Cabinet Office: Automated Digital Document Review
An algorithm to assist in the identification of digital records of long-term historic value and digital information assets that hold no long-term value.
Tier 1 – Overview
Name
Automated Digital Document Review
Description
Government departments can generate huge volumes of digital information. This needs to be sorted into records that need to be retained as the official record and information that should be destroyed because it is redundant, outdated, trivial or ephemeral in nature, or has reached its retention period. It is important that government is able to identify and select information of value for the record in order for it to comply with the requirements of the Public Records Act 1958.
To achieve this, large volumes of unorganised, legacy digital information would need to be read by records reviewers in order to identify information that should be retained as a historic record, and what should be subject to permanent destruction. The algorithm is part of a disposal methodology for digital information that allows the rapid review of high volumes of digital information that would otherwise be an extremely onerous and expensive task using traditional human review methods. The algorithm sorts information using a mixture of classifications and language patterns/key words. The outcome of a review can then be visualised to support human officers to make decisions about what information to retain.
Human operators input the instructions into the software running the algorithm, and are able to review its proposed actions before confirming and executing these, or re-running the review with a revised set of parameters.
Deletion would involve the human operator running a deletion command across the information collection in accordance with the recommendations flagged by the algorithm. The diagram at section 3 illustrates the stages of filtration that disposal processes include and the algorithm itself is shown at section 2 below.
Website URL
N/A
Contact email
dkim-cdio@cabinetoffice.gov.uk
Tier 2 – Ownership and Responsibility
1.1 Organisation/ department
The Cabinet Office
1.2 Team
Digital Knowledge and Information Management Team
1.3 Senior responsible owner
Head of Digital Knowledge & Information Management
1.4 External supplier involvement
Yes
1.4.1 Supplier or developer of the algorithmic tool
Automated Intelligence Ltd
1.4.2 Companies House Number
NI603151
1.4.3 External supplier role
Automated Intelligence Ltd has supplied the software in which we programme our script and through which we operate our disposal methodology. This tool is a specialised elasticsearch based analysis platform called AI.Datalift. The tool provides visualisation of analysis and can be programmed to execute pre-set policy rules following analysis. It can identify sensitive information such as passport numbers, or addresses using artificial intelligence to assist analysts in understanding their unstructured data.
1.4.4 Procurement procedure type*
Call off from a G Cloud framework
1.4.5 Terms of access to data for external supplier*
The supplier gains access to the data via a web crawler that makes an exact copy in the supplier’s system, where it can be subjected to analysis and treatment.
The Authority (the Cabinet Office) requires the Supplier (Automated Intelligence Ltd) to provide the following products and services:
- Data analytics tool that is programmable so that data can be classified as either ROT (Redundant, Outdated or Trivial) or as valuable
- Data analytics tool that is able to action a deletion on data so designated.
- Data analytics tool that is capable of classifying and searching data according to:
- Date of creation
- Date last modified
- Date last accessed
- File format
- Keywords (exact phrase or with Boolean operators applied)
- Duplicates / de-duplication
- And a matrix of any or all of the above in combination
- Data analytics tool that can assist with content analysis of documents and be able to present:
- A list of the documents discovered
- The metadata of the documents
- Where keyword search is used, a view of the actual document discovered
- Data visualisations of queries, showing volume against the parameters of queries applied.
- Data analytics tool that can integrate and sync with CO systems for ongoing analysis (firstly in a Google environment, but not limited to) The following technical standards must also be upheld:
- Minimum Cyber Security Standard
- ISO/IEC 27001
- NCSC Cloud Security Principles
- Cyber Essentials Plus and included within the service description provided under the relevant service ID.
In addition, the following standards should be adhered to to the extent they are appropriate and agreed as such by both parties, such agreement to be reached within a reasonable period of being under contract): * Digital Service Standard * Technology Code of Practice * Web Content Accessibility Guidelines with conformance not below level AA.
Tier 2 – Description and Rationale
2.1 Detailed description
The algorithm provides a means to automate the analysis of high volumes of digital information so that records of historic or corporate value can be retained and redundant, outdated and trivial information deleted.
We have developed an understanding of the key-words or phrases commonly used by civil servants in documents that are recognised as important records. Conversely, patterns of language can be constructed that are commonly found in redundant, outdated and trivial information (known as ‘ROT’) which is of little or no value.
These words or phrases (also known as ‘terms’) can be identified in documents using search engines. The words or phrases identified are collated into a list called ‘The Lexicon.’ Terms in the Lexicon are weighted (i.e. given a value) so that when the search engine discovers a term in a document it is able to determine its value as a historic record.
