The algorithm described in this chapter provides an approach to record linkage based on the relations between multiple records. This allows for a strongly reduced dependence on string similarity metrics. Results on the benchmark set show that the amount of errors in a practical setting remains limited. Further analysis indicates that a significant part of the errors is caused by missing or incorrect data, although it is difficult to differentiate between data issues and method design flaws. However, this method could be considered as complementary to other record linkage approaches to increase matching coverage.
This approach is an example of collective entity resolution, which has received an increasing amount of research attention in recent years. Compare for example Figure 7.2 to [10, Figure 1], in which similarity of references as well as overlap in relations is used for record linkage. In the terminology of [10] the basic linkage step illustrated in Fig- ure 7.2c can be considerednaive relational entity resolution, given that the decision to
merge the 1846 marriage certificate with the two hypothetical marriage certificates as- sociated to the 1846 and 1849 birth certificates is based both on the similarity of the names of the marriage couple and the parent couples, which is an attribute of the records themselves, but also on the similarity of the date, which is an attribute of the hypothetical marriage records derived from the related birth records. In this case the type of approach is not entirely clear, because the hypothetical marriage records are themselves derived from the birth records and are therefore part of the original records, which may be an argument to classify the basic linkage step as fully attribute-based pairwise comparison. Alternatively, the derived date attribute can also be viewed as a normal attribute of a dis- tinct hypothetical marriage record which is assigned together with the name attributes as part of the formation of the new marriage record from the original birth record, again resulting in classic attribute-based comparison. However, the final reconstruction step (as illustrated in Figure 7.2d) is clearly both relational and incremental, as the link be- tween the 1848 birth certificate and the 1846 actual marriage certificate is based not only on the attribute similarity between the marriage couple and the parent couple but also on the previously established link between the marriage certificate and the 1846 birth certificate, which is found to be consistent to the new link. The difference between naive and collective relation entity resolution in [10] seems to be a somewhat gradual distinc- tion, as the latter uses not only information from nodes with distance 1 as attributes (as in naive relational linkage) but also information from nodes at larger distances.
Although there are similarities to the method of [10] (and related approaches), the general problem of collective entity resolution differs from the problem of family recon- struction, and accordingly the approaches that can be applied are different. Collective relational entity resolution is based on the notion of clustering (or matching in general) of multiple references to the same entity using overlap in relational information. This approach is useful in, e.g., linkage in databases of scientific papers or comparison of consecutive historical censuses, where relations between entities may occur multiple times and multiple entities may be linked simultaneously in the source documents (such as a scientific paper with several authors or a family in a census record with two or more children). However, in civil registry databases such as Genlias the relations are much more sparse. The example task of linking birth certificates to marriage certificates as used in this chapter does not involve duplicate relations at all. A family reconstruction is
defined as the linkage of a marriage certificate to a set of birth certificates where the mar- riage couple and all the parent couples refer to the same entity (note that the two people in a couple are considered a single entity in this case), using only the relation between a child and a parent couple. Because a birth event is unique, this relation is necessarily unique as well. Additionally, each relation consists of exactly two entities (there are no
hyperedgesin the terminology of [10]). Collective entity resolution based on clustering
of recurring or partly overlapping relations is therefore not possible for this linkage task. In terms of the domain: entity resolution between children is not possible because the children are distinct, and entity resolution between parents cannot be performed using common neighbors or similar structural graph properties because there are no common neighbors or any other cluster similarities available.
As an alternative to constraints on graph structure the current approach uses domain- based consistency in event sequences as a measure of linkage quality. This is an exten- sion and a deviation from previous collective entity approaches which is useful in case relations are sparse but the domain still has clear collective properties.
The design of the algorithm is influenced by the domain of Dutch 19th century civil certificates. However, the event sequences are incorporated into the algorithm in a general way, which is also applicable to other domains. Consider for example an online travel agent interested in identifying repeated customers in his sales records. As domain constraints a customer is unlikely to book overlapping trips, or to have booked two trips only with several years in between. This can be combined with plug-in similarity measures on person names or, e.g., destination characteristics. An implementation of this record linkage task is relatively straightforward using the presented method.
In future work, the candidate selection process can be refined to increase the cov- erage of the method. The consistency model can be extended to improve accuracy of the matching, for example by imposing a constraint that a child may not have the same name as the other (living) children in the family. Additionally, the influence of vari- ous threshold values could provide further insight into the problem of historical family reconstruction as well as the group linkage problem in general.
Link validation using Gedcom
databases
This chapter describes parsing of genealogies in the legacy Gedcom file format. The parsed genealogies can be mapped to Genlias certificates in order to compare links pro- duced by algorithms to links contained in the genealogy. The chapter is based on the paperComparison between historical population archives and decentralized databases
[115].
8.1
Introduction
In the historical demographics and genealogy domain, research data can be collected from centralized databases such as a historical census or civil registry. Alternatively, decentralized data can be collected from, e.g., personal archives or local organizations. Complementary and conflicting information between these sources can be valuable for research if the overlap, i.e., matching records, is correctly identified. This chapter de- scribes a method to discover matching records in centralized and decentralized data for the problem of family reconstruction. The centralized data consists of Genlias certifi- cates. As a source of decentralized data a manually compiled family tree in the Gedcom
format is used. An overview of related work is presented in Section 8.2. Section 8.3 describes the differences between Genlias record structure and the Gedcom format. Sec- tion 8.4 provides a mapping procedure between the different data formats. In Section 8.5 the matching procedure is explained at the conceptual and technical level. Section 8.6 provides a verification procedure and results for a test database. An application of the matching in a family tree visualization tool is provided in Section 8.7. A conclusion and directions for future research are provided in Section 8.8.
The most important concepts used throughout this chapter are listed in the follow- ing definition. Concepts from this definition which have also been used in previous chapters are repeated here for convenience and explicitness of definition.
Record. Unit of matching and linkage. A record refers to a Genlias certificate (Sec- tion 8.3) or a Gedcom certificate reconstruction (Sections 8.3 and 8.4), unless stated otherwise.
Record match. A pair of records that refer to the same event (birth, marriage or death). Record link. A pair of records that refer to related events (e.g., birth and death of the same person).
Field similarity measure. Similarity between field values, e.g., number of days be- tween dates.
Record similarity measure. Similarity requirements for selected fields and relations between the requirements.
Name sequence. Concatenation of person names from a record. Person name. Single name, i.e., given name or family name.