3 call.

M1.2 Known Issues or Omissions

None

M1.3 Contacts

Name	Organization	Contact Details
MISMO Staff	MISMO	info@mismo.org

M1.4 References

Title	Location
RFC2119	http://rfc.net/rfc2119.html
W3C Schema Structure	http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/structures.html
Xlink	http://www.w3.org/TR/2001/REC-xlink-20010627/

Comments

2009

Terms

T1. Terms and Conditions

T1.1 Disclaimer

MISMO accepts no liability for the accuracy, adequacy, or completeness of the information contained in this MISMO Engineering Guideline (MEG).

T1.2 Reproduction

Material in this MEG may be reproduced free of charge without obtaining explicit permission from MISMO, provided that the source is acknowledged, the document title given, and the material is used in context.

T1.3 Copyright

©2008 MISMO. All material in this MEG is the property of MISMO. All Rights Reserved.