The Model
When the algorithm is applied to a collection of digital documents, the following categories are defined:
- File extension types split into:
- File extension types that are weighted towards retention;
- File extension types that are weighted towards deletion;
- File extension types that are indexable (i.e. capable of being read);
- File extension types that are not indexable;
- Documents where the lexicon terms is indicating historic value.
- Documents where the lexicon terms is indicating ROT.
- Documents where the lexicon of terms is indicating both ROT and value terms. To illustrate where these parameters fit into the model, the diagram below gives a visual representation of how each of the six classifications are applied and demonstrates how 1a and 1b (categorising file extensions) divide and treat files differently.
The file types that are most likely to contain information of historic value must contain more lexicon terms that indicate ROT than default delete files in order to be put into a deletion classification. This is because through the collective experience of records management professionals combined with dip sampling data, we know that the proportion of documents that fall into the default retain file types generally have a prevalence of valuable files of c.15%+, whilst for those that fall into the default delete types the prevalence of valuable files is between zero and 1%.
It is important to emphasise that the file type only contributes to how the full lexicon of terms is applied and it is still the frequency and type of terms that arise in the files and their metadata that determine whether deletion or retention is recommended by the algorithm. The only exception to this is .pst files which are always retained. A detailed breakdown of the characteristics of files in each classification and an example of a typical file that would fall into each one is provided below.
Note: Wildcard Definition
A wildcard is a special character that can stand in for unknown characters in a text value. If a file’s content is not a wildcard then it has no indexable content i.e. no words detected inside. If the file content is not a wildcard but the extension type should be indexable, we know the file does not contain useful information.
Classification A: Size of Zero
- Size zero files that are completely empty. (Example of this type of file: completely empty file or any extension type.)
Classification B: Empty
- File content is not a wildcard.
- File content is indexable file type and therefore contains no content.
- The file is not a .pst. (Example of this type of file: a word document with no content except one space character.)
Classification C: Not Indexable Default retain deletions
- File content is not a wildcard.
- File extension is not indexable (NOT doc, txt, docx, msg etc.)
- The file is not .pst.
- File extension IS one of the default retain (eg pdf, jpg, tif, tiff)
- Filename & Path Analysis: No value terms picked up AND at least one ROT term picked up (Example of this type of file: a pdf with the file title: ‘RE inv: August workshop’)
Classification D: Not Indexable Default delete Deletions
- File content is not a wildcard.
- The file is not .pst.
- File extension is not indexable (NOT doc, txt, docx, msg etc.)
- File extension IS one of the default delete (eg ico, wp, sql)
- Filename & Path Analysis: No value terms picked up OR a ROT term picked up (Example of this type of file: SQL database file with file title: ‘dneowfjeiofsnco238fekrn34’)
Classification E: Indexable default retain for deletion
- The file is not .pst.
- File extension is indexable (doc, txt, docx, msg etc.)
- File extension IS one of the default retain (eg pdf, jpg, tif, tiff)
- Filename & Path Analysis: No value terms picked up AND at least one ROT term picked up (Example of this type of file: an email .msg file containing no value terms and the terms: ‘admin’, ‘stuff’ and ‘template’.)
Classification F: Indexable Default delete for deletion
- The file is not .pst.
- File extension is indexable (doc, txt, docx, msg etc.)
- File extension IS one of the default delete (eg. ico, wp, sql)
- Filename & Path Analysis: No value terms picked up (Example of this type of file: a webpage with no value terms in the content, title or filepath.)
2.2 Scope
The methodology, the algorithm and the lexicon have been created to ease the burden on archivists and records managers by automating part of the repetitive decision making process of identifying files suitable for retention as part of a disposal operation.
The algorithm is intended to be applied to collections held by the Cabinet Office (or any other organisation) for the purposes of identifying files to dispose of in line with the organisation’s destruction and retention policy. The algorithm is designed for use on such collections where: * There is a suspected mixture of both R.O.T. (Redundant, Obsolete or Trivial) files and files of historic value that must be retained. * The collection is too large to identify which files to dispose of and retain manually. * A small risk tolerance for files of historic value being incorrectly disposed of is acceptable. * It is acceptable to create a temporary copy of the files in the Automated Intelligence tool AI Datalift in order to conduct the analysis.
If the collection meets these requirements then automating disposal via the lexicon methodology using the algorithm may be a sensible option.
The algorithm is not intended to be used as part of a sensitivity review process.
2.3 Benefit
The benefits of using the Lexicon model to automate digital information disposal include:
* Efficiency/cost avoidance: the algorithm and overall methodology automates previously manual processes that, in the context of digital records management, are no longer a viable or sustainable approach.
* Consistency and accuracy: automation is consistently more accurate than humans at making decisions about the records value of a document; our tests showed that human error was ~1% but the automation showed an error rate likely to be < 0.6%.
* Speed: We estimate that a human reviewer could reasonably review up to 200,000 documents per annum. With automation we could achieve a review of several million files with no increase in human resource required to accommodate the higher volumes of files to be reviewed.
2.4 Previous process
The previous method of disposal before the creation of the lexicon model consisted of digital archivists manually reviewing files both at a folder level and individual file level. This method was fairly accurate but extremely slow compared with our now automated solution, and was exclusively carried out using paper documents. Review of digital documents had not previously been attempted at scale. The human reviewers would take into account the content of the documents and make a decision as to whether the file should be disposed of or retained and reviewed again at a later date. Even with expert reviewers applying the destruction and retention policy to the best of their ability this process of manual review was sometimes subjective. Also, in many cases, no records were kept of the reasons for destruction decisions and the error rate was therefore unknown. The process of human review is very slow compared with the automated approach.
2.5 Alternatives considered
Machine Learning An approach applying machine learning was considered. However, we did not possess a large enough labelled training dataset to make supervised ML a viable option. An unsupervised learning model such as a clustering machine learning algorithm could have aided in categorising documents into different groups but would not have been able to distinguish which of those clusters should be put forward for retention or deletion. Another reason this approach would have been difficult to implement is a lack of expertise and skills in this area within the existing team and headcount restrictions.
Tier 2 – Decision-making Processes
3.1 Process integration
Our digital disposal system ingests usually unstructured legacy files from business units and applies the disposal process. This results in a smaller number of historically relevant files that can be moved to our Cabinet Office archive and eventually to The National Archives.
The algorithm is applied using the lexicon at the ‘aggressive reduction’ stage of our disposal process.
3.2 Provided information
The output of the tool is a report detailing the recommended files to be deleted. A digital archivist can review this report, analyse and test the final results to ensure the application of the lexicon on the collection is in-line with the standards agreed by Departmental Governance, which is that less than 1% of files are incorrectly identified for deletion.
Details of what files have been deleted should be added to the deletions report and emailed permission should be obtained from the DRO prior to actioning these deletions. Alongside the deletions report a copy of the elasticsearch code should be saved to ensure a record and logical reasoning for why deletions have been actioned is preserved for any future audits.
3.3 Human decisions and review
The decisions required to be made by humans include:
- Judging that the collection is suitable for the application of the lexicon to it, this involves verifying that:
- There is a suspected mixture of both ROT (Redundant, Obsolete or Trivial) files and files of historic value that must be retained.
- The collection is too large to identify which files to dispose of and retain manually.
- A small risk tolerance for files of historic value being incorrectly disposed of is acceptable.
- It is acceptable to create a temporary copy of the files in the technology tool in order to conduct the analysis.
- Reviewing the search terms used within the lexicon and conducting sense-checking tests to ensure the terms used are not returning anomalous results. This is because all collections are different and use of certain language changes over time. A term that significantly increases the likelihood that a document is valuable in documents created in 2005 does not always have the same result on files created in 2022.
- Ensuring the algorithm is performing to the minimum acceptable level as approved by departmental governance, which is 1% or less of files reviewed are incorrectly identified for destruction.
3.4 Required training
The Data Analyst completed a Data Science 3 month intensive bootcamp and ElasticSearch training courses to upskill in Python (required for data cleaning and analysis of test results) and ElasticSearch (the language the lexicon is programmed in).
All team members involved with the project attended learning sessions hosted by the supplier of the data classification tool used to run the algorithm in which they learned how to operate the in-built analysis tool.
3.5 Appeals and review
Once a destruction decision has been made and a file deleted, this is a hard deletion and therefore by definition the file is non-recoverable meaning an appeal is not possible. The elasticsearch code and all terms within the lexicon will be saved along with the deletions record so in the case of an appeal or Freedom of Information Act request we could provide justification as to why a certain file was deleted.
Tier 2 – Technical Specification and Data
4.1 Method
The method used is a deterministic automated language model. The method is a scoring system using ElasticSearch which assigns a relevancy score to each file based on:
Term Frequency. How many times a term is present in a document or document metadata such as filename and filepath. The more times a term appears, the more relevant the document is. In this case, the relevancy is how likely the file is redundant, obsolete or trivial and therefore should be deleted.
Inverse Document Frequency. The more documents in the collection the lexicon is run over that contain a term, the less important and impactful it is. For example if we put the term ‘the’ into the lexicon it would not have any notifiable impact because virtually every document will contain the word ‘the’. This feature protects the lexicon from certain types of bias, e.g. where common phrases, that add little or nothing to the calculation of the historic value of information, can be discounted.
Field Length. If many search terms appear in a very short document, then this document has a high density of terms and this is treated as more significant than a 5000 word document with the same number of search terms inside. This also weights the appearance of search terms inside filenames as a stronger indicator as the field length of document titles tend to be shorter than the contents of documents. These components contribute to the overall relevancy score assigned to files. Each file receives this score and then a threshold is decided based on review and dip sampling of files with varying relevance scores. Decisions of this threshold are reviewed on a collection basis with the aim to minimise the number of files incorrectly deleted.
4.2 Frequency and scale of usage
The algorithm has been used to review 5.1 million legacy files to date. The team is currently using their disposal methodology to review a further ~300,000 files which will be completed in this financial year (2023/24). After this time, the algorithm will be used on an annual basis to review the stream of files surrendered to the Digital Knowledge and Information Management team from Business Units. The number of files received in the future is unknown but is likely to be approximately 30,000-80,000 files per year.
4.3 Phase
Production
The methodology, which includes the algorithm and lexicon, was created over a period of months from January 2022 to June 2022.
The lexicon was approved for use on legacy Cabinet Office files by departmental governance on the 30th June 2022.
The first lexicon/algorithm informed deletions took place on the 22nd July 2022 and consisted of the permanent destruction of 1,663,180 files that were acknowledged as Redundant, Outdated or Trivial (ROT) deletions.
4.4 Maintenance
The Lexicon requires ‘tuning’ when applied to a new collection of files. This is because all collections are different and use of certain language changes over time. A term that significantly increases the likelihood that a document is valuable in documents created in 2005 does not always have the same result on files created in 2023.
The frequency of the tuning of the lexicon is dependent on how many different collections the DKIM Lifecycle team analyse but there will be a minimum of an annual review. This relates to the frequency of the annual ‘Spring Clean,’ an acquisition process that involves the transfer of documents older than 7 years from all business units to the DKIM. The intention is to use the lexicon to aid the digital archivists in the review of these transfers once all legacy datasets have been analysed.
4.5 Model performance
Testing Method
In the pilot, the method used to test how effective the lexicon was at correctly identifying files to dispose of and files to keep, was by creating a random sample of labelled files from the collection and then applying the lexicon to them. The percentage of files incorrectly identified was the estimate for the error rates of the model.
Types of Error Rates and How to Calculate Them
There are two types of error the lexicon can make: incorrectly recommending the destruction of a file that should be retained (Type 1 error, a false positive) and incorrectly recommending the retention of a file that we could dispose of (Type 2 error, a false negative).
See Table 1 in for error descriptions.
Sample Size
A good rule of thumb for dip sampling a statistically significant number of files is either 10% of the total number of files in the collection or if the collection is so large that sampling that many files is unfeasible, 1000 randomly sampled files can be used. If there is bandwidth to do so then increasing the sample size would be likely to produce a more accurate estimate of the error rates, which would be preferable.
See Table 2 in for sample size criteria.
Success criteria
The purpose of producing the estimates for how effective the version of the lexicon used is on the collection in question is ultimately to see whether the model can be used. The following levels of success criteria were agreed upon by departmental governance.
- Type 1 Error. Success criteria with regards to over deletion (deleting files of historic value that should have been retained) was approved by departmental governance . The value must fall below 1%. If the type 1 error rate is higher than this, the lexicon must be tuned further. See Equation 1 in for Type 1 Error calculation.
- Type 2 Error. The acceptable level of under deletion (retaining files that are redundant, obsolete or Trivial is dependent on the collection and results. No exact figure has been agreed by a governing body. The type 2 error needs to be risk assessed per collection and version of the lexicon, taking into account the proportion of value suspected in the collection and how valuable this is likely to be. This will also vary per collection as there will be varying proportions of value and ROT files in different collections. See Equation 2 in for Type 2 Error calculation.
- Relationship between Type 1 and Type 2 Error. There will usually be an inverse relationship between the Type 1 and Type 2 error rates. The more cautious a model is at recommending disposal, the smaller the type 1 error will be, but this will increase the Type 2 error.
4.6 System architecture
N/A
4.7 Source data name
N/A
4.8 Source data description
The source data consists of unstructured data surrendered to the DKIM team from CO business units. The data classification tool used to deploy the algorithm extracts the following information from the unstructured data in order to run the lexicon model:
- File title
- Historical file path (if available)
- File content (if indexable - eg. an image file contains no words so field is blank)
- File creation date
- File last modified date
- File mimetype
- File extension type
4.9 Source data URL
N/A
4.10 Data collection
Legacy documents from business units are acquired by the DKIM Team so that they can ensure compliance with the Public Records Act 1958.
4.11 Data cleaning
The following fields are extracted from the unstructured data (files):
- File title
- Historical file path (if available)
- File content (if indexable - eg. an image file contains no words so field is blank)
- File creation date
- File last modified date
- File mimetype
- File extension type
Data cleaning techniques such as removing any outlier files from the review or handling missing data is not applicable. The data classification tool used to run the algorithm detects whether a file has missing metadata such as being non-indexable eg. an image or video file and treats these accordingly.
Prior to running the algorithm, the archivists will prepare the data set through removing any obvious areas of ROT through a high level review. The archivists utilise the department’s Records Selection Policy to identify themes in the collection that are either required to be retained or not.
4.12 Data completeness and representativeness
As the nature of the problem is to make decisions based on all files the process is able to handle a variety of different scenarios including missing or corrupted data just like a human reviewer would. The goal of the creation of the lexicon is to mimic the decision of an expert reviewer, who would always seek to make the best decision possible with the information available. As there are generally no files with missing file names or file paths, the only ‘missing data’ to handle is file content.
File content. In the absence of file content the algorithm will identify that file for deletion where the size of the file is zero. This is because a file with no content does not contain any useful information and therefore does not need to be retained.
4.13 Data sharing agreements
No data sharing agreements are in place beyond commercial contracts.
4.14 Data access and storage
A temporary copy of personal data is made in order to enable the analysis of files. Once the analysis is completed a hard deletion of this temporary copy is actioned. This means the files from that copy are not retrievable after the conclusion of analysis.
One of the goals of the use of the system is to enable identification of personal data that is not required to be retained as part of the official record, so that files containing personal data that should be removed are not retained in the Cabinet Office archive.
Only members of the DKIM team that require access to the tool AI Datalift are granted an administrator account with access to the information being analysed. Team members hold appropriate security clearances.
Tier 2 - Risks, Mitigations and Impact Assessments
5.1 Impact assessment
A DPIA was completed on 14th June 2023 Summary: The risk rating is Medium. The residual risk is considered LOW. There are a number of risk mitigations in place for this process. Each of them are designed to limit the potential of negative impacts on the processing of the data. Despite the lack of clarity of the potential of the inclusion of special categories of data, the process is compliant and within the expectations of the public. Also the technical and organisational controls strictly limit the potential risks As a consequence the residual risk is considered LOW.
The risk of over retention of personal data is possible but unlikely as obvious collections of personal data (e.g. HR files) will have been sifted out in the preparation phase of each disposal. As the purpose of the algorithm is to identify records of value for long term preservation, the archiving of personal data in the public interest is accepted within the GDPR as legitimate.
5.2 Risks
The challenges of using automation in this space are:
- Transparency - automation processes need to be understandable, with a clearly agreed margin for error. We have therefore engaged in peer review through discussing our approach with The National Archives, who are supportive. Our automation pilot achieved an accuracy rate of at least 99.4%, which proved to be better than a manual review process.
- Trust - any automated approach needs to be demonstrably trustworthy in arriving at consistently good outcomes. It is important to note therefore that retention and deletion ultimately remains a human decision and are not automated, but the automation produces fast analysis and visualisation to allow human decision making to take place at scale and at pace.
- Repeatability - While the lexicon based approach allows us to repeat the same methodology in any information collection, we are aware that all collections usually have some unique characteristics. Consequently our processes will dictate that before the automation can be applied to a collection, it must be ‘tuned’ following a scoping exercise carried out by our team of expert digital archivists.
- There is a risk that running the algorithm results in either the destruction of important records or retention of ROT. This risk can be mitigated by:
- Setting an organisational risk appetite. Cabinet Office’s modelling demonstrated that an accuracy rate of at least 99.4% could be achieved, which is better than the performance of comparative human models;
- Modelling and testing prior to disposal to ensure that the terms in the lexicon are valid and correctly weighted; In Cabinet Office this involves running a test review and measuring how close the outcome is to the 99.4% baseline;
- Weighting terms in the lexicon: this will depend on the risk appetite of the individual organisation. A risk averse organisation may place more emphasis on weighting in order to resolve ‘grey areas.’
Updates to this page
Last updated 29 February 2024 + show all updates
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Republishing to change order of records in finder
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First published